1.0 Amal Carburettors.

Date: Wed, 6 Jul 1994 13:39:26 +0800
From: Jamie Hamilton <jamieh@uniwa.uwa.edu.au>

Subject: Amal or amyl?

P.S. I've noticed that most people, at least around here, pronounce Amal with the accent on the first syllable: "A-mul". However, since the word was derived from "Amalgamated [Carburettors]," shouldn't it be pronounced "uh-MAL"? Does anybody know the history of this?

In Australia and Britain it has always been pronounced with a soft 'a'. As in animal or amyl-nitrate. The history comes from the peculiar way you North Americans customise the English language. Any UK members will be quick to reassure you however that the reputation of Australians in this regard is less than pristine so don't take offence ;-)

While we are off the main thread- I read with interest another side comment some while back from someone who expressed surprise at seeing an outfit with the sidecar on the left. I guess its the same as cars, though I never realised it. I have never ever seen a sidecar on the right hand side down here.
 

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1.1 Renovation.

Date: 1 Jul 1994 10:54:23 -0500
From: John Knobel

With all the discussion of jetting problems with the Amals - is there ever a cure? Getting a good tickover with the Norton seems next to impossible. Slides are not visibly worn, carbs totally cleaned and all passages blown out. New: air cleaner, plugs, Boyer, wires.

All my other bikes I was able to get to sit there and idle forever. Two-strokes, four strokes, singles, twins. Even race-type bikes running big Mikunis ( Three 34mm's on an 850 triple)

So, is it the Amals? Would Amal Mk IIs do the trick? Mk 1.5's?

It's nothing I can't live with , but just thought I'd enquire. - John

From: Ralph Merwin
Date: Fri, 1 Jul 94 8:46:24 PDT

John Knobel writes:

>With all the discussion of jetting problems with the Amals - is there ever a cure?

I'd suspect the carbs. To quote Andrew Wolf: "Someone asked how to tell if a Amal carb is worn, well if it is the original, has not been resleeved, then it is WORN."

I have a Mikuni carb on my Norton. It'll idle smoothly as long as I let it run. John Pinkham recently had his Amals resleeved and I think he has a smooth idle as well. You might want to consider having your carbs resleeved at Lund's...

Ralph

Date: Fri, 1 Jul 94 13:31 EDT
From: Latte' Jed

>I'd suspect the carbs. To quote Andrew Wolf: "Someone asked how to tell if a
>Amal carb is worn, well if it is the original, has not been resleeved,
>then it is WORN."

I'd like to amend this: "If it's not brand new, it's worn". The design of the Amals is fine, they're just made of shit metal. The wear isn't just the slide, the carb body wears too, and you can never tell what some previous owner did - a lot of people will replace just the slide when they can see that the slide is worn, which doesn't help much. I've been going through all our bikes having all the amals re-sleeved as I can afford it, some needed it more than others but they all benefitted from it.

Oh yeah, new needles too, they're cheap enough that it's good insurance. They generally don't show the wear, so unless you know what to look for (I don't) they look ok.

Date: Thu, 27 Oct 94 09:16:05 EST
From: Nigel Nicholson

Last weekend I bought a 73 Trident T150V. The previous owner had recently replaced the exhausts. With only a few miles on them, the left pipe (#3) is bright blue, the centre pipe (#2) reddish, and the right pipe (#1) pale yellow. On warming the engine last night, I noted #3 was noticably hotter than #1.

Pulling the spark plugs, I observed that #3 looked fine and #1 was very sooty. I cleaned up the plugs and switched them. I also backed out the adjustment screw on #1 so that it showed about the same amount of thread as #2 and #3.

The pipes then appeared to heat more equally after a few minutes idling. I can only get the warm engine to idle as low as @ 1,100 rpm without stalling out. The workshop manual claims 500 rpm is optimal.

Can anyone suggest how best to balance the idle revs? I'd like to avoid the trial-and-error approach...

Nigel Nicholson

Date: Thu, 27 Oct 94 10:40:53 EST
From: nicholsn <nicholsn@optec.army.mil>

Thanks, Mike. This coming winter would be a good time to send the carbs out for sleeving. Can you recommend a shop? What is a reasonable price? Are there alternatives to sleeving? Nigel

Your high idle smacks of sloppy carb slide disease! Tridents most definitely benefit from slide sleeving, and my '73 was done about three years ago. 500rpm idle no problem.

Date: Mon, 19 Dec 1994 21:15:49
From: Nancy J Caputo

The following letter appeared in CA Bike, Dec., 1994. I've excised portions. Written by Mike Gaylord, resleeve specialist in WA.

"The author [columnist 'Bib'] prescribed the method of flattening a bowed flange by, "Rubbing it on emery over a surface plate." ... Is "that" method appropriate for you today?

Today we have better tools. . . . Having personally straightened thousands of Amals, I feel qualified to discuss the cause of bowed flanges, the proper cure, and the injurious results of crude methods.

We note at our facilities, that the only flanges not requiring straightening during reconditioning, are from low-mile Nortonís and BSA triples. At least one assembler at BSA had the "touch", and understood that it is not necessary to chin yourself on the mounting nuts.

Norton mounts their carbs straight to a manifold and the flanges stay flatter than the flanges of carbs that are mounted against insulator blocks, as was the practice of most other British makes.

The insulator block is of fibrous material that will crush under excessive pressure. An unskilled mechanic will install a carburettor with crushing pressure almost every time. The crushing of the insulator allows the carb flange to bow. As the flange changes shape, stress is created in the casting, causing the walls of the mixing chamber to go out of round. In severe cases, the slide used therein will bind and stick . . . . a very dangerous situation.

Flycutting, or lapping the flange does not correct the distortion in the mixing chamber, but does spoil the casting by thinning and weakening the flange, while allowing the distortion to remain.

Internal distortion is corrected and flanges are straightened with special fixtures. The process is the first and most important step in our reconditioning sequence, as it restores the integrity of the casting and retains the original strength.

If you are dealing with a bent carburettor body, have it straightened. Never lap or flycut a flange, as metal removal methods do irreversible damage.

Also, an insulator block that has been crushed should not be reused. The block may appear flat, but it will be spongy instead of firm in the flange area, and will no longer afford a carburettor flange the necessary support and a straight flange can be easily ruined by such an insulator.

Very truly yours,

Mike Gaylord

Also in the same issue: 1973 Norvil Commando, 850 factory race prep. Only 400 miles on full mechanical/cosmetic restoration. Rare and beautiful classic. Priced at only $7,495. (714)854-2049.

I beg your pardon?

Cheers,

Lou

From: Lew Hosier
Date: Mon, 04 Jul 94 00:31:43 EDT

Iíve heard a shop called Lunds mentioned several times in Britbike. Are they prompt and reliable for having Amals re-sleeved? If so could someone tell me how to get in touch with them?

I recently picked up a set of 32mm at a show for $50.00 complete with cables. They looked excellent (they fooled me because one had a new slide). So I thought I could try them out. If they were any good possibly I could save the cost of re-sleeving, and if not I could at least nurse my Commando along while my originals were being rebuilt. Needless to say they aren't in any better shape than my old ones except they seem to have some new parts, 1 slide, floats and possibly needles (no chatter marks).

Can I use the good looking needles (#107 needle jet) to replace the rough looking ones from my original carbs(#106 needle jets)? i.e. Are the needles all the same and only the needle jets different?

I soon found that they were not originally from a Commando. I had to file the bodies , at the blank throttle stop boss, to get them to fit closely together enough to mount. I switched the jets and needles from my old carbs( 220 main and 106 needle jet ). But the bike ran pretty lean at hiway speeds and a change to a 240 main and needle clip to the richest position didn't help much. It always ran kind of lean at hiway speeds, with my old carbs, so I'm wondering if I should change from a #3 slide to a #3 !\2 (as recommended in some manuals) before I send them out for re-sleving?

The idle mixture is also screwy with one side lean and the other rich despite a treatment with colortune. My old carbs have no pilot jet but a brass restrictor built into the idle air passage, the show carbs have just a #26 pilot jet.

If any of you guys (or gals) have any comments, particularly as to weather I should invest in a new # 3 1\2 slide(I assume that the slide and the carb are custom fit during the rebuild and you cant change slides later), I'd really appreciate it.

I am also really curious as to what kind of bike these carbs came from?

They are:

Amal 32mm concentrics ( L + R )

#3 slide
#107 needle jets
#26 pilot jets
#200 main jet

Thanks,

Lew Hosier

71 Comando Cafe

Date: Tue, 25 Oct 94 07:45:07 EDT
From: Steve Welk

What's the general consensus on having concentrics bored/sleeved? Talked to Walt Lund in Oregon who has apparently done a lot of these. Price seems reasonable, esp. in qty. Do they wear out as quickly as the original? I was hoping he'd put some kind of sleeve in the carb body as well as on the slide to reduce wear, but that's not the case. Any experience w/ Lund or anyone else for that matter?

I seem to recall Pete Serrino mentioning experience w/ this recently.

From: maloney
Date: Mon, 23 May 94 10:06:36 EDT

The bore and sleeving job on my Commandos Amal concentrics has made a *big* difference. It is now a starter on the first kick. And it idles. Even though there were only 7500 miles on the clock, the Amals were worn out. Lunds does a beautiful job for $105 US for the pair. Mr Lund is a interesting fellow to talk to also. Says he's done about 500 carb jobs so far.

Date: Tuesday, 25 October 1994 10:21 ET
From: Michael Read

One word of caution regarding the sleeving of Anal, er Amal carbs. Make sure the the slide is sleeved with a softer metal than the carb body! The slides are far cheaper to replace when they finally wear out than the bodies are! So, at 100,000 miles when you need to re-sleeve, just toss the slides and have the new ones sleeved. If done in this fashion, the body should last indefinitely.

My slides were sleeved three years ago with aluminum (forget the spec) and no wear has occured on the bores since, and the slide sleeves still look brand new. (The carb bores were machined true at the same time for a close tolerance fit.)

Hope this helps,

MJR ('73 Triple Threat)

Date: Tue, 25 Oct 94 07:26:27 -0600
From: Your Name Here

I have had my Carbs done by Lunds. Great deal, cheap and FAST (typically1 week, this man knows about customer service)

Look at the inside of a carb and you should understand the impractibility of sleeving the inside of the carb. To have a dimensionally stable sleeve would require a very thick sleeve and there just ain't the room for it.

Lunds uses a steel sleeve on the slide. I have used my Monoblocs for 2 years and the wear is negligible. However I have put less than 2k miles on.

I look at it this way.

The original carb was made to a price. The carb body and the slide were of the same material. This is bad as the 'natural' lubricity between similar materials is usuallly very poor.

The boring of my carbs gave me 'new' performance for very little money. That he sleeves the slide with steel provides two dissimilar materials and may provide better lubricity. (also may increase galvanic reaction, so I coat my slides with oil when I store my bike).

Even if the rebored carbs have no greater life than the original, it still is a cheap way to extend the life of the carbs and avoid the large cost of new non original carbs.

Do It and install viton tipped float needles, new needle jets and needles, you WILL be amazed with the results.

Andrew Wolf

Date: Tue, 25 Oct 1994 10:30:43 -0400
From: Pete Serrino

>What's the general consensus on having concentrics bored/sleeved? Talked to
>Walt Lund in Oregon who has apparently done a lot of these. Price seems
>reasonable, esp. in qty. Do they wear out as quickly as the original?
>I was hoping he'd put some kind of sleeve in the carb body as well as on the
>slide to reduce wear, but that's not the case. Any experience w/ Lund or anyone
>else for that matter?

Steve, In addition to Lund's, there is Fair Spares America (Phil Radford - steel sleeve), Triton Machine (Bruce Chessel - brass sleeve) Woodstock, Ont., and AMR (Mike Haracourt (sp?)) in Arizona who uses a chrome plated brass Mikuni slides. Probably others as well. As far as I know they are all good. Local folks have used both Fair Spares and Triton with good results. Some people have complained of rich running after releeving. Probably due to less air leaking past the slide. One thing to consider is your tuning options are narrowed since the stock slides will no longer fit. If you need to change the slide number for any reason it too would have to be sleeved. Perhaps the folks doing the work could give recommendations. eg if you normaly use a #3 slide maybe you would be advised to go with a 3 1/2 to compensate?? Comments appreciated.

Cheers,

Pete

Date: Thursday, 27 October 1994 07:37 PT
From: Robert Cachur

I had a set of really old and worn AMALs reworked by Bruce Chessel of TriTon Machining, Canada. This was at the suggestion of MJR (Trippple Threat). WHAT A DIFFERENCE A REBORE/SLEEVE MAKES!

Prior to the overhaul the bike ('72 Bonnie) would run at an erratic idle. I was constantly fiddling with the throttle to compensate. She now fires right up and maintains a constant idle. I no longer have to blip the throttle when coming to a hard stop. I love this bike more than ever. Thanks, Bruce & MJR ;-)

I can highly recommend Bruce's work... he's an enthusiast and has his head wired to his butt... nice guy. If you're interested please email me directly and I'll supply the vitals on an individual basis. I don't want the INTERNET police to get upset about advertising.

The slides are sleeved in brass.. looks sharp and slides soooo smoooooothly... real close tolerance, too. Only problem I have now is that the old dear pings at hard acceleration under load... gotta get this sorted out.

I'm restoring a T160 (about 85% completed) and did not fart around in the carb department... Three newly minted (and highly polished) AMALs will bring the Trident to life.

Life's too short do diddle with worn out AMALs.

Robert P. Cachur ;\

Date: Thursday, 27 October 1994 08:23 PT
From: Robert Cachur

Hokay:

Bruce Chessell

TRITON MACHINING
314 Knightbridge Rd.
Woodstock, Ontario Canada N457C4
519-539-7064 (H)
519-526-8600 (W)

He charges about $50-$60 (US) per carb.

FYI, I like my aluminum highly polished. I made the mistake of having all 5 carbs polished BEFORE sending them for sleeving/boring. Bruce likes to let the rebored carb body lay in carb cleaner for a day or so. Sure beats the hell out of that lustre. I recommend polishing the body AFTER machining. That is if you are as finicky as I am when it comes to detail.

BTW... if anyone is interested in someone who polishes aluminum so it looks like chrome AND is VERY reasonable... let me know.

Later,

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1.2 Tuning.

Date: Tue, 26 Jul 94 22:02:30 MDT
From: Patrick Fleming

My Norton is finally running but I have some problems with my carbs.

They are currently jetted to 220 but they run lean.

A little bit of choke seems to fix. Is this a bad thing to do. Should I try 230 jets?

Pat

Date: Fri, 29 Jul 1994 07:25:19 -0700 (PDT)
From: Peter Snidal

On Tue, 26 Jul 1994, Patrick Fleming wrote:

>My Norton is finally running but I have some problems with my carbs.
>They are currently jetted to 220 but they run lean.
>A little bit of choke seems to fix. Is this a bad thing to do. Should I try 230 jets?

1/4 to 3/4 throtle is controlled by the needle heights.

Date: 9 Sep 1994 09:47:13 -0500
From: John Knobel

Stephen Hill writes...

>Okay John, I'll draw you a picture. You see, in the Catholic model of electronic ignition,
>it all started with original sin. So when it breaks, and eventually it will, you deserve it,
>and there is not a damn thing you can do about it.
>
>And in the Protestant model of contact point ignition, when it breaks you fix it, regularly,
>thereby demonstrating your worth through hard work and receiving your rewards by
>enjoying your material possession.
>
>Myself, I am an atheist: I don't believe there is an ignition heaven.

Ignition heaven may be a diesel. But boring as all get-out and thereby indistinguishable from hell.

Amal question of the week. - My local Norton shop routinely changes the spray tubes from those installed in the 850 Commando's (the cutaway types) to 750 types. He suggested I try this before replacing needle jets and needles. Has anyone else tried this?

Also, I am going to run #3 throttle slides instead of 3 1/2's - anyone think this is a major difference? small? likely side effects?

The setup is - stock 73 850 Commando motor, 932 Amals, 750 pipes, standard Norton mufflers, K&N air filter, 250 main jets, 0.106 needle jets, the 4-ring needles with clip at top.

regards - John

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1.3 Spray Tubes.

From: Lew Hosier
Date: Fri, 09 Sep 94 20:21:54 EDT

Having the carbs resleeved had no noticeable effect on my Commando (except they don't rattle around anymore). But when I replaced the needle jet and needle, voila, thump thump thump.

Unfortunately the needle I bought has 4 i.d. rings. I'm going to try changing to the appropriate spray jet (the 850 type with the cut out), as outlined by Brian Slark in the latest I.N.O.A. newsletter, to see if I get an even more improvement.I'll let you know if anything happens.

Lew Hosier

72 Commando Cafe Ralf

Date: 12 Sep 1994 09:32:34 -0500
From: John Knobel <John_Knobel@star9gate.mitre.org>

Lew writes.....

>Having the carbs resleeved had no noticeable effect on my Commando
>(except they don't rattle around anymore).
>But when I replaced the needle jet and needle, voila, thump thump thump.
>
>Unfortunately the needle I bought has 4 i.d. rings. I'm going to try changing
>to the appropriate spray jet (the 850 type with the cut out), as outlined by Brian Slark
>in the latest I.N.O.A. newsletter, to see if I get an even more improvement.I'll let you
>know if anything happens.
>Lew Hosier

Funny, I just went the oposite way on my project 850 Commando!!!

I put on new Amals with the 750 spray tube and needle - the two ring one. #3 slide, 250 main jets, 0.106 needle jets - so far, it idles well and response seems real good. I haven't yet tried any high speed or plug checks though.

(It seems stronger than my other 850 with the stock setup, although this could be an effect of the the 1/4 turn throttle) This setup was recommended by my local Norton shop. He doesn't care for the cut-away spray tubes. He would recommend you get the right needles for the tubes you have.

Let me know how it works,

regards - John K.

Date: Wed, 25 Jan 95 14:48:40 GMT
From: Peter Azlan

Someone asked about the origins of sectioned spray tubes on Commandos.

Well, the only reason I have ever found for this comes from a conversation I once had with someone at amal, when I was fighting to resolve the Commando Backfire Bomber problem. The chap from Amal, nice man, said that they were getting concerned about the size of the main jets on the Commando's. Its like they had been evolving from the dominator, 750 Commando and 850 and with each streatch of the motor, they put the main jet size up. Now, the chap said that they developed the sectioned spray tube to increase fuel flow without increasing the main jet any further.

Sounds about right.

But remember, the needle with the 4 id rings goes with the sectioned spray tubes, and in my case, this needle also goes with a 260 Main Jet and 106 needle Jet.

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1.4 Needle Clips.

From: John Pinkham
Date: Mon, 12 Sep 94 7:18:08 PDT

Perhaps this was already thrashed to death, but since my mail system has been erratic, bear with me. Saw some talk about cracked Amal needle clips. If I'm not mistaken, the clips are manufactured with a break in the clip where it contacts the needle.If that's not so, the "new" clips I bought were either used or defective. Anyway, they seem to work alright "cracked".

John Pinkham

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1.5 Concentric Mark 1 & Mark 2 Carburetters.

Date: Fri, 30 Sep 94 10:34:42 BST
From: Peter Azlan

Chuck ponders on the purchase of a Mk1 or Mk2 concentric.

Well, I know a lot about the Mk1, as you may realise from posts on the subject but I am willing to admit I dont know a whole lot about the Mk2.

What I do know is:

To my mind, this arrangement sorts out the problem with the Mk1 and the solid aloy manifold, where heat from the head is conducted through themanifold to the carb, boilding the fuel and giving irratic idle and slow running, (especially in Town riding). If I had the choice, (I'm still getting over the shock of having to repalce the silencers), I would definately go for the Mk2, for the reasons stated above.

Date: Fri, 30 Sep 1994 15:39:50 +0000
From: Bob Cram

Peter Azlan says:

>The Mk1 1/2, is a Mk2 carb, but with an inlet flange the same as the Mk1,
>making it part compatable. It'll look more like the original thing.

I was always under the impression, probably mistaken by the sounds of it, that the Mk 1.5 was really just a Mk 1 with a better tickler. Am I wrong? If I am, what then is that Mk 1 with the better tickler?

From: Chuck Stringer
Date: Fri, 30 Sep 1994 13:17:22 -0500 (EST)

Peter Azlan writes:

>If I had the choice, (I'm still getting over the shock of having to repalce the silencers),
>I would definately go for the Mk2, for the reasons stated above.

I'm going with the MK1 mainly for financial reasons. British Only is selling them for $125US. Too reasonable to pass up.

Chuck

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1.6 Problems.

Date: Wed, 5 Oct 94 10:45:16 PDT
From: Derek Hamlet

Now that I own a Norton, I of course have problems, not big ones but a touch frustrating. The bike is a stock 71 Commando except for the Boyer electronic ignition. It starts beautifully, idles at some ridiculously low rpm., has no knocks, pings or other disatrous sounds emanating from its internals. It also does not seem to leak oil, wonder of wonders. However, in 3rd and 4th gear it runs out of "go" at between 4500-5000 rpm.

I can't tell you speed because it has the wrong speedo drive and tells me I'm doing 90 when its more like 50 or 55. It accelerates well through first and second and takes off in 3rd. AT around 4500 -4800 rpm it just runs out of poop and sounds like its struggling. As a fairly non mechanical person I'd describe the sound like wanting more fuel and not getting it. My first thought was water in the gas. Threw in some alcohol and it zoomed up to 5500 rpm and then within 5 minutes started doing the same thing.

Checked the plugs-------------perfect.

I haven't checked the air filter, but, will do so. It doesn't look particularly dirty. I'm wondering about main jets. Don't know what size they are, but, wondered if they could be partially blocked or the wrong size.

What about the Boyer, is there anything about electronic igniitions in these things which would cause a situation like I describe.

Whatever the problem is, I know it is relatively minor. I could ride the bike as a commuter for months, keep up to traffic and not even know I have a problem. However, I like to ride these things and that means twisties with an engine that responds.

Any ideas and advice will be greatly appreciated. Perhaps his eminence Mr. Kula who lives in my home town will grace me with a visit and

he can:

1. Take the bike for a run.

2. Offer advice and maybe even some guided wrenching.

Thanks folks.

Derek Hamlet

Date: Wed, 5 Oct 94 11:38:40 PDT
From: John Kula <JAKULA@bcsc02.gov.bc.ca>

Your problem is a classic: all the symptoms point to your jets being too small. When I was fettling in my Black Beast (the one that went to Hong Kong), I increased jet sizes progressively from 240s all the way to 285s. These latter were _still_ too small to have a ggod blast through the Hat, and I was going to move up to 300s, when the Strine bought it from under me.

Bigger jets. Colin has lots :-)

John Kula jakula@bcsc02.gov.bc.ca

Commando 930 (MacBeth)

Date: Fri, 7 Oct 94 08:14:48 BST
From: Peter Azlan

Two words to Derek Hamlet - 'Air Filter'.

Assuming this is the car type, round filter in a perforated metal band, between two plates, rear one fixes to Battery Tray, front one with holes for carb gaters.

I would say, the oil vent from the oil tank has spewed some oil onto the filter, did you top up the oil when the engine was cold ? Do the words, 'dry sump' and 'wet sumping' mean anything ?

Of course, even if the filter arrangement is not as described, and it's not a problem with the oil vent and 'wet sumping' it sounds remarkably like a clogged air filter.

Regards, Captain Norton.

Date: Sun, 6 Nov 94 20:57:01 PST
From: Derek Hamlet

And begone they were. Saturday dawned overcast and very fresh. Fired up the Nort and headed out to the BMW club breakfast. Given that I was probably faced with a day of frustration I figured coffee and toast with the retentive set would steel me for a frustrating day.

The bike was still behaving in a fitful manner, cutting out or rather failing to accelerate beyond 4500 rpm. Arrived at Colin's place. John Kula was already there hoping to get Colin working on this 930 Mcbeath. No such luck. Colin was replacing the throttle cables on a Bonneville for a transient guy on a trip. Hung around for two hours assessing the possibilities that I would get any attention. Decided to hang in. Kula dons my helmet and takes my Norton for a spin. Comes back with a host of possible problems that it could be. We won't go into them here. Suffice to say I'm sure glad it was none of those things.

At 1 pm Colin announces, "let's find out what's wrong with that thing" I smile, John looks a little crestfallen, but, he's a friend. First we pulled the coils. They tested out fine statically, but, who knows under load. Colin goes through junk box and we load on two 6 volt coils. One doesn't work. Replace it with a new one. Fire it up. Runs fine, but, you could still make it cut out with a quick roll of the throttle.

Hmmmmm. Not coils. Put a timing light on the left lead. Repeat procedure. Still cut out, but, timing light remains bright all the way through. Not electrical. Jeez, maybe it's carburration. Pull of top and bottom of carbs. Floats look good, no junk in the bowls.Rats, I had thought maybe that was it. Needles look okay, but, the taper is slightly different over the length of the needles. Colin says no problem as the taper over the last 1 1/2 inches appears uniform. Whip out the jets. Everything is stamped correctly.

Stare at jet holders. Stare some more. Look okay to me. Colin suggests that they don't look quite right to him. Right height, right threads, but, not quite like a Norton should have. He thinks some previous smart turkey swappped some parts around. Another rummage around. In go a different set of jet holders. Whip it together. On with the Belstaff, helmet and gloves. Fire it up and take off.

Oh joy. The little yellow bastard pulls like a tractor and just keeps on going. Lots of power, good acceleration and enough speed that I run out of road at around 85 mph. I'm grinning from ear to ear by this time. I can finally go for a real ride. I still think the carbs need a little fiddling. It's probably jets or needles, but, I think there's a little more left at the top end. However, that can await another day.

Many thanks to all of your and you many suggestions on trouble shooting this little problem.

As far as I know no bolts or other extraneous materials disappeared into vital part of the engine although one needle circlip did mysteriously disappear.

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1.7 Courtune.

Date: Wed, 05 Oct 1994 14:47:08 -0500 (EST)
From: Pete Serrino

Last night my friend Bobby Karras stopped by with his newly restored '68 P-11 Ranger. Its a beauty with its newly powder coated frame, candy apple red tank, and shiny new chrome. Bob wanted me to setup the carbs on his new motor and while I am no expert, the carb stixs and Colortune (tm) help a lot. The Atlas motor had been warmed up with Commando (9:1) pistons and a Leo Goff (LGR) cam. The carbs were new 30mm Amal MKIs (ticklers) which had been resleeved by Phil Radford (Fair Spares America) before they were ever used. Let me tell you they were a revelation on how an Amal can work. The mixture screws actually had some effect and the sweet spot could be pin pointed within a sixteenth of a turn and correlated with the Colortune. Idle was consistent between cool and warm. Thottle response was crisp even with the fresh motor.

Still too early too tell what the final settings will be. Anyone considering what to do with those worn concentrics; just get them resleeved and rejetted. They can work. If they don't fix the problem something else is wrong.

Cheers,

Pete

Date: Thu, 6 Oct 94 09:38:41 PDT
From: "Robert D. Burget"

Pete wrote:

>Bob wanted me to setup the carbs on his new motor
>and while I am no expert, the carb stixs and Colortune (tm) help a lot.
>The Atlas motor had been warmed up with Commando (9:1) pistons and a Leo Goff (LGR)
>cam. ....

What's a Colortune and how does it work?

Bob Burget, rdb@strata.com

Date: Thu, 06 Oct 1994 13:28:21 -0400
From: Pete Serrino

>What's a Colortune and how does it work?
>

Colortune is basically a replacement sparkplug with a glass/quartz window to the combustion chamber. Gasoline and O2 burn much the same as Acetylene and O2. Too rich produces an orange flame and too lean a blue/white flame. I find it makes things easier especially if your motor is no longer stock or for diagnostic purposes. I can't always tell if poor running is the result of a too rich or too lean condition. About $32. I don't have an address handy though.

Pete

Date: Sat, 8 Oct 1994 12:19:02 -0700 (PDT)
From: Nancy J Caputo

Pete writes:

>Colortune is basically a replacement sparkplug with a glass/quartz window to the
>combustion chamber. Gasoline and O2 burn much the same as Acetylene and O2.
>Too rich produces an orange flame and too lean a blue/white flame.

In my experience this device works OK at idle but then becomes unstable (and is hard to read) at higher throttle settings. Pete suggests it may be good for setting up a non-stock motor, but for regular tuneups I think it has limited usefulness.

Cheers,

Lou TM LUIGI ncaputo@uclink.berkeley.edu

From: Ralph Merwin
Date: Sat, 8 Oct 94 14:05:32 PDT

Nancy J Caputo writes:

>In my experience this device works OK at idle but then becomes unstable
>(and is hard to read) at higher throttle settings. Pete suggests it may be good
>for setting up a non-stock motor, but for regular tuneups I think it has limited usefulness.

The Colortune instructions mention something about not going above 3000rpm (or thereabouts - ti's been a while since I've been able to find mine). Way back when I ahd several brit-mobiles abd the Colortune and a UniSyn were essential for tuning...

Ralph

Date: Wed, 12 Oct 1994 16:20:28 -0700 (PDT)
From: Nancy J Caputo

Ralph is correct-- the manual for the Colortune specifies 3,000-4,000 as a max rev for testing. Hmmm, at those revs I think my Nort would walk away from me while I was trying to read the color.

I should add that reading the device may be more difficult if you have an Interstate tank because there's not much room for viewing. Roadster owners may have a clearer shot at the plug tip.

Cheers,

Lou TM LUIGI ncaputo@uclink.berkeley.edu

Return to the Contents Page

1.8 Fuel.

Date: Fri, 28 Oct 94 15:24:26 EST
From: Nigel Nicholson

Gents; I've thought of more new and challenging questions for Trident experts :)

Can anyone tell me the best fuel to use in a 73 Trident? The owners manual says 97 octane minimum. The Shell garage manager near my home says that number was based on the old UK octane rating system and that the US rated 93/94 octane fuels today are good enough.

Does unleaded fuel damage our valves?

What is the current thinking on synthetic oils verses non-synthetic?

Are any of the 73 manual recommended specifications (fuel, oil, plugs, et al.) overcome by events? That is, are better choices now available?

BTW, I've been looking into the question of resleeving carbs. This is an interim report: People on Brit_Iron have quoted me various prices between $80 per cyclinder to $40 per cylinder, depending on where and when they had the work done.

One local Triumph specialist shop I called said they didn't do such routine maintenance work on Triumphs but could save me a lot of money by replacing the Amals with new carbs.

They said the $195 approx cost per carb for new was considerably less than the cost of resleeving. Thank God for Brit-Iron, eh?

Nigel Nicholson

From: Graeme Harrison
Date: Fri, 28 Oct 94 14:31:04 PDT

>They said the $195 approx cost per carb for new was considerably less
>than the cost of resleeving. Thank God for Brit-Iron, eh?
>Nigel Nicholson

I'll say...imagine if they tried to sell you 3 new carbs with a 1995 Trident attached to them for $7995! :^)

Date: Thu, 30 Jun 94 13:19:41 CDT
From: Chuck Kichline

When I dragged my '68 Lightning out of the garage (1985-90) I was plagued with rich running - especially at 45-65 mph; missing out, black plugs, the works! I thought it would be a leaky float or a sticky float needle, since the bike had always been spot on before.

After much frustration, Steve Tuffs steered me into needle jets and needles a step leaner than stock and the "new style" (whatever that was). That solved the problem. Steve mentioned that the gas had changed and theflow properties were different. I could believe that. But if so, then

wouldn't all the old published specs be incorrect?

Anybody with a view on fuels and jetting willing to share some opinions?

Date: Thu, 30 Jun 94 14:41:33 CDT
From: Chuck Kichline

>Regarding the gasoline question, I remember reading in Vintage Bike that all
>Triumphs should run on at least 93 octane (even though my workshop
>manual specifies 91 as the minimum), which can be a bit hard to find these days, at least in
>Canada. I buy the highest I can find easily here, which is 92 octane, and put in a tablespoon of
>octane booster with each tank fill.

Didn't the octane ratings change in the mid 70's (down in rating by 2 or 3 points)? I understood that it was the testing method (something about Research Octane Number) that changed and not the actual fuel. If so, we shouldn't need the unobtanium fuel. Gotta be a Petroleum Engineer out there somewhere!

Date: Thu, 30 Jun 94 21:37:52 BST
From: Latte' Jed

>Didn't the octane ratings change in the mid 70's (down in rating by 2 or 3 points)?
>I understood that it was the testing method (something about Research Octane Number)
>that changed and not the actual fuel. If so, we shouldn't need the unobtanium fuel.
>
>Gotta be a Petroleum Engineer out there somewhere!
>
>Regarding the gasoline question, I remember reading in Vintage Bike that all Triumphs
>should run on at least 93 octane (even though my workshop manual specifies 91 as the
>minimum), which can be a bit hard to find these days, at least in Canada. I buy the highest
>I can find easily here, which is 92 octane, and put in a tablespoon of octane booster with
>each tank fill.

The octane rating did go down, leaded fuel was higher octane than regular unleaded. When I first got my Trident (first Brit-Bike, can't believe I got another one after that intro) I was horrified to find it wanted 98 octane leaded. Turns out a British octane is different than an american octane, I think the british use Whitworth octanes. I run most of my bikes on 89, every now and then I toss in some 92 or 93 when it's convenient. No problems.

Date: Fri, 01 Jul 1994 07:26:33 -0500 (EST)
From: Pete Serrino <SERRINOP@ehsct7.envmed.rochester.edu>

Chuck writes:

>After much frustration, Steve Tuffs steered me into needle jets and needles a step leaner
>than stock and the "new style" (whatever that was).

This past year a member of our Norton club (NY Norton owners) had his carbs resleeved and replaced the needles and needle jets. The needles he received were shorter than his originals. After repeated fouling he finally discovered he was sent "Triumph" needles. I assume these are the "old" style for Triumph owners. When he replaced them with the original longer style everthing cleared up. BTW he said the bike ran like a bat out of hell for about three miles before loading up and stalling out with the short needles.

>Anybody with a view on fuels and jetting willing to share some opinions?

I am convinced the newer fuels burn richer than the gasoline sold when our bikes were new. It seems my Norton is more sensitive to this than my other bikes though. It also varies quite a bit by region. A few years ago at the Norton National at Laconia, New Hampshire most everyone was complaining of fouled plugs. (<1000 foot elevation). Most of us had ridden in and had no problems until after gassing up there. Things cleared up on the way home after a couple of tank fulls.

Pete Serrino

Return to the Contents Page

1.9 Carb Configurations.

Date: Wed, 25 Jan 95 14:48:24 GMT
From: Peter Azlan

Firstly, the more I think about the humble Amal Mk1 the simpler it gets in my mind. You know the stuff, when your new to anything its Complicated, there's soo much to take in, the picture of it in your mnd is enorm. Theres soo much to remember and all that. But hey, we are talking 1960, cheap pot metal carb here, not the engine room of the QE2.

So what you may ask, what revelation has suddenly popped into your head. Well, it occurrs to me, I'm sure i'm not the first, infact I am begining to think there's no thought anyone can have anymore that wasn't someone elses first, that the biggest problems owners of Amal graced motorcycles must have with there idle is wear between the throttle slide and body.

If you think about it, and I have, there is the idle circuit, and as long as it is clear of crap, the only other source of air is arround the throttle slide. So, if you have a bad idle, check the Air Filter, check the inlet manifold, check the adjuster screws for the little rubber sealing rings, but most of all check for wear in the throttle slides. you know, it also occurs to me that the design is actually quite poor. There should be a better way of sealing the throttle slide, (pot metal) to the carb body, (pot metal) to form an Air tight fit. Did someone at the back say Lunds ?

Enough ranting and back to the Crankshaft:

John Pinkham, don't pannic, don't tear down that engine. I've had the same thing on my bike for at least 20K miles and nothings happened since. I assume some of the play is comming from the superblends, and I think there is a shim or two in there but excessive, (read beyond the limits in the manual) does not mean the thing is about to blow up or has been eating itself to bits. Its at this point I would like to suggest a regular inspection of the magnetic drain plug in the bottom of the crankcase, dont worry, theres bound to be _some_ bits of metal floating around, thats what the magnets for.

Back to the Carbs, Please send in config and setup stuff. Its also useful if you include any Airbox or Exaust modifications, and any problems you are currently experencing.

Regards Captain Norton.

Date: Sun, 2 Oct 1994 20:05:10 -0700 (PDT)
From: Nancy J Caputo

Better late than never:

Cheers,
Lou TM LUIGI Deerslayer

Date: Mon, 3 Oct 1994 12:08:35 +0800
From: Jamie Hamilton

Only complaint about MkIIs is that you cant get one of those funky Unipod air filters to fit over 0the mouth. They probably do make a larger size but then frame gets in the way (carbs point straight back not slightly to sides as I have noticed on some models). Ugly plastic airfilter box set up is my only gripe about a truly beautiful motorcycle. She idles nicely at about 800 with just the occaisional hic on right hand side (try to eradicate it from time to time - end up saying after 30 mins fiddling f*@k it lets go riding). Left hand side keaps time like Charlie Watts.

Jamie

Date: Mon, 3 Oct 94 09:03:49 BST
From: Peter Azlan

Nancy, firstly thanks for posting this stuff. I for one find it really interesting looking at other Commando carb setup information, and I feel it gets us all 'one step closer' to sorting out a lot of carb problems. It's unfortunate, therefore that yours is still only the third set of Amal information posted since my request, ah well. Whats supprising is the number of 850's with Sectioned Spray tubes out there, I thought it was kinda special.

Further to your post, could you include the Engine No and date of manufacture, this information is stamped on the metal plate fixed to the headstock behind the headlamp. I am also particularly interested in the Throttle Number, (probably a 3 or 3 1/2), its stamped on the top of the throttle slides. And also, what is a 'contis' ?? Please let us know if the bikes running ok, and if not any problems you feel may be related to the carbs, poor idle, fowled plugs etc.

Thanks in advance, and a gentle reminder to all other Commando owners on the list to post the same information for the benifit of us all.

Date: 3 Oct 1994 09:04:51 U
From: Eric Rogge

My Norton's specs

As per Captain Norton's request:

Runs great, hot idles like s***. I'm considering slides one size down/up, but I guess that means that I'll have to get them resleeved too.

Cheers

Eric Rogge

Date: Tue, 4 Oct 1994 17:14:27 -0700 (PDT)
From: Nancy J Caputo

>Further to your post, could you include the Engine No and date of manufacture,

Engine 302540, manufacture date somewhere between 4-6/73. 3 1/2 slides Conti mufflers. Tried reverse cone and seemed about the same as far as correct tune goes.

The significant difference for my carbs was the .105 jets post resleeve. Prior to the resleeve I had been running .106 with the needle in the top groove. It ran very rich after resleeving, and I tried N8Y plugs which seemed to prevent loading up around town. But it still wasn't good enough and the .105s made the difference. Seems there are a lot of folks who face this problem once they install their redone carbs.

Cheers,

Lou TM LUIGI Deerslayer

Date: Wed, 25 Jan 95 14:47:46 GMT
From: Peter Azlan

Further to my last post on Amals on Commandos, I would like to add:

To Start with, this is how it came from the factory:

Commando 850 Mk2a Manufactured April 1974 originally as a High Rider Engine/Frame number 31(something).

Now, if you have a Commando, please post your Amal Carb configuration/Settings. Provide the same info as above or use this mail as a template. I would really like to find out what other people are running.

Also, we could start the same thing for Triumphs.

Owners of Minuki do not need to apply.

P.S. I'm sure the needle position starts at 1, (top) with 3 the (bottom). although we usually say Raise or Drop the needle a notch and dont refer to position. If the needle goes up, more petrol goes in (Ritcher) if the needle goes down, less petrol goes in (leaner). Oh, raising and lowering is relative to the throttle slide, thus if its in pos 2, (middle) position 1 (top) lowers the needle and reduces the petrol content of the mixture.

Regards, Captain Norton.

Date: Wed, 25 Jan 95 14:48:08 GMT
From: Peter Azlan

So far we have 3 responces to the request for Amal configurations/setups, and one of thoes is mine. I thought the number stamped on the carbs would be the same on both carbs, I'll now have to go out the garage and check.

The preliminary results are: Commandos run better with a throttle slide one size smaller than originally fitted. Could this be the result of modern fuels ?

Note on 4 id ring needles: As far as I know, the 4 id ring needle is only used with the sectioned spray tube.

And someone asked, what's a spray tube ?

Well... If we start with the throttle slide, the large cylinderical bit the throttle cable is attached to, the bit that goes up and down when you twist the throttle on the handlebar. The needle is fixed to the throttle slide, on amal Mk1 carbs, the needle is held with a brass clip which fits into one of three groves in the needle. The clip is held against the throttle slide by the throttle slide return spring. When assembled, the needle goes into the base of the carb, into the needle jet. If you look down into the carb when the top is off and view the top of the needle jet you will see a brass thing poking up into the carb body arround the needle jet, this is the spray tube.

A brass tube which rases the level at which the fuel enters the airstreem. The spray tube can be removed by carefully tapping the thing out from above, after removing the needle and main jet and the jet holder. Once removed, the spray tube is the shape of a top hat with no top to the hat, the bottom being a kherled section which provides an interferance fit which holds it in place, the sides being the tube. A sectioned Spray tube is a tube where one half of the tube which projects into the airstreem has been removed. A sectioned spray tube is installed with the cut away positioned towards the engine.

Note on idle jets: The Mk1 Amal has provision for an idle jet, only one should not be fitted. It locates on the underside of the carb body, its purpose is to restrict, (govern) the amount of fuel passing into the idle mixture curcuit. The idle curcuit takes in air from a small hole bellow the main air intake, there are actually two holes but one is blanked off. The blanked off hole leads to a drilled hole inside the carb, above the float chamber, which takes the idle jet. As far as I remember, the air component of the idle circuit is the one which is regulated with the idle mixture screw on the outside of the carb body. Both components enter the airstreem through two tiny holes after the main jet and spray tubes. You really need to look at a carb body for all of this to become clear. Additional note: the thredded hole which takes the idle jet also appears as a sleved hole on some carbs I have seen.

And now, back to the point: I believe such idle jets are only used for two stroke applications with the Amal Mk 1.

Clutches: My Commando was originally fitted with fiber plates, they worked fine but I changed to Bronze, well it was the thing to do at the time. This also worked fine for a long time but I then had a lot of problems with both slip and drag. After a lot of mucking about I changed the plates to sureflex, (you need to add a plain plate when you do) and replaced the clutch center, the bronze ones can make an impresion on the inconsistant hardening on the centre, which stop the plates from freeing causing drag. The only trade off here is wear, the bronze ones dont appear to wear at all, where as the sureflex ones probably will.

Also a note to John P on the belt conversion. One of the most significent reasons for converting must be it allows the clutch to run 'dry'. Just remember to fit the sealed clutch bearing.

Regards, Captain Norton.

Someone also asked, how do I tell if my carb slides are worn ?

Well the answer is, when you canít get the bike to idle.

Now, who said the MK2 Amals were made of aluminium with coated Slides, and what about the differences between Triumph and Norton riders ??

Regards, Captain Norton.

Return to the Contents Page

1.10 Float Height.

Date: Tue, 5 Jul 94 10:36:17 EDT
From: John Pinkham

>Actually, I've always wondered about about the official specs for the float bowl
>setting since I've been unable to find them anywhere, so please send the data
>from the technical bulletin. Thanks.

The following is a repeat of an earlier post on Amal concentric float level.

Triumph Service Bulletin dated 7/18/73

Checking and adjusting the Amal Concentric Float Level.

"Occasionally you may encounter a machine which runs erratically due to an over-rich condition. You may also find that this problem machine is fitted with the proper size jets and has the same adjustments as a model which runs perfectly.

After many hours of investigation, we found that the normal cause for the problem outlined above is a high float level setting.

Check Float Level:

Remove the float assembly from carburetor. Drain gas from float bowl. Using a small screwdriver or other suitable tool, depress the float tab which operates the float needle, until the needle contacts seat. While holding the float in this position, measure the distance from the top of the float bowl to the top of float. The proper measurement is .080 [Norton: 1/32-1/16]. If the measurement is less than .080 the float level will need lowering. See Figure 1. [Shows the measurement taken at float end opposite the needle end. Note the float top is *below* the float bowl top.]

Adjusting Float Level:

Remove all fittings from float bowl. Using a propane torch, heat the bowl slightly. This will free the brass seat so it can be easily moved. Using an 1/8 " diameter rod, gently tap the brass seat until the proper setting is attained. See Figure 2. [Shows the float bowl inverted and the drive rod vertical resting on the bottom of the brass seat.]

CAUTION: Do not attempt to move seat without heating bowl.

Note: The .080 measurement is proper for current Single, Twin, and Triple models.[Triumph]

Phil Radford of Fair Spares, San Jose provided this bulletin. He said that he puts his thumbs on the ends of the hinge pin and then inverts the bowl to check the distance. This way it is easier to see when the needle is about to contact the seat. Helps to have an extra hand or two!

From: MikeTnyc@aol.com
Date: Wed, 06 Jul 94 00:44:13 EDT

>Using a small screwdriver or other suitable tool, depress the float tab which operates
>the float needle, until the needle contacts seat. While holding the float in this position,
>measure the distance from the top of the float bowl to the top of float.
>The proper measurement is .080 [Norton: 1/32-1/16]
>
>Phil Radford of Fair Spares . . . said that he puts his thumbs on the ends of the hinge pin
>and then inverts the bowl to check the distance.

I can speak from experience on this subject, having spent half a season trying to get the damn float levels right on my bike: the Amal brochure quoted above is [unintentionally] misleading, and you may get disastrous results doing it the way they say. Phil Radford's method, however, is just fine. The difference is that nowadays [though not when Amal wrote those instructions] the PIVOTS in the typical Concentric float are significantly WORN. If you push down on the float tab to measure the float height, the play in the pivots does not get taken up, and when the float is later raised by the gasoline, that play can leave it as much as 1/16" higher than your adjustments intended.

To compensate for this play, raise the float with your finger until the needle hits the seat, or [as Phil does it] turn the bowl upside down and let gravity do it.

The problem with raising the float instead of pushing down the tab [or with turning it upside-down] is that the hinge pin doesn't stay in its groove. Some authorities suggest peening the groove in the bowl to keep the pin in place. I epoxied it instead, which seemed a bit more undoable if I need to undo it someday. Getting the float level right without holding the pin down somehow is very difficult, and the pin may keep on moving around while the carb is in use, thwarting your adjustment. (By the way, the INOA Tech Digest recommends 3/32" for a Norton, which is what I used. I don't see why this would change by brand of bike).

All in all, a little on the low side is probably better than too high, and the different specs might exist because some incorporate "safety factors." If the float is a little low, the tickler will not operate as quickly (or perhaps at all), and the bowl might possibly "run out of gas" under extreme throttle conditions. If the level is too high, however, you get extreme richness with no apparent cause, and vibration can even make gasoline splash out of the tickler-holes at idle. If the float level height is within these limits, however, I don't see how some variation would significantly affect the mixture.

From: John Pinkham
Date: Tue, 12 Jul 94 11:21:28 EDT

Regarding the correct float level for Amal concentric carbs for Norton Commandos: The Norton Tech Digest says to have the float top 3/32 inch *ABOVE* the float bowl top. According to the Triumph service bulletin and Phil Radford of Fair Spares (USA) this is WRONG. The float top should be *BELOW* the top of the float bowl casting [Minimum 0.080 inch for Triumphs and 1/32 -1/16 inch for Commandos]

When asked about the error in the Tech Digest, Phil said "Remember, it was written by laymen".

Return to the Contents Page

1.11 Flat Spots.

Date: Fri, 19 May 1995 09:03:10 +0100 (BST)

From: Peter Aslan <paslan@uk.mdis.com>

I while ago, after replacing the carbs on the ol' Commando I started suffering from a definate flat spot in accelaration, particularly apparent after slowing down. You sort of crack open the throttle, and the bike thretens to throw you over the handlebars, before kicking you in the bum. It was, to say the least, a little disconcerting.

Now the Amal Mk1 Carbies were all set up, sectoned spray tubes an all, just like the carbs they replaced.

I puzzled over this for some time and even wrote to John Hudson, then Technical Advisor for heavyweights in the Norton Owners Club.

The reason for this problem slowly became clear, and now seams so elementary. Firstly, these non 'CV' type carbs are prone to this problem, the amount of fuel and air supplied to the engine is in proportion to the rotation of the right hand, rather than the speed and therefore need of the engine. This is something Amal try and deal with by ensuring a pool of petrol is kept at the base of the carb, by the spray tube.

Anyhow, the thing we are really interesting in here is the transition between the Idle circuit, (Throttle Closed), and the throttle slide cutout, Needle and Jet Circuit, (throttle 1/4 Open). If the Idle circuit is too lean, then you will get this 'flat' spot in throttle responce.

All this is complicated considerably if the slides are worn, and/or if the mixture has been set with a Colourtune or using the traditional method, which sets it, IMHO, a bit too lean.

If your car bodies are in good shape, then it should be possible to sort this, as described.

If all else fails you might try moving to a throttle slide of a smaller number. These are usually 3 1/2 on the Commando, moving to a 3 increases the suck on the fuel, and richens the mixture on small throttle openings, Idle to 1/4. BTW, Throttle slide numbers correspond to 1/8ths of an inch between the base of the slide and the top of the cutout.

Also of note, we must ensure we do not have restrictions or obstructions in the lower part of the inlet tracts. This is discussed in detail in the latest copy of the INOA Norton News. The point is, if you canít get it to idle right, youíll never be able to set the idle mixture right to fix the flat spots.

Return to the Contents Page

1.12 Main Jets.

Date: Mon, 21 Aug 1995 10:12:34 -0400
From: Pete Serrino

Well, thanks to Bob Cram pointing out the problems with aftermarket jets I have just made a quantum leap in dialing in my 750 Commando. For the past year and a half I have been trying to get that last 1000 rpm in top gear. Couldn't make sense of the fact that I would put in "richer" jets and find my plugs looking leaner and ultimately burned an exhaust valve.

This weekend I got out my selection of Amal main jets and discovered I had an assortment of genuine and unmarked (except for size) jets.

Using a set of crude measuring devices (drill bits) I discovered the no-name 260s were actually smaller than the the genuine 240s. One genuine 280 was .004" (about 4 jet sizes) different from a no-name one. That realized I set out to determine the actual jet needed by the traditional plug chop route. 240s and 260s showed about the same results ie. white ceramic with a clean almost blue ground electrode (way too lean) and top rpm ~6,400. I discovered my "250s" had been drilled out and were actually about 290s. I passed on the 280s because of the mismatch and I had no idea what size they should be. At the first opportuninity with the now modified "250s" the bike pulled right on to 6,900 (20 tooth CS sprocket) with a lot more on tap. The plugs showed just the slightest bit of tan but the electrode was still clean and carbon free. It also looked like I may have still had one or two black specks on the ceramic. Still a bit lean but now it pulls.

When I ordered some new 300 mains from my local dealer (BBC) and told Jim about the problems with the aftermarket jets (both main and needle jets) he told me he was aware of the problem and was only dealing with the genuine articles.

All this prompts a couple of questions. First off does anyone have a conversion table for Amal jet sizes vs. actual dimension. A 240 main measures .052" +/- .001" or ~1.32mm. The 240 must refer to some sort of flow rate and not to the dimension as do Bings or Dellortos. Judging by the disparity in the jets I think I could do better drilling out a pair to suit.

Better yet if anyone knows of a source for micro-broaches I would appreciate it.

The second question is why such rich jetting is required. The motor is similar to a Combat in specification: 10:1CR, 32mm MKII carbs w. K&Ns, stock roadster pipes with peashooters, megacycle 560-00 cam. Cam lift is .396" intake and exhaust. I am not sure how the duration compares. The head has been gas flowed (30 mm intake tract) but the valves are stock.

The original Combat was spec'd at 230 mains vs 220 for the standard motor. I can only speculate the current stuff they call gasoline is quite a bit different than suspected or Leo Goff did one hell of a flow job.

BTW I have a friend who will be checking all of the jets on an optical comparater so we will have a better idea of the tolerances.

Cheers,

Pete Serrino

'71 Fastback

Date: Tue, 22 Aug 1995 09:07:19 -0400
From: Pete Serrino

Last evening my friend dropped off a handful of Amal Concentric/MKII main jets which had been all measured up. I was a little disappointed but not surprised at the results. These things have stymied my tuning efforts for some time now and now I know why.

For the record they were measured on an Optical Gauging comparator by the chief inspector at the company where the comparators are built. It is capable of at least 5 decimal place accuracy but only four were given (close enough). Those listed as Amal have the name stamped on them, the no-name ones are listed as nn. Units are inches and refer to the diameter. Divide by .03937 to get millimeters.
 

    • Amal 230 .0529
    • Amal 230 .0530
    • Amal 240 .0512
    • Amal 240 .0519
    • Amal 260 .0531
    • nn 260     .0535
    • Amal 280 .0555
    • nn 280     .0576
I was able to double check the 230 and 240 jets thinking they might have been mislabled. A #55 drill bit (nominal .052") actual .0518" would pass through both 230s easily but not through one of the 240s. The other 240 was extremely tight. Also note the 260s were virtually the same size as the 230s which explain the continued leanness with 3 size over jets.

I located a copy of "MODERN MOTORCYCLE MAINTENANCE" by Bernal Osborne, 1961 printing. He lists some data for Amal main jet sizes. The Amal sizes do refer to gasoline flow in CCs per minute:

  • Amal 180 .045"
  • Amal 200 .048"
  • Amal 220 .050"
  • Amal 240 .052"
  • Amal 260 .055"
  • Amal 280 .057"
  • Amal 300 .059"
The list stops at 300 but has a few listings down to Amal #20 mains.

Not many folks have access to a comparator to check these things. I understand Amal is running under new management. Hopefully the quality control will improve.

Cheers,

Pete Serrino

Date: Thu, 30 Jun 94 09:29:52
From: Bob Cram <cramb@herald.usask.ca>

I bought a 72 Bonneville a couple of years ago and have been slowly improving it. This past winter I rebuilt the carbs. When I took them apart I found the left carb had a 190 main jet and the right carb a 180. Upon checking the original factory parts manual I found it specified 190 main jets for the T120R Bonneville, so I put new 190s in both carbs.

Since then I have been having misfire problems from about one-quarter to one-half throttle, usually in the 2500 to 3500 rpm range, and it tends to be worse while accelerating. Plug readings show the bike is running rich. I have analyzed the bike to death and cannot find the cause of the problem. It is not the needles, which I assumed at first. I have them set at the weakest setting now, the top groove, which is also the factory specified setting. The problem does not appear to be electrical so far as I can determine, which leaves carburation.

Last night I noticed in the original workshop manual that it specifies 180 main jets for all dual carb 650s in 1972, i.e. a contradictionn with the parts manual which I followed in installing 190s. So I went to J.R. Peters' Bonnie: The Development History which has specs charts for all years and models of the Bonneville. His book says 180 for the T120 (UK model) and 190 for the T120R (US export model). Mine is a T120R, so the 190s I put in should be all right, except that Peters book contradicts the workshop manual. (Incidentally, the parts manual I have, which was presumably for North America, doesn't even mention the T120 just the T120R).

Does anyone have any idea what the proper main jet size is? Do you think this could be the cause of the overly rich mixture and misfire problems I'm having? Personally, I'm dubious that main jet size (especially such a small difference as 180 to 190) would affect mixture and misfire problems in the one-quarter to one-half throttle range, where the mixture is governed by the needle and not the main jet. However, since the needle seats into the jet, and a smaller jet size would mean less gas flow, maybe???? Anybody out there got any brilliant advice on this?

Date: Thu, 30 Jun 94 11:22:02 -0600
From: Andrew Wolf

Bob writes:

>Since then I have been having misfire problems from about one-quarter to
>one-half throttle, usually in the 2500 to 3500 rpm range, and it tends to be
>worse while accelerating. Plug readings show the bike is running rich.

I have rebuilt MANY anal carbs.

Rules:

1. They are all worn out

Usually I have my worn carbs bored out by Lunds

2. The needle JET is worn

You cannot imagine how many carbs have worn needle jets, its cheap and it is likely the cause of your rich running. I have often cheaply fixed the anals with NEW needle jets

3. Slide cutaway is WRONG

likely a 3 1/2 is the usual one.

Before you spend much replace the NEEDLE JETS, no you will NOT be able to determine if they are worn, however the improvement will be so noticeable that you will be Amazed.

Andrew Wolf

Date: Thu, 30 Jun 1994 10:56:00 -0700 (PDT)
From: Stephen Hill 356-9389

Bob Cram writes:

>Does anyone have any idea what the proper main jet size is?
>Do you think this could be the cause of the overly rich mixture
>and misfire problems I'm having? Personally, I'm dubious that
>main jet size (especially such a small difference as 180 to 190)
>would affect mixture and misfire problems in the one-quarter to
>one-half throttle range, where the mixture is governed by the needle
>and not the main jet. However, since the needle seats into the jet, and
>a smaller jet size would mean less gas flow, maybe???? Anybody out
>there got any brilliant advice on this?"

Somehow this questions has a familiar ring to it. Maybe it is one of those elemental questions, like why is there air?

Your experience sounds like mine, although I have noted that a misfire or lumpiness at closer to quarter throttle, and it tends to diminish if I am accelerating. What I found is that the idle mixture screw has an infuence up to about quarter to third throttle, despite all the good references that say it affects idle only. This may be a compromise setting which is trying to deal with wear in the slides. Good luck.

Date: Mon, 4 Jul 94 12:57:56
From: Bob Cram <cramb@herald.usask.ca>

My original question about whether switching my 72 Bonnie from 190 to 180 main jets would solve my misfire problem has sparked a lot of discussion. Anyway, I thought you'd like to know that I made the switch on the weekend and experienced a very noticeable improvement. The mixture is leaner now and plug readings are better. However, it still misfires a bit, but over a narrower throttle range and not as badly.

Although the books say main jets aren't supposed to have an influence until three-quarter throttle, it obviously made a difference in my case in the one-eighth to one-half throttle range. I presume that this is because all fuel goes through the main jet to get to the needle jet. Thus the quantity of fuel flow is directly affected by main jet size even at lower throttle openings. What the books should say is that the main jet size is the sole influence on fuel flow above three-quarter throttle, and below that it is a factor along with throttle cutaway, needle jet size, needle size, etc. Does that make sense?

Re the question that arose last week about different needle jets and needles in the more recent years, Triumph did make a change about 1969. I have more accurate information at home and will try to remember to bring it tomorrow. Essentially, though, the more modern needle jets had an extra very small cross-sectional horizontal hole through them giving better flow characteristics. Older Triumphs can be improved by using the newer system, or so the source I have claims. However, it is crucial not to mix parts, such as putting an old style needle with a new style needle jet. Anyway, I'll send the accurate details tomorrow. For those of you with copies, it is in Nicholson's "Modern Motorcycle Mechanics," a great out-of-print book for British bike fans, but hard to get hold of now.

Date: Tue, 5 Jul 1994 10:20:17 +0200 (METDST)
From: Rolf Clausen <ingringr@inet.uni-c.dk>

My 'box says that on July 4., Bob Cram wrote:

>My original question about whether switching my 72 Bonnie from 190 to 180 main
>jets would solve my misfire problem has sparked a lot of discussion. Anyway, I
>thought you'd like to know that I made the switch on the weekend and experienced
>a very noticeable improvement. The mixture is leaner now and plug readings are better.
>However, it still misfires a bit, but over a narrower throttle range and not as badly.
>
>Although the books say main jets aren't supposed to have an influence until three-quarter
>throttle, it obviously made a difference in my case in the one-eighth to one-half throttle
>range. I presume that this is because all fuelgoes through the main jet to get to the needle jet.
>Thus the quantity of fuel flow is directly affected by main jet size even at lower throttle
>openings. What the books should say is that the main jet size is the sole influence on fuel flow
>above three-quarter throttle, and below that it is a factor along with throttle cutaway, needle jet
>size, needle size, etc. Does that make sense?

Ahem, may I express my h.o.? Thank you..

From my technical viewpoint there are some truth in your words, but only some. The fuel will be restricted and hence metered by the part of the carb that provides the biggest resistance. As the main jet can deliver enough fuel for full throttle riding, it will not restrict fuel very much at smaller throttle openings. But this would depend on all other things being equal, which they aren't - ie. needle position in jet not constant to take one example. Pressures around needle being different in different running modes etc.

So much for theory (and it has been some time since I studied these things, so the reasoning may be a bit blurry).

My practical experience says that the original wording is not far from truth. Reducing main jet size should lead to other problems at higher speeds, lean and hot running. How does the Triumph perform after the change?

I'd suspect you'd have expended some go, and would think of looking for another reason for the misfire.

PS. Does my '37 Matchless mod. X run. Yup. Trouble free? No. Big misfire the other day, lost one cylinder 80 percent, nearly didn't make it home. Head scratching. Think think. Notice lots of sparks at one set of points, no sparks at the other. (Two sets because of homemade ignition, superior to magneto in all respects). More think. Buy new condensers. Take old ones off, find wire broken from vibration. Weld old wire to old condenser. Good as new. Now have extra condensers!

Date: Tue, 5 Jul 94 09:13:30
From: Bob Cram

Rolf Clausen writes, in part:

>The fuel will be restricted and hence metered by the part of the carb that provides
>the biggest resistance. As the main jet can deliver enough fuel for full throttle
>riding, it will not restrict fuel very much at smaller throttle openings. . . .
>Reducing main jet size should lead to other problems at higher speeds, lean
>and hot running. How does the Triumph perform after the change?

I agree, in theory, but as so often happens theory and reality don't seem to match. A real Amal expert could probably figure this one out, and maybe someone will do that for us. One piece of information in my original message about this is that different Triumph factory sources gave different specs for this year for the Bonneville. Some said 190 for the main jet; some said some 180; some listed both.

Date: Tue, 5 Jul 94 10:50:34
From: Bob Cram

Thanks Rolf:

The 190 main jets I was using were brand new. The 180s, which I got from a friend, were used, hard to say how used, but I gave them a good cleaning. The difference may be small, but it was visible to the naked eye that the used 180s were still smaller than the new 190s. Interestingly, when I took out the old jets this past winter, I found that the previous owner had a 180 in the right carb and a 190 in the left carb. The left carb is only a couple of years old. The right one is older, probably original, but has all new internals. It wasn't rebored, but there seems to be a tight fit between it and the throttle slide.

Yes, I do have air filters, and they are both brand new. Believe me, I've been puzzling over this for awhile and trying everything. The suggestion I got from John Pinkham regarding the Triumph Service Bulletin of 1973 and float levels looks very promising.

Date: Tue, 5 Jul 1994 17:28:11 +0200 (METDST)
From: Rolf Clausen

Just a small snip from Bob Cram's writings:

>One piece of information in my original message about this is that different
>Triumph factory sources gave different specs for this year for the Bonneville.
>Some said 190 for the main jet; some said some 180; some listed both.

I'd say there shouldn't be such a big difference between a 180 and a 190 jet. In my experience the *correct* jet is a compromise, and sometimes the smaller jet would be better than the other or just the opposite. A worn 180 could be a 191 or maybe even 195 if the fuel contains a lot of grindy stuff.

If your air filter is dirty this can outshadow such a small difference in jet sizes. You do have an air filter, don't you?

Rolf,

from small place Denmark (which is not the capital of Finland!)

From: Mark Stephens
Date: Mon, 23 Jan 1995 15:39:24 +0000 (GMT)

Hi,

I thought I would try and sort out a problem with my T140D over the next month or so. The basic problem is that the motor misses badly when you give it full throttle. It seems particularly bad around 4000 r.p.m plus.

I ought to say this isn't done very often as the cost of replacement indicators, lights etc makes it a bit expensive and I've had the bike for 8 years and want it to last at least another 8!

Here are some of my thougts about the problem. Any opinions would be very much appreciated.

1. I ride it too slowly (lots of town riding), hence it cokes up and needs to be given a bit of a caning more often!

OR 2. It has non-standard pipes (much less restrictive than the original 2 into 1 set-up) so the mixture is all wrong. I have up jetted from the original 190's (I think) to 210's to try and compensate. Needle positions have not been changed. OR 3. The coils are on the blink.

My feeling is that it is probably a combination of 1 and 2? Any advice anyone?? BTW The valves and guides are new and the colour of the plugs looks fair.

Also the bike seems a bit flat at the top end. Is this just the way that later Triumphs behave and if so is there a straightforward way to give it a bit more go?

Thanks in anticipation.

Date: Mon, 23 Jan 95 13:17:14 +0000
From: Bob Cram

Mark Stephens writes:

>I thought I would try and sort out a problem with my T140D over the next month
>or so. The basic problem is that the motor misses badly when you give it full
>throttle. It seems particularly bad around 4000 r.p.m plus.

If it happens only at full throttle, then my guess is that it is a main jet problem, perhaps too rich because of the 210s you put in. This is because the main jet controls fuel/air mixture from 3/4 to full throttle. An electrical problem would normally be constant across all throttle openings. Also, if you decoked the head when you did the valves and guides, carbon shouldn't be a problem. Once again, I would expect carbon to affect running at more than just full throttle.

To check this out, ride the bike out to a stretch of highway somewhere with a spot you can comfortably pull over on, thoroughly warming it up on the way there. Take along a new set of plugs and a plug wrench.

Put in the new set of plugs (properly gapped of course), start it and take it up quickly to full throttle in top gear (watch out for radar). Once you have been cruising at full throttle for 15 or so seconds, pull in the clutch and hit the kill switch (in that order please). Pull over and do a plug reading. This is the only way I know of to get a true plug reading based on the effect of the main jet. Most of our daily riding is only up to about 2/3's throttle, so just pulling the plugs after a normal ride doesn't give you a reading of the main jet mixture. And if you use the plugs that are in it now, their colour will already be affected by all that daily riding.

This part may be obvious, but if it's too rich (black, carbon deposits) try a main jet one size smaller, and see how that works. If it's too lean (usually white or close to white), try a main jet one size larger. If the it's correct (light brown or gray), then I've just wasted your time and this didn't work because the fuel/air mixture is not the problem.

Trouble with this system is that it is trial and error until you get it right, which means trying several main jets and new plugs if you don't get it right after the first plug reading. Luckily main jets and plugs are fairly cheap.

Date: Tue, 24 Jan 1995 10:56:55 -0500
From: GNBII@aol.com

Mark Stephens writes:

>I thought I would try and sort out a problem with my T140D over the next month
>or so. The basic problem is that the motor misses badly when you give it full
>throttle. It seems particularly bad around 4000 r.p.m plusÖ.

Try leaning out the idle circuit by using the airscrew. I believe you are just suffering fluffed plugs. Had the same problem on my Commando (strange they act up at about 4000, but mine did the same), and leaning the idle cured it.

Bewley/Atlanta

Date: Fri, 1 Jul 1994 16:48:58 -0600 (CST)
From: Steve Bacon

Howdy,

Another Amal problem is nicks on the sides of the needles. As we all know (if you dont, reach in and wiggle it!) the needles shake back and forth. Well, if you have a bad enough nick (guess what, bad enough here is also known as very little) it may hang up when you let up on the throttle, causing it to idle high. So you turn out the idle screw, and suddenly it won't idle! So examine those needles! I had another problem after I'd had a carb stick (the bike sat for a few days in the cold). What happened was that when it came unstuck, the needle tip missed the jet and was forced (along with that c shaped clip) up into the spring. This cracked the clip right where the needle goes. The crack was impossible to see, until a friend of mine said "oh I gotta replace my clip becasue my carb got stuck..." and when I looked, there's a crack! This can be none too good for holding the needle in place.

Return to the Contents Page

1.13 Carb Syncronising.

Date: Mon, 6 Mar 1995 17:16:04 -0800 (PST)
From: Peter Snidal <psnidal@cln.etc.bc.ca>

Synchronizing carbs isn't difficult. Not even for a PhD. Since I'm currently taking a break from my article on re-wiring your britbike, I'll just pop out a quickie for any of you who don't yet feel confident at it. When this gets boring, just use your N key. Or <Page Down> if you're a Digest Reader.

THE PRINCIPLE

Idea is that all the carb slides should be open the same amount. All shut the same amount. This is only necessary so that all cylinders will be pulling the same amount.

For the non-anal retentive among us [keeping, of course, the Gerbil jokes to a minimum] it will be appreciated that there is no 100% pass on this thing. Reason being that there are other variables besides throttle opening determining the power put out by a given cylinder on a given power stroke. Like valve condition - no two valves are ever going to seal exactly 100% or therefore the same. Ditto for rings, piston clearance, cylinder condition, spark voltage, plug and coil condition, and maybe some other things as well. So the moral to the story is, don't sweat it. You want to ballpark it as closely as possible, but Druids never were hair-splitters. That's why they're Druids. I mean, they used _round_ canoes, for Oak's sake!

So you want to have your throttle slides operating in some sort of equivalence of openness, sure, but differences between considerations involving high rpm and idling will mean there's no perfect setting. Close is Cool.

My personal favourite place to synchronize multiple carbs is at idle. This is because I personally just love the sound of a properly idling motor, and it will never happen if your carbs are out of sync at idle. So here's what you do:

First, you disconnect whatever connects them together. This can be by merely slacking off the adjusters in the individual cables on earlier units, or by slacking off little threaded rods above the carbs on later more multiply-carbureted vehicles. I first learned to sychronize throttles on the Sherman Tank while a high-school Reservist in the '50's, (Footnote: The British Columbia Regiment (13th Armoured Regiment, Royal Canadian Army (Militia) took pride in telling many that we were a Druid Regiment. Honest. Had something to do with our Regimental Padre being the Wrong Kind of Guy for our official Church Building in Vancouver, so we became Druids. Just remembered that. Guess I'm your boy for the Throttle sync story.) and shortly moved on to adapting the technology to my Morris Minor with the homebrew dual carb setup, on to various MG's (2), Healeys (3), Honda Fours ('way too many) (other people's), right up to the Ill-fated 7 carburetter single

cylinder Spagly-Handerthorpe ISDT Special, which requiring Surgical Intervention when operator's parts got in the way, was discontinued shortly before its introduction. In any case, the principle is the same throughout. Start by disconnecting theconnection.

Then, flash the thing up. Hopefully, the above disconnection will still allow a rough opening of all throttles for such, or it will start with an idle throttle opening. If not, advance each of the idle stop screws until the thing does start. Then set it up so that each carburetter is contributing to the running of the thing at idle. You can determine this by fiddling each of the stop screws down in turn until you find one that makes a big difference to the idle speed. This is the one the thing is actually running on. Turn that screw down until you have the lowest possible consistent idle, then turn each of the others up until it too has an effect on idle speed. Once you are at the point where up movement of every throttle stop screw has an effect on idle speed, you're ready to start trying to make them all the same.

One way to do this is to fiddle things until backing each one all the way off in turn has the same effect to idle speed as the others. Meaning, if pulling carb 1 back to nothing makes it stumble and almost stop, but when you return the idle stop to where it was, and pulling carb 2 back to nothing just makes it slow down a tad, then obviously carb 1 was doing a lot more work than 2; advance 2 some, and back 1 off some. (At this point, you are counting turns by the 1/4 as you adjust back and forth.)

Fiddle is the keyword here. This is why we own these things. They are Meccano sets you can ride. If we didn't like fiddling, we'd buy a bike from the Boring Motorcycle Works. (Although they need sychronizing, too, this is generally done by factory trained Black Forest Elves, who, unlike the Druids, worship different Gods and have cuckoo clocks for brains). So you can fiddle away for awhile, and get really close to consistent and equal sharing of the idlespeed load by all carbs.

While you're here, you will want to set the idle mixture screws. Once a given carburetor is admitting air through its slide at the low speed level, adjusting the idle mix screw is supposed to make a difference also to the idle speed. At least, all the books I ever read promised me this. I am still amazed at how seldom this actually has the promised effect. But at any rate, now is the time to investigate this phenomenon one at a time. With the motor idling as slowly as it will, try moving the idle mix adjusting screw on carb 1. The idea is to find a position with which the motor speeds up. If you can actually find one, then drop the newly sped idle back to original by letting back on that carb's throttle stop screw. Then try again, once or twice, and maybe you can even get the speed up more, and back off again on the throttle stop screw. This has happened so seldom to me that I can just about remember all the times, but best of luck. If it did, do the same with the other carbs.

Then check again to try to make it so they are all contributing equally to the idling speed by comparing results when each is backed all the way off. If this kills the engine, then you'll have to precede this little test by raising the contribution of all to begin with - start by advancing all of them 1/4 turn, then backing one off all the way. If the motor dies, put it back where it was (you _were_counting, weren't you?) and give it and the others each another 1/4 turn, etc. It isn't hard to figure out - no more difficult than building a round boat. (Paddling the sucker across a fast river was the hard part.)

Once you're here, you're ready to put it back into riding mode. To do this, just let it cool off for awhile (unless you're fast - I used to amaze my friends by doing this on my MG Twin Cam at Traffic Lights), and then, with the bike idling, tighten each throttle linkage (from the twistgrip - not the idle stop adjustments) until the motor begins to speed up, then back off until slack is barely perceptible. Once you've done all three, check to make sure you haven't made anything too tight by blipping the throttle a couple of times. If it's slow in coming back down to idle, or if it doesn't come back down at all, then one or more of the linkage elements is too tight, slack em off, making sure that the mechanical slack, or lash, is the same for all.

And that's all there is to that. You can complicate matters with air flow manometers (lovely things, those. Add at least $50 to what you can charge for a tune-up. Ask any shop owner. The rip factor/cost ratio is ten times what it is for a scope.), or even a simple piece of garden hose held in the same place at each air horn. (Air cleaners removed.) In this case you listen for the same whistle frequency of the air being sucked past the slide. All three systems described above work only, of course, at idle.

The really hot set-up for racers, of course, is to have proper synchronization at high throttle openings. Presumably, if they're in sync at idle, and all controlled by an opening system with the same mechanical advantage and slack for all, then they're in synch at all openings. However, if you're really anal-retentive [Gerbil Jokers, settle down!], I suppose you could somewhow monitor the compression pressures in each cylinder while the thing's pulling its guts out on a dyno, and adjust the carbs from there. But for the Little People, a simple ensuring of the sharing of the load at idle, followed by making sure the throttle slack is even for all, is completely sufficient.

Somebody keep this. I don't want to have to write it again. And don't send it in to any magazines, comic books, etc., who pay money for this kind of stuff without sending me most of the bread. But feel free to pass it on.

Eh? Enjoy.

From: Mike Taglieri
Date: Wed, 8 Mar 1995 17:35:14 Ė0500

The recent posts on synchronizing your carbs touch on two different theories for doing it:

1. Adjust the cables so both slides are in synch as they rise. Because of manufacturing tolerances, this means they may not give the same idle. (This is the theory behind Bob Cram's post).

2. Adjust the stops on the carbs so each one contributes exactly the same to the idle. Because of manufacturing tolerances, etc., this may mean that one slide is slightly higher than the other. (This is the theory behind Pete Snidal's post, which is easier to follow if you extract the technical parts and delete autobiographical/slapstick material).

What follows is my method, which tries to get the best results with the least mumbo-jumbo, and assumes a twin. (Guys with Tridents can make adjustments):

I normally start by synchronizing the slides, which is easier, and the engine doesn't even have to run. Although you can synch by feel, as Bob Cram suggests, it's easier and more accurate to use a steel rod 1/4" thick or so, either the [unscarred] back end of a drill bit, or a piece of drill rod with the end rounded. Adjust the friction on your throttle so it stays where you put it (or bodge some way to keep it in position if your throttle doesn't have a friction adjuster). Now take off the air filter, and adjust the throttle until the rod will just BARELY pass under the bottom of the slides. In practice, you'll find that when the rod is a perfect sliding fit under one slide, it'll be grossly wrong under the other one. Adjust one throttle cable slightly, open and close the throttle a bit to take up any play, then try the rod again, until it goes under both slides with the same slight, feeler-gauge friction.

Your slides are now in near-perfect synch, although the carbs' respective idles may still be grossly wrong. The next step is to compare these. Check to make sure there's SOME slack in both throttle cables at idle [check at the top of the carbs]. If not, adjust both cables up or down the same amount to get about 1/16" slack [recheck the slides with your steel rod if you're not sure you DID adjust them the same amount]. Now start the bike, and check that both exhaust pipes are getting hot, to ensure that both plugs are firing at idle).

Assuming the bike was in running shape to begin with, there should be some idle at this point. As Peter Snidal explains, each carb should be "contributing to the running of the [engine] at idle." Therefore, find the idle stop screws [the one angled diagonally up], and adjust each one back-and-forth a fraction of a turn. Both should have some effect on the idle -- if one has no effect, that carb is set so much lower than the other that it is not doing its share of the work at idle. To correct this, adjust the "lazy" carb's stop screw up until it does have an effect on idle, but not up TOO much, or the other carb will become the lazy one. Now, if necessary, adjust both stop screws up and down the same amount to get an acceptable preliminary idle.

Once the idle is roughly set, check again to make sure there's still some slack on both throttle cables at idle. Then, adjust the mixture screws [the ones pointing straight in, rather than diagonal] to get the fastest idle, i.e., the best mixture. Snidal said he was "amazed at how seldom this actually has the promised effect," but that's misguided: if adjusting your mixture screw has no effect, your idle circuits are probably clogged with filth. (See what you get when you don't drain your carbs before you put the bike away for the winter?) Try removing the idle screws and blasting the passages out with carb cleaner in a spray can. Ultimately, if you can't clean out the idle circuit this way, you may have to have the carburetor rebuilt.

Assuming your mixture screws work, keep in mind that (on a Concentric) the screw controls the amount of air at idle, and the amount of gasoline is fixed by the pilot jet. 1 to 1 1/2 turns out is the spec, but one of my carbs gives best idle at 3 turns out, so don't be wedded to the book. (Also, the terrible new gasoline that everyone's bitching about may require changes in mixture richness, not only at idle but also needle position at midrange).

Once the mixture is OK, adjust the stop screws up to a fast idle, turning each the same amount. Now you can check to see if each cylinder is doing half the work by cutting off power to the cylinders one at a time to see what happens to the idle speed. My bike's plug wires have Neoprene insulators that are easily removed, exposing the metal connector on each plug, so I can ground each plug in turn to the head with a metal rod to see what happens to the idle [Wear gloves if you do this, and be sure the rod touches the head before it touches the plug, so the circuit will be rod-to-head rather than rod-to-you-to-ground. Also unless you have unusually long arms, you might want to get a friend to use the rod or record the idle speed]. If you use points ignition, you can also cutoff individual cylinders by shorting out individual sets of points, or by pulling the cable off individual plug, but do NOT pull wires off plugs if you have an electronic ignition, because it can be damaged.

Ideally, you should be getting half your idle from each cylinder, and you can fiddle with the stop screws selectively to accomplish this. When the engine is idling well on one cylinder, however, you'll find it idles much too fast on both, so once the two cylinders are adjusted separately, you'll have to back-off both stop screws an equal amount to get your final idle, and you're done.

This all sounds complicated, but in practice you can do part of it, and the results will be acceptable (These are old motorcycles we work on, not the Space Shuttle). In particular, trying to get the idle just right is useless if the carbs are worn, so the most practical thing for bikes with old carbs (like mine) is to get the slides in synch, then touch up the idle on the road if it wanders off, bearing in mind that with worn carbs, the "lazy" one that's idling too low may vary from day to day, or even minute to minute).

Finally, Bob Cram mentioned that you should feel inside the carbs to be sure that the two slides are STARTING to move at the same MOMENT. Unfortunately, this may be impossible to achieve, since adjusting the idles individually probably means the two slides are not starting at the same height. Since the cables are adjusted so they WILL be at the same height at throttles other than idle, the slide with the least slack in the cable will necessarily start moving first. Instead of the way I described, you could adjust the idle first, as Peter Snidal suggests, then adjust the two cables to get the same amount of slack, without concern for synchronizing the slides exactly. This would get the two slides moving at the same moment, and might give more even running just off-idle, but the slides probably would never be at the same height throughout the range, which would compromise even pulling at speed. For the kind of riding I do, I care more about even pulling throughout the range, and am willing to sacrifice some smoothness off-idle. Others may have different priorities.

Mike Taglieri

From: Frank Jkosz
Date: Thu, 09 Mar 95 08:31:45 CST

As with computer I'm sitting at, I thought that I'd apply some higher tech to tuning the bike so I bought a mercury carb syncronizer. It was $35 and well worth it. I can adjust the bike's idle and part throttle syncronization without removing the air cleaner.

Eric, how about posting your procedure for using your mercury carb synchronizer for synching your carbs? Sounds like the way to go -

Thanks,

Frank

Date: Thu, 9 Mar 95 09:37:37 +0000
From: Bob Cram

Mike writes:

>Finally, Bob Cram mentioned that you should feel inside the carbs to be sure
>that the two slides are STARTING to move at the same MOMENT. Unfortunately,
>this may be impossible to achieve, since adjusting the idles individually probably
>means the two slides are not starting at the same height.

He's right. I didn't save my original message so I can't remember exactly what I said. What I wanted to say, and probably didn't do so very clearly was that in playing around with the slides and the throttle stop, you really need to seek to achieve a balance between what happens at idle, what happens as the slides start to rise, and what happens as the slides rise the rest of the way. It would be virtually impossible to get perfect sychronization at all these levels, so it depends on what you want, when. Peter likes a perfect idle. Mike likes best synchronization at mid-range.

I'm probably more inclined to mid-range synchronization too, but I always tend to spend a lot of time fiddling to get that balance of all three. In fact, I always take a look at to see when the slides hit the top of the rise in relation to one another too. If the timing of that is quite different, then I play around somewhere.

Date: 9 Mar 1995 10:03:28 U
From: Eric RoggeSubject

Reply to: RE>>Re Carb Syncing (long).

In response to Frank's request, here's my home-devised method of using my carb syncronizer:

1. Get the bike idling or close to idling somehow. You can use whatever method you choose. Make sure it's at operating tempurature.

2. Connect the carb synchronizer and check the respective mercury levels. A higher level means a lower slide. So, if your idle at the start is above your desired rpm, then lower the high slide (indicated by a lower mercury level). Raise the low slide if your idle rpm is lower than what you want.

3. Check the idle speed air/fuel mixture. If you can raise the idle rpm by changing either screw, you will need to lower it by decreasing both slide heights. Go back to step (2) to do this.

4. Raise your rpm to about 3000 to check that each slide is rising together. At a steady 3000 rpm, the mercury levels for both cylinders should be even. If not, then adjust the cable adjuster up for the carb with the higher mercury level (or do the opposite for the other cylinder). Make sure you have cable slack at idle.

So, now you have idle and 1/8-1/4 throttle sync'd. This begs the question about what's going on at full throttle and at just off idle:

Full Throttle - I checked my slides both visually and with my fingers at full throttle after the first time I used the synchronizer, and it was darn close.

Off Idle - For me, at off idle the mercury levels differed about 1/2 inch, with the difference decreasing as I rolled on the throttle. This validated my concern about my sticking cable. Once I fixed the cable, off idle was dead on.

Foot Note - I would suspect that bikes which have significantly different compressions in each cylinder may not be sync'able with this process, since the cylinder with the lower compression may not lower the intake pressure equivalently.

Cheers!

Eric Rogge

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