2.1 Removing the Cylinder Head.

Date: 07 Feb 94 19:18:00 -0500
From:Guy Fortier

Well it finally got warm enough around here in south eastern Ontario (-5C) to be able to go out the garage and start the long over due winter maintenance to theCommando. So I bundled myself up, poured a nice shot of JD and made my way out to the garage. When I got there I found the Commando covered in frost, or at least the parts I wanted to work on were covered in frost, so after wiping down the affected areas I began taking off the cylinder head so I could have the exhaust ports rethreaded.

Everything came apart easily due to having coated all the studs with copa-slip during the last re-build. It only took about an hour to remove the head (including removing gas tank,coils and carb), I think I'm getting pretty good at it, seeing this my third time removing the head. Both previous attempts were caused by head gasket failures (composite material variety's), I now use the big thick copper gaskets. Although they may leak every once and a while, they won't blow out like the composite ones. Well now that got this much done it's time to call the machine shop and arrange to have the work done.

Date: Mon, 28 Feb 94 14:50:36 EST
From: John Pinkham.

After installing a Boyer ignition, I was about to time my 850 Norton when I noticed a rapidly enlarging puddle of motor oil coming from the front of the engine after a few minutes of running. It appears to be coming from the head gasket area. Anybody else ever experience this phenomenon? If I had followed the Clymer manual, I would have retorqued the head bolts before I adjusted the valves, etc. Unfortunately this job appears to require a Whitworth socket which I didn't have. Also heard that the Commando front head studs tend to strip out. HeliCoils ?

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2.2 Port and Polish the Cylinder Head.

Date: Wed, 2 Mar 94 06:07:04 PST
From: dwhite@atl.com (David White)

I have a pre-unit Triumph Tiger engine with a Bonneville head. I want to get it ported.

Appreciate input on;

Date: 02 Mar 1994 13:35:10 -0500 (EST)
From: Pete Serrino 

In response to Dave White's "dwhite@atl.com" inquiry on porting his Triumph:

Dave, let me put my two cents in. I am speaking as an non-professional with 35 years experience tinkering with motors, reading a lot, and paying attention at the rally tech sessions. Porting should be left to the pros. Limit youself to matching all the ports (carb to mainfold, manifold to head, and exhaust port to exhaust pipe).

You can probably get away with smoothing any rough castings in the head and manifold but it is important not to change the shape of the intake port. The finish on the intake side should be no finer than 400-600 sandpaper would produce. The exhaust will benefit from polishing. A polished surface if applied to the intake would actually increase surface tension, attract fuel droplets, and slow the flow at the surface.

Same princple is applied to golf balls. A smooth ball would provide more drag (I believe it has something to do with Hemholtz Effect) My experience is with Nortons so I can't help you with valve choices. Most experts now adays think the cast iron valve seats are fine with current fuels.Your valve guides will probably need to be replaced before the seat goes.Cams and porting should be thought of as a package job.

Changing one item (carbs, cam, port shape, exhaust shape and length) requires changing all of the components if maximum benefit is to be gained. Otherwise a gain in one area will usually cost you somewhere else. I believe Big-D cycles in Dallas, TX are still among the premiere Triumph tuners in the US. Also Leo Goff in Memphis,TN is excellent. You should try to get a hold of his articles in the TIOC-BIMA newsletter in particular the one on valve seats which was done within the last six months. (sorry I am not a member and don't know which one for sure) As far as all of this stuff working Leo is now getting over 100 rear wheel horsepower from an ~900cc, pushrod, normally aspirated Norton motor on gasoline. I would invite and welcome any more opinions/input on these topics.

Date: Wed, 2 Mar 94 13:45:11 CST
From: Bruce Graham

David White asks:

>I have a pre-unit Triumph Tiger engine with a Bonneville head. I want to get it
>ported. Are you using a latemodel 9 bolt head?
>Appreciate input on; Wether polishing realy does much.

You really need to find someone with a flow-bench and a lot of knowledge about carbs, exhaust, cams, compression, etc to help on porting/polishing issues. I think that just matching inlet ports is the easiest way to improve performance.

>Valve choices.

I believe you can get larger valves installed on the later model heads. The valve seats will have to be recut for the new valves. Standard valves seem to work fine for non-race applications.

>Unleaded conversion.

An unleaded conversion would make sense if you plan to do a *lot* of riding, or if your current valve seats are already recessed/over-cut so that you are having valve shrouding problems. If your valve seats are in good condition I would leave them alone and monitor the wear (watch valve clearances).

>I have stock cams, if the head work is done for the stock lift what choices do I have
>for a hotter cam in the future?

You have a lot of choices for cams. It all depends on what you plan to do with the bike. The cam I am using is a megacycle (1060 I think) which is a mild grind for street use. If you go with a non-stock cam, and a hi-comp pistons, you may need to remachine the valve cutouts in the pistons.

>Who does a good job on this stuff?

Big D Cycle (in Dallas Tx) can do all the work, make all the recommedations, and provide all the parts. Their work is execellent. Just tell them what you are trying to build (stock, street, race, etc). Jack Wilson (owner) has been racing Triumphs for many, many years.

Be prepared to spend some bux. BIG D CYCLE 3600 W.DAVIS DALLAS,TX (214)339-2285 REPAIR/PARTS/RESTORATION Good luck, let us know how it works out.

Date: Wed, 2 Mar 94 15:46:17 PST
From: Graeme Harrison

>>I have a pre-unit Triumph Tiger engine with a Bonneville head. I want to
>>get it ported.
> Are you using a late model 9 bolt head? The pre-unit 650cc twin with a late model 9-bolt Bonneville head gets my vote as the most beautiful Triumph engine. There's a excellent shop down in Southern CA called Branch Flowmetrics which would be just the ticket for porting/polishing that head. Depends on whether Dallas, TX or CA is closer as well as price, too. Don't have address for Branch, but will dig it up if interested. A good number of Britbike shops will act as a middleman for porting/polishing work so ask and see which vendor they use as well as how much they'd want for handling it.

A vendor may give the dealer a discount which would be the dealer's cut meaning customer may not have to pay extra for going thru dealer. YMMV.

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2.3 Bigend.

From: MikeTnyc@aol.com
Date: Sat, 21 Oct 1995 12:59:11 -0400
Subject: Re: My Friday the 13th (long)

Lord, what a hellish mess!  (I thought I had problems when I discovered Raul needed a ring job).  Would I be correct in guessing that your fragged main bearing wasn't a Superblend (#NJ306E -- the pre-Superblend bearing doesn't have the "E").   These weren't stock until late '72, so your bike didn't have them originally, and a pre-Combat engine might have lasted 'till now without them.

If you find the bearings aren't Superblends, replace them both, (however good the other one looks), and don't let anyone talk you into anything other than the genuine FAG bearing, #NJ306E.

If you find that the failed bearing WAS a Superblend, I'm not sure I want to know about it.  They're supposed to last 100,000 miles, and I still have 90 K to go.

Mike Taglieri

Raul -- '72 Commando Interstate (whose original bearings were so pockmarked when they came out that they looked like the surface of the moon. . .)

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2.4 Cleaning up Piston Meltdown.

Date: Fri, 18 Mar 1994 10:26:44 -0800 (PST)
From: Tim Keane

I'm finally getting around to rebuilding the engine on my '67 TR6R. A couple years ago this engine had the most drastic failure I've personally encountered, and I was so bummed I just set it aside (besides, I had just acquired the JPN and was more interested in it).

The engine failed when the left piston melted, leaving a long aluminum spooge streak down the cylinder wall (you'd have to see it to appreciate it). So I took the barrel down to the local Triumph shop to check on getting it bored another 010, and Steve (the service guy there) said that I should first clean off the aluminum spooge with some kind of acid -- he can't remember what kind. So... any ideas on what kind of acid would clean the aluminum off without harming the cylinder wall or me (and where I can acquire it)?

Date: Fri, 18 Mar 1994 10:44:39 -0800
From: Alastair Young

Tim Keane said:

>I'm finally getting around to rebuilding the engine on my '67 TR6R. Etc.....

Try caustic soda. This is used to clean rust off cast iron and I remember being warned not to let it near ally because it eats it. Don't know how "caustic soda" translates into Amerispeak though.

Date: Fri, 18 Mar 1994 15:04:59 -0500 (EST)
From: Pete Serrino 

Alastair Young said:
>Try caustic soda. Etc...

Caustic soda (aka Sodium Hydroxide) will work to remove aluminum. I almost disolved my Norton head in it trying to remove some carbon.

Date: Fri, 18 Mar 94 17:18:27 -0500 (EST)
From: Latte' Jed Right!

Caustic Soda, AKA lye, AKA drano! It eats aluminium and leaves steel, I remember this from the time I tried to etch PC boards in a disposable roasting pan.

Date: Fri, 18 Mar 1994 21:25:42 -0800 (PST)
From: Peter Snidal 

On Fri, 18 Mar 1994, Latte' Jed wrote:
>Right! Caustic Soda, AKA lye, AKA drano! It eats aluminium and leaves steel, I
>remember this from the time I tried to etch PC boards in a disposable roasting pan.

I knew a guy had a Matchless single that had been raced a lot, and had Castrol R burnt to the Cylinder head real bad. He left it soaking in caustic soda overnight, and the next day (or two) all he found was the bronze combustion chamber liner. The Al was gone. This can be hard on your attitude.

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2.5 Inside the Timing Cover.

From: "D.J. Walker" <djw12@leicester.ac.uk>
Subject: Combat Cams - identifying thereof
Date: Fri, 28 Jul 1995 17:05:09 +0100 (BST)

Dear All, In response to this problem of identifying the Combat's 2S cams, I rang Les Emery about this just now, and he says the old 2S cam*should* bear the stamp "S S" on the left hand end lobe area. This is a little confusing, since I wrote earlier saying that a 2S cam should never be described as an "SS", since an SS is the 650SS Dominator cam.... etc. But there's the manufacturer, gone and stamped "S S" on the damn things!

The cams from bikes in the low 200,000's (engine numbers) had plain ends and scrolled bearing bushes, as opposed to scrolled end and plain bearings, which is the normal setup. He agreed that the latter system is the better of the two, because it simply provides better lubrication. The 2S cams his company now manufactures all have this arrangement (as do all his other camshafts, of course).

His opinion of the 2S camshaft is rather low, and he reckons it's the least useful of the lot, as far as usable performance goes, whilst tending to put greater strain on the valve mechanism. The inlet cams of the S, 2S, 4S and 7S have each got successively greater lift than each other, running in that order. Someone has already said that the S has .332 lift, the 2S has .380, and as a matter of interest, the 7S, high performance cam has .470 lift. The 2S doesn't give enough power for its increased problem-potential, apparently. Why not see about a 4S, if you're thinking of changing it, or going to the gentler S-setup?

I mentioned to him that the Combat in question still had the old main bearings setup, and he said this showed the bike must have been run at high revs for much of its life. At a consistent engine speed of over 4000rpm the old setup is fine, Les told me, but if the bike is chugged around at 2-3000rpm, the bearing''ll give way. Either way, snapping of the crankshaft is more likely with the old setup, if you realy thrash it. I guess everyone knew this anyway, but it's nice to hear it from one of the experts.

Sorry I couldn't be of any better help, Steve. Anyway, I'm off for the weekend.

Commando Dan
djw12@leicester.ac.uk

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2.6 Replacing the Cam Chain Tensioner.

Date: Thu, 4 Jan 1996 13:50:02 -0500 (EST)
From: kaak@inforamp.net (Klaus Kaak)

to all my knowledge a replacement is not only possible but also strongly recommended. your bewilderment ( metal on metal ) is very justified!

I've been using the standard tensioner for years.  It's only the edges of the plates that rub on it, and do so when it's not under tension.  I have virtually no chain adjustments for thousands of miles.  Can someone tell me whether it is actually the consensus that this thing ought to be replaced?

I've been using the standard tensioner too (I have an early '69 so there isn't much choice since the bonded face type only seem to be available for the later single timing chain motor).  I rode the bike for 90,000 miles before replacing it with a good used one because the rollers were getting too close.  I have no idea how much over that 90,000 it had been in the motor.  It's quite possable that it was the origonal and therefore had about 190,000 miles on it.  Obviousley I wouldn't bother.

hi colin,
i didn't know that there was anything other than a single timing chain.how
long did norton use a double rowed cam chain? my reply referred to single chains & I believe that the bonded tensioner will give best service here.thanks for illuminating me!
Klaus

From: DDODGE <DDODGE@nvn.com>
Subject: camchain and sprockets

My '72 still has the steel slipper, but I've been afraid to get the rubber one because of the very problem mentioned here: the rubber can fall off and cause a dramatic loss of tension in the chain, especially since the metal underneath is not hardened.  One guy in Classic Mechanics some years ago brazed a narrow brass track to the steel shoe so the chain rollers would roll over the shoe rather than the sideplates sliding on it. There's also a third kind: a company called RMA Engineering (408/578-4032) advertises in Norton News (magazine of the US Norton Owners Assoc) an automatic cam-chain adjuster that replaces the slipper with a spring-loaded molybdenum disulphide-filled nylon shoe and costs about $70.00 -- you never touch it again after you put it in.

I thought all those slipper things worked by having the chain rollers roll/slide over them, it being expected that the chain plates would immediately wear grooves in slipper. At least that's the way I remember the primary in the Vincent worked.
dannysore

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2.7 Adjusting the Cam Chain Tensioner

Date: Wed, 11 May 94 14:26:44 BST
From: Peter Azlan <pa@gx2.uk.mdis.com>

It's not that I enjoy the frustration of engine manitanance, I just feel you need to be in the right mood, or to be more precise, the right frame of mind.

There are times when nothing goes right, there is always that one bolt or screw that just won't budge, but you persist, then things really take a turn for the worst. In your heart, you feel you just need to 'fix this bit', or 'undow that screw' and it will all start going right, but it never happens, not on that occation anyhow.

There is probably some deep carmic (sp) reason for this, maybe its the phase of the moon, maybe its your biorhythms, the tides or what you've been eating. The thing is, the bikes working together with this force, and what you really should learn to do is give up when this happens, but of course you don't, and things go from bad to worse.
 

Setting the Cam Chain Tension on the Commando.
According to the manuals, this task should be tackled every 5K miles. The notes that follow refer to a Mk 2, or pre electric start commando, Mk 3 Timing covers have a little inspection cover that looks like it's for checking the tension without all of the following. You can probably fit a Mk 3 cover to earlier engines, and get the built in anti-drain valve, but it costs about 70 pounds and you start to worry about originality, and whether the bike is going to be the same bike you originally bought.

The first thing you start to ask yourself is, why use a chain, wouldn't it be better to use an intermediate gear like the Triumph twin Edward Turner designed ?

Anyhow, how I did it the first time:

  1. Remove the side pannel covering the oil tank and drain the oil.
  2. Undo the magnetic sump plug and drain the sump.
  3. Remove the Primary Chaincase timing degree inspection cover and  turn the engine to 30 Deg, mark the rota, there are two marks remember. [This is because you will be marking other 'stuff' for re-assembily and the engine will probably turn while working on it]
  4. Remove the gear indicator and lever.
  5. Unscrew the points cover.
  6. Mark the points backplate and timing cover to aid re-assembily.
  7. Undo the two piller bolts and remove the points set complete. I cut the wires to the points, could'nt see how I could remove the timing cover and work on it otherwise. [I know the manual says you can pull the wire through, but it was simpler for me this way, I have a soldering iron.]
  8. Mark the position of the auto advance on the inside of the case, again to aid re-assembily.
  9. Remove the long bolt from the center of the auto advance.
  10. Put the bolt back an inch or so and tap the end a couple of times  from above to break the taper and free the auto advance, light taps are all that's required.
  11. Remove the banjo bolt that feeds oil to the rockers.
  12. Undo all the screws retaining the timing cover. [The timing cover is located with two dowles so no side blows with a rubber mallet will move it, and may actually damage it]
  13. From the other side of the engine, tap the oil pressure releif valve and that bit of the timing case at the front that protrudes, (is proud of), the crancases away from the engine. This is to break the old gasket and free the timing cover.
  14. Realise you should have put something down to catch the oil from the timing case.
Once inside, you are now able to check the tension on the Cam Chain.

There's a small gear on the end of the crancshaft, timing side, which drives a larger gear immediately above called the intermediate gear This is used to achieve a 50% reduction in speed and change in direction. The intermediate gear has a sprocket attached which drives a chain which then drives a sprocket on the end of the Camshaft and thereby the camshaft. There's a sliper tensioner on the lower, or return run of the chain. This is to reduce backlash in the camshaft and improve the lifespan of the auto advance.

In Bacon’s book on restoring Norton Twins he goes on and on about how you can't set the cam chain tension with the cover off as there is nothing to support the intermediate gear shaft, the question is, If you haven't got a scrap timing cover, with holes cut in it for this purose, (and very few people have) How are you going to set free play ?

The correct free play is, 3/16" slack on the top run of the chain, check in several positions, when correct torque the adjuster nuts to 15 Flb.

My cam chain was so slack the top run had started eating into the top adjuster nut. On closer inspection, I found the rubber face of the adjuster lose at the bottom of the timing chest, the chain was also eating into the steel face of the adjuster.

Now the bad news, assuming you have to replace the slipper tensioner: This won't come off with the chain in place. Yeah I know the manual kinda looks like it does but I couldn't manage it. It does move about a bit, in a tantalising sort of way, but it realy wont come off without removing or displacing the camchain. To remove or displace the chain (to allow the adjustor to be removed) you have to remove either the sprocket on the end of the intermediate gear, or, the sprocket on the end of the camshaft, or both.

Although there is some side to side movement, the sprocket on the intermediate gear, and the intermediate gear itself, cannot be slipped off the intermediate shaft as the gear hits the spiral, or worm drive for the oil pump. If you chose to remove the intermediate gear remember, the oil pump worm gear has a LEFT HAND THRED.

The sprocket on the end of the camshaft is retained with a nut and located with a wodruff key. If you decide to remove this sprocket you will first have to remove the nut. When you do remove the camshaft sprocket nut, APPLY ONLY CONSTANT PRESSURE. Don't bash the spanner with a hammer to try and  'shock' the nut free, as this may tear the intermediate gear shaft out of the crankcase. You will need a good fitting socket or spanner for this, I have noticed that most sockets have a radiused opening which doesn't allow the socket to fully engage on the nut, allowing it to slip off all too easy. Once the nut is removed, the sprocket can only be removed with a small two leg gear or sprocket puller.

A note of caution, if you decide to pull the camshaft sprocket first this will pull the chain and intermediate gear out a little where the intermediate gear will start to interfere with the worm drive for the oil pump on the end of the crankshaft. If you then attempt to remove the worm drive, and this is usually a very tight fit, the interferring gears will start to cross mesh and distroy each other.

Thing is, if you do pull the camshaft sprocket, you can get the tensioner out without touching the worm or oil pump, just remember the to stop the worm and the intermediate gears cross meshing and eating eating each other.

Apparently there are two different types of slipper tensioner. The earlier one is plain steel, the later one is steel but with a rubber face. To me the later one is more attractive, I'd rather have bits of rubber floating around the engine than bits of steel.

While the timing cover is off you may chose to replace the oil seals located therein. The Oil Seal for the points can be prised out with a screwdriver, I drifterd in a new one with a socket of the right size, this goes spring towards the engine. Dont forget to spread a little gasket goo on the outsie of the seal to prevent oil escaping round the outside. Later  points oil seals are red in colour, and are considered better quality.

The oil seal for the end of the crankshaft is retained with a circlip. Once the circlip is removed, you can prise the oil seal out with a screwdriver. This seal goes in with the spring, or gater, the other way round, pointing away from the engine. Again, I drifted mine in with a socket of the right size and a small hammer. The socket needs to be large enough so it bears down on the outer edge of the seal, but small enough so it clears the hole in the casting. When the new seal is in, don't forget the circlip, which should be fitted 'sharp' edge away from the seal.

It is recommended that the little rubber seal on the end of the oil pump, is replaced every time the cover is removed and replaced. This seal is responsible for maintaining oil pressure to the crankshaft, and thereby the engine, it only costs about 50 pee, (uk) so why not replace it every time ? There's a lot of talk about this seal in the manuals, it needs to be a good tight fit. On some engines this was achieved with shims or washers fitted under the seal, in later engines a gasket was fitted behind the oil pump. Just lookout for the shims/washers and put them back if fitted.

When I replaced the camshaft sprocket and nut I torqued the nut down to 70Flb, there was no figure given in the manual but this seems reasonable. I never did get the worm gear with its left hand thred off. I wasn't able to lock the engine well enough by puting it in gear and applying the back break, I guess this is a job to be tackled when the engines out and I can replace the camchain at that time too. Removing the camshaft sprocket gives enough access to remove and replace the slipper tensioner.

One other thing, before you replace the timing cover remove any remnants of the old points seal from the shaft, a little ring of rubber collects there. And dont forget the service tool which protects the points oil seal when re-fitting the cover.

Once re-assembled, I have found two documented ways of providing initial lubrication to the engine and priming the oil pump, (you need to prime the pump if there is no oil in it). The first, and possibly simplist, is to remove the intake rocker cover, and fill with oil. It looks like this then drains down the oil return and into the timing chest, not sure if this primes the pump though.  The second involves priming the crankshaft with oil via the rocket feed banjo and pipe with about a 'tea cup' (yes, that what it says in the manual), full of oil through an oil syringe ? I'll let you know how I get on.

HOW I WOULD DO IT AGAIN NOW I HAVE DONE IT ONCE:

  1. Run the engine to clear the sump of oil.
  2. Remove the Primary Chaincase timing degree inspection cover move the engine to 30 degrees and mark the roter.
  3. Remove the points cover.
  4. Mark position and remove the contact breaker base plate.
  5. Mark position and remove the auto advance.
  6. Remove the gear position indicator and lever.
  7. Remove the oil feed banjo to the rockers.
  8. Remove the 12 screws that hold to timing cover and remove the cover.
 When the cover is off, oil will seep from the drilling in the crancases, blank this off. Also plug the end of the crankshaft to stop all oil from draining.
  1. Set cam chain tension, should be 3/16".
  2. Re-tighten the tensioner nuts to 15Flb.
  3. Fit a new cover gasket and cement.
  4. Fit the points oil seal guide.
  5. Remove oil feed blanking and crankshaft plug
  6. Replace the timing cover.
  7. Replace gear lever and pointer.
  8. Replace auto advance, and points.
  9. Set points gap and ignition timing.
Regards Peter Aslan, aka Captain Norton.

From: MikeTnyc@aol.com
Date: Fri, 13 May 94 02:13:04 EDT

Apparently there are two different types of slipper tensioner. The earlier one is plain steel, the later one is steel but with a rubber face. To me the later one is more attractive, I'd rather have bits of rubber floating around the engine that bits of steel.

I believe the purpose of the rubber-covered slipper was mostly to reduce noise rather than protect the engine from steel particles -- Norton had trouble with EPA and English noise standards during this engine's last years.   My '72 still has the steel slipper, but I've been afraid to get the rubber one because of the very problem mentioned here: the rubber can fall off and cause a dramatic loss of tension in the chain, especially since the metal underneath is not hardened.  One guy in Classic Mechanics some years ago brazed a narrow brass track to the steel shoe so the chain rollers would roll over the shoe rather than the sideplates sliding on it.

There's also a third kind: a company called RMA Engineering (408/578-4032) advertises in Norton News (magazine of the US Norton Owners Assoc) an automatic cam-chain adjuster that replaces the slipper with a spring-loaded molybdenum disulphide-filled nylon shoe and costs about $70.00 -- you never touch it again after you put it in.   I did a camchain adjustment last about 6,000 miles ago, and I'm grateful to Peter Aslan for reminding me what a hellish mess it can be.  Maybe that'll get me to finally buy this contraption, so next time can be my last.   USNOA is a great club, by the way -- the magazine alone is worth the dues.  (412/376-4266).

2 other points:

1. If you don't have the service tool to protect the points-seal, you can get by with a smooth socket, 14mm socket or so.  Push it gently into the points-seal, and it will fall out as the cover goes on, protecting the seal from the sharp edge of the cam.

2. Once you go to the trouble of getting all this stuff off to reach the slipper, it's not much more work to remove and rehab the oil pump to eliminate endplay on the gears.  I'm not really sure why the oil pump would have to be primed if all you were doing was adjusting the slipper, but after a rebuild you can pre-prime it by filling it with Vaseline.  This moves out quickly when you start, and once it melts and dissipates, it never solidifies again.

Subject: Tech Tip: Engine Locking
Date: Mon, 6 Jun 94 14:31:06 EDT

A few weeks ago, Colonel (then Captain) Norton shared the pleasures of adjusting the cam chain tension on his Norton with us. He said that he was unable to remove the oil pump drive worm because he could not lock the engine up enough to turn the securing nut (left hand Whitworth, of course). Well, Commodore, there is a way. Read it in the instructions for the automatic cam chain tensioner, I recently invested $80 US in. Here's how: Remove one sparkplug. Bring that piston to halfway up. Pour in engine oil until the volume is full. Replace sparkplug. Quickly remove worm nut, remembering that it's left hand thread. The hydraulic lock will gradually dissipate by leakage past the rings. Syphon if you are in a hurry.

Wonder if an air impact wrench might work also

Private Norton

Date: Tue, 7 Jun 94 08:16:00 BST
From: Peter Azlan <pa@gx2.uk.mdis.com>

This mail is really to Private Norton, (John Pinkham). Who tells us all of the existance of an automatic cam chain tensioner for the Commando.

Having aroused my curiosity, just how does one work, are they suitable for the good old Mk2, or just the Mk3 Commando, and where can I get one from ?

On the Isolastics, there are different Shims for the Front and rear, remember to adjust them off the center stand, and I always use something like a crowbar to force the engine to one side to allow a measurement to be taken.

As the Shims are different sizes, I suspect the Vernea (Sp) stuff is different front and back also.

When adjusting, the manual says 10 thou, the Blighty Police always set theirs to 6 thou, and the best advice is, as tight as possible (<10 thou) ensuring the vibration is bareable, and that there is some movement in the mounts, otherwise frame damage, (broken welds) will result. A real improvement in handling can be achieved with the Norvil Head Steady and mk3 type fixing the swinging arm (fork) spindle with more nuts and bolts.

Regards Captain Norton.

From: MikeTnyc@aol.com
Date: Fri, 10 Jun 94 01:17:36 EDT

I've noticed that several writers keep asking where to buy the automatic cam chain tensioner they've heard about for the Commando [or maybe it's the same guy over and over?], so I'm repeating the piece I wrote on this unit around May 15th, for their/his convenience.  Everyone else, please ignore.

There is "a third kind" of camchain tensioner besides the metal and rubber-covered slippers: "a company called RMA Engineering (408/578-4032) advertises in Norton News (magazine of the US Norton Owners Assoc) an automatic cam-chain adjuster that replaces the slipper with a spring-loaded molybdenum disulphide-filled nylon shoe and costs about $70.00 -- you never touch it again after you put it in.   I did a camchain adjustment last about 6,000 miles ago, and I'm grateful to  Peter Aslan for reminding me what a hellish mess it can be.  Maybe that'll get me to finally buy this contraption, so next time can be my last.   USNOA is a great club, by the way -- the magazine alone is worth the dues.  (412/376-4266)."

Since then, I've looked in more recent issues of Norton News, and see that the unit is now $79.95 ($5 more/Canada; $10 more / England).  Recent ads say, "maintenance free, dampens cam chain vibration; holds valve and ignition timing precisely; proven performance in over 12,000 test miles."  I figured anyone who wanted this would call first, but some of you overseas folk may not want to, so the address is: RMA Engineering / 447 Santa Mesa Drive / San Jose, Ca  95123.

Again I must stress that I have no connection with these people and do not own this device, although it's gotten good reviews and I may someday buy one.

{P.S.  Thank you all for calming my fears about Raul's fiberglass tank; it sits very near to organs vital to human happiness, and I'm glad it's solidly made].

Michael Taglieri
Raul -- '72 Commando Interstate
CAMCHAIN

From: John Bria <johnb@hpmva069.nsr.hp.com>
Subject: Re: auto camchain tensioner / rerun

There is "a third kind" of camchain tensioner besides the metal and rubber-covered slippers: "a company called RMA Engineering (408/578-4032) advertises in Norton News (magazine of the US Norton Owners Assoc) an automatic cam-chain adjuster that replaces the slipper with a spring-loaded molybdenum disulphide-filled nylon shoe and costs about $70.00 -- you never touch it again after you put it in.   I did a camchain adjustment last about 6,000 miles ago, and I'm grateful to  Peter Aslan for reminding me what a hellish mess it can be.

Michael Taglieri

I've had one on my MK2A for about 10K miles (won it at a NCNOC Christmas party) and have had no problems, no adjustments ... kinda don't know it's there except for the decreased maintenance.

Date: Fri, 10 Jun 94 16:04:58 EDT
From: John Pinkham

Just to add a bit to previous posts by John and Mike to the subject:
The cost of the automatic cam chain tensioner is $79.95 US including shipping and handling (might need a bit more to ship it to Blighty). The address is RMA Engineering,447 Santa Mesa Drive, San Jose, California, 95123. Tele: (408) 578-4032. Lady answers with crying baby in background. It comes with *good* instructions, 6 pages of 'em, well illustrated. The device consists of a mounting bracket which hold a spring loaded wedge. Keyed to the wedge is the nylon shoe, impregnated with solid lubricant. Only metal removal is said to be the lower dowel pin boss ( use a, pardon the expression, bastard file for this).  Have new oil pump seals, etc. On hand before commencing the project.

Go for it!

Return to the Contents Page

2.8 Priming the Oil Pump.

Date: Mon, 16 May 94 18:17:03 BST
From: Peter Azlan <pa@gx2.uk.mdis.com>

Following the cam chain saga, (I must get one of thoes automatic tensioners), I have to admit that, yes, the oil pump was removed at some point. And yes I did give the drive shaft a twiddle out of curiosity to
watch the oil spurt out, and no I'm not sure it was fully primed with oil when I had finished.

So, having replaced the timing cover, I filled the tank with Oil and left it overnight. I thought that the thing would wet sump and sort of prime everything. Saturday arrives. Out to the garage and an inspection of the Oil Tank Dip stick and oil feed to the rockers, (this is via a transparent pipe). No Oil appears to have left the tank, therefore no more oil is in the engine than the night before, not quite what I would have expected, and certainly not what I had hoped.

Surely it can't harm the engine if I run it for a bit and see what heppens. So I started it and looked expectedly at the oil feed. Nothing. Stop the engine before it gets hot, all sorts of images start
flying around my mind, bronze bushes running dry, moltern pistons.

Right, there's nothing else for it, i'll have to prime the pump.

Now the manual has this Oil Syringe thing that looks like a bicycle pump, visions of modifying an old pump or even using a lenth of tube and forcing the oil down with gravity come to mind.

In the end I unscrewed the lower rocker feed banjo, the one that screws into the timing cover, pulled off the rocker feed pipe and connected a short lenth of tube from a brake bleeding kit, (just plain
transparent pipe). Then screwe the banjo, washers and oil feed back onto the timing cover. Next I looked furtively around the garage for somthing to pump the oil.

From the corner of my eye I notice a small oil gun, the sort with a trigger hand action and a long thin spout. Aha, filled the gun with fresh oil, stuffed the long thin spout up the other end of the pipe and pumped till the gun was exausted. This worked remarklably well, I was able to push loads of oil into the pump with little resistance, just enough to tell you the pump was there.

It was then a simple matter of removing the banjo, removing the pipe, cutting about 1/4"" from the end of the oil feed pipe, (so as to connect with a new and decent bit of pipe),  heating it in boiling water to sofen it up before remating it with the banjo and oil coupling.

You could immediately see the oil rising in the rocker feed pipe, and when I started the engine, the oil pushed its way up the pipe and into the rockers. 50 Miles later all is fine, timing the engine with a
strobe showed a much more consistent flash, less slack in the chain, (till the rubber face decides to go for a walk).

Regards Peter Aslan aka Captian Norton.

Date: Wed, 18 May 94 17:58:26 EDT
From: John Pinkham <John.Pinkham@lambada.oit.unc.edu>

Since motorcycle oil pumps are rotary positive displacement types, they should be self-priming. Just remove the sparkplugs and use the kickstarter to motor the engine. Or put the bike up on the kickstand in 4th gear and rotate the rear tyre. So why bother injecting oil down rocker feed pipes, filling the pump with Vaseline, etc?

Date: Wed, 18 May 94 17:43 EDT
From: mason@ftp.com (Latte' Jed)

> Since motorcycle oil pumps are rotary positive displacement types, they
> should be self-priming. Just remove the sparkplugs and use the kickstarter
> to motor the engine. Or put the bike up on the kickstand in 4th gear and
> rotate the rear tyre. So why bother injecting oil down rocker feed pipes,
> filling the pump with Vaseline, etc?

I remove the spark plugs and push the bike up and down the street to get the juices flowing. It looks stupid but it makes sure that everything's fully lubed.

From: ralph@swmerc.rain.com (Ralph Merwin)
Date: Wed, 18 May 94 15:31:19 PDT

John Pinkham writes:
>
> Since motorcycle oil pumps are rotary positive displacement types, they
> should be self-priming. Just remove the sparkplugs and use the kickstarter
> to motor the engine. Or put the bike up on the kickstand in 4th gear and
> rotate the rear tyre. So why bother injecting oil down rocker feed pipes,
> filling the pump with Vaseline, etc?

I think that when they have air in them they can't pump anything - the air just swirls around the pump gears.  The oil makes the seal in the pump.

Ralph

Date: Thu, 19 May 94 12:37:43 +0200
From: espen@itekiris.kjem.unit.no (Espen Olsen)

>Since motorcycle oil pumps are rotary positive displacement types, they
>should be self-priming. Just remove the sparkplugs and use the kickstarter
>to motor the engine. Or put the bike up on the kickstand in 4th gear and
>rotate the rear tyre. So why bother injecting oil down rocker feed pipes,
>filling the pump with Vaseline, etc?

Well....  My pre-unit Triumph has a "plunger" oil-pump...  Two pistons  pushing the oil. No rotary.

                                 Espen
LA6MGA/LA1K
DoD#7962
Disclaimer?? What disclaimer?

Return to the Contents Page

2.9 Selecting the Right Oils.

Date: 16 Feb 1994 16:37:58 U
From: Marty Ross

Oops... I guess I thought you were talking about the gearbox. My error. Haynes actually recommends multigrade (10-30 in the winter, 20-50 in the summer) for the primary system. I would think that despite all of the great lubrication and hydraulic properties of ATF to support all of the neat gizmos in an automatic transmission, it would break down rapidly when exposed to the high combustion temperature.

Although I must admit that I've never trusted Haynes... I recall that they recommended 20-50W for the transmission of my Fiat Spider 2000. The actual shop manual recommended 80-90W. I never figured out if the haynes was wrong or if their engineers found that a lighter oil was better in that transmission. The tranny in that car was ok for as long as I had it, except for that one time when the gear shift lever pulled out of the transmission while I was crossing the Throgs Neck Bridge (NYC) at 1 am. I thought it was pretty funny, my girlfriend didn't.

Date: Wed, 16 Feb 94 16:00:52 -0700
From: Andrew Wolf

Marty writes: Andrew, I saw your note about using ATF in your triumph instead of 90W gear oil. I know that Haynes recommends the 90W, isn't ATF pretty thin stuff?

Well Marty, that is the point, thinner is better, I don't remember Haynes recommending 90W in the primary (gearbox yes, but that is another chapter). I once made the mistake of putting 90W in the primary and, I could NOT break the clutch free. The local Triumph shop had quite a long laugh and recommened 30W engine oil. Worked better but the line between dragging and slipping was very fine.

ATF may be thin, but it has very good lubricating properties, Think about the requirements in an automatic transmission, Gears, sometimes chains, clutch packs, hydraulic systems. and a well built one will go 100,000 miles So I think that ATF is pretty good stuff.

Date: Thu, 17 Feb 94 09:46:18 GMT
From: Peter Aslan

Thought I'd post this just incase someone started pouring ATF into their engine. I dont know enough about all British bikes to say catagorically (sp?) but the assumption on this thred is that the Primary Chaincase is seperate from the Engine, that is, it contains its own Oil that does not circulate around the Engine. (Not by design anyhow).

Automatic Transmission Fluid provides perhapse the thinist possible oil available which helps the Clutches in the Primary Chaincases work without Dragging or Sliping. However, this oil is Totally unsuitable for use in the actual Engine.

Date: Thu, 17 Feb 1994 08:19:06 -0600 (CST)
From: Jeff Achenbach

>Thought I'd post this just incase someone started pouring ATF into their engine.
>I dont know enough about all British bikes to say catagorically (sp?) but the
>assumption on this thred is that the Primary Chaincase is seperate from the Engine,
>that is, it contains its own Oil that does not circulate around the Engine. (Not by
>design anyhow).

>Automatic Transmission Fluid provides perhapse the thinist possible oil available
>which helps the Clutches in the Primary Chaincases work without Dragging or
>Sliping. However, this oil is Totally unsuitable for use in the actual Engine.

A valid point, at least for later model Triumphs, which have three very small holes to allow engine breathing into the primary, hence also allow some oil exchange. I've been wondering about this since this thread started. Especially when talk got around to intentionally oiling the clutch plates.

If you look at the placement of the level holes on either a BSA, Norton, or Triumph primary, you'll find that with the correct oil level only the chain should be lubricated. In fact, oily plates will stick together something awful, as anyone who has experienced wet sumping on later models of BSA or Triumph can attest.

The design of the clutch basket appears to be such that most of the oil in the primary will be kept out of the clutch. My local shop owner, Jim Stovall, who has been dealing Brit bikes since the 50's, once told me that the clutches are actually meant to be run dry, and that the oil in the primary is really there to benefit chain and sprockets. Makes sense to me. Especially after having busted first gear in the Lightning due to too much oil (wet sumping) crossing over into my primary case.

Return to the Contents Page

2.9.1 Multi-Grade Oils.

Date: Sat, 9 Apr 94 10:58:06 PDT
From: "Pete Snidal" 

Hmmmm. Looks like time for another pontification. This time, I want to share a rave with those of you who can pay attention about: MULTI-GRADE-OILS:

True Story: Long ago, in days of yore (winter of '67 or close), I was a student at UBC, working on finishing off a degree in Industrial Education. (These were the days when there were still a few people in the education system giving at least a little lip service to the concept of teaching kids a few useful skills like determining which end of the hammer to move things with, what's a hammerfore, etc.) Wellsir. One of our courses was called Materials Science, and it was a Doozie. It involved our using a laboratory that had every kind of testing machine you can imagine in it - tensile strength pullers, rockwell hardness testers, viscosimeters.............SNNNNNK! huh? oh yes, ummmmmmmm...... So, it seems that one of the major ways to get through this course was to do a Research Project. You could do it singly or in pairs, and the idea was to dream up a plan to test and compare some kind of material or other.

So we had people mixing up tablets of concrete, varying everything they could think of, then testing all the samples, making charts, graphs, you name it, and then doing a bang-up presentation to the rest of the group.... Side Trip: This same winter was the one when I discovered Castrol GTX Multigrade 10W30. What a Concept! Oil that starts out thin when cold, so it gets in all those tight little places, and gets thicker as the engine warms up! Mirabile Dictu! - why din' _I_ think of that? Needless to say, as soon as I heard of this miracle juice, I ran out and got some for my aging 544 Volvo, and Got With The Programme.

Why Castrol? Some of my less-enlightened classmates in the Auto shop seemed wont to tease me about my yuppieoid taste in lubricants. They snickered out such remarks as, "ever heard of a Castrol Oil Refinery? Ever hear of a Castrol Oil Tanker? Why don't you just use Allstate?", and like that. But I was true. I knew that I'd seen Castrol signs at _ALL_ the big races, and that just _everybody_ used it. Besides, I just _loved_ the lovely BRG cans the regular Castrol came in, and it was a brand that seemed to be mentioned in all the brit shop manuals, yet we could buy it here. Unlike, say Duckham's, which I yearned to put in something someday. It just_sounded_ SO _British_!

You will gather, and, I imagine, Understand, I was a bit of a mechanical Anglophile in them days, and anything Brit was just _too_ cool. If Texaco, or Exxon, ('scuse me-Esso), or Shell, had told me they had figured out a way to make oil get thicker when it gets hotter, I would have called bullshit, but (stand to attention, hand over heart) _Castrol_ - mother's milk for motors, nectar of the gods, the Glen Fiddich of Film Maintainers, the Haig and Haig of Hot Spots - no way! I'd defend _these_ guys to the grave! Well. Back to Materials Testing 405. This being an upper-year course, some of us were taking ourselves quite seriously and going for the gusto with this thing. I can't even remember what your humble correspondent did to slough his way through this assignment, going for the customary 52% +/-2, as this looked like it could be a real time-consumer. But what I _do_remember is the cute couple who decided to go overboard and do a viscosity check on Every Motor Oil In The World.

Now, my friends and I had been doing viscosity checks for some years. How we did it was to run up to the ski area on Mt. Seymour, as fast as our MGA's, Triumphs, and even one AC Bristol (s) would go. We would watch the oil pressure fall as the altitude rose, and compare results. After a summer or two of the Mt. Seymour GP, run singly and in various sub-groupings, and a couple of years of routine oil changes, we were pretty well unanimous in our findings:

1) Fresh Oil changes make no difference to pressure drops as things get hot.

2) The best oil at the time for keeping its act together was Shell X-100.

The only other one that came close was Woodward's Premium. (Woodward's was a local Department Store Chain in Vancouver) As noone had been able to verify sightings of either Woodward's oil tankers, or Woodward's refineries, this latter observation gave rise to speculation that Woody was repackaging X-100. It should be said here that the climb started after about a half hour of city driving, and lasted only for about 15 minutes at full tilt.

So this was not a long work-out, but it _was_ intense - lots of full throttle activity, and lots of r's. How does all this relate to Materials Testing 405? Well, this was the original seat-of-the-pants way to test one material with which we had an interest, motor oil. But of course, my colleagues in the testing lab had a more scientific, if considerably less exciting, way to do it. I mentioned earlier, I think, that these guys intended to squeak every possible mark from teacher for their efforts, here. So they spared no difficulty. They holed up in the materials testing lab for a couple of months, and they wrote friends all over the world, and had said friends send them a quart of oil from places I'd never heard of.

Yes, they had Duckham's. They had Castrol from Aus, from Eng, and the local vintage. They had, in short, Many Kinds of oil. And what they did with samples of every one was run it through a viscosity index test. Starting at 0 C., and running it in 10 (or was it even 5?) degree increments up to well over H2O boiling - 120 C or so. They of course made a careful table of viscosity index at each step for each make _and_grade_ of oil - 5wt, 10wt, 20wt, 30wt, and each of the Multi-Grades.

Data? Did they have Data? They were _Smothered_ in Data! Of course, to make sense of all this data, they had to graph it out, but they had so many brands and grades of oil it wouldn't fit on just one graph. The hand-outs they gave each class member along with their presentation would have cost them a bundle, if this had been in the days of Xerox for the masses. It wasn't, though, so they just made their copy available for all to peruse.

Charts, slides, overhead projector stuff was in abundance, and there was no doubt in _anyone's_ mind that _these_were the ne plus ultra, the champions of brown-nose, the winners of the contest to see who could pull the most marks out of _this_ assignment! I mean, it was Done To The Nuts! I had no doubt whatever that these guys had found out Once and For All what is what with viscosity and heat. I imagine those who have managed to keep the finger off the "n" key up to now will be wondering what they found out. I remember I personally was waiting at the time to find out just how well my favourite new magic multi motor oil stacked up. How much thicker did it get? Did it start out at SAE15, and go to SAE40 when hot, or did it actually get thicker than that, and go to, say SAE45?

Well, as my cousin Vinnie likes to say, "Get ready for a %#$@^^& suhprize." _NO_ multi-grade oil got thicker with temperature. In fact, they all got thinner. In fact, most of them lost viscosity worse than their straight grade counterparts.

Needless to say, no straight grade got thicker either. It turned out that oil, amazingly enough, gets thinner as it gets hotter. I know that I've read claims to the contrary on many an oilcan, but, sorry, kids, that's just how it is. My personal theory is that the oil companies, in trying to find a use for some fractional distillate(s) that wouldn't fit into any normal SAEny category, hit upon the concept of *Multigrade*, as in "We can't really figure out what grade this shit is, maybe You can." Sort of like when some chemist noticed that this stuff they had lots of but couldn't find a use for tasted a bit like orange juice, kinda. Hey! Toss in a couple of astronaut commercials, a bit of good ol' 'Murcan hype, and Presto! You know the rest.

At any rate, ever since, I've gone back to straight grade oil. Since I haven't had a car with a good oil pressure gauge, nor a shot at that lovely little mountain road up the side of Seymour, nor the inclination to drive like that (how nobody died i'll neverknow) I have resorted to common sense in my choice of oils, and I use just a good quality straight 40 in everything in summer, and 10/30 in winter, 'cause I live in a small town, and I don't drive very far in winter.

My Triumphs, my Lincoln, my '64 283 Chev, and my Morris Minor get RPM Delo 40, 'cause there's lots around (logging town), and besides, I've seen Chevron refineries. And what the hay - blue's a nice colour, too!

Date: Sun, 10 Apr 1994 15:21:31 -0700 (PDT)
From: Steve Moseley 

I don't think multi-grade oil was ever claimed to get thicker as it warmed up.

Rather 15W-50 is supposed to be the viscosity of 15 weight oil when it is cold, and the viscosity of 50 weight when it is hot. Cold 15 weight oil is more viscous that hot 50 weight oil.

The thing is, cold 15 weight oil is a lot less viscous than cold 50 weight oil, which is why the multigrade oils are supposedly better in the cold. I use Mobil 1 in my Commando. Anyone know any reason why I shouldn't do this? Date:

Mon, 11 Apr 1994 11:20:41 -0800
From: alastair@cadence.com (Alastair Young)

My workshop manual recommends Esso 50 in summer, Esso 40 in winter.

Straight oils for roller big ends and gauze strainers, particularly with iron heads. 120C is cool..... Multigrades for shell bearings and paper oil filters and high capacity oil pumps.

Date: Mon, 11 Apr 1994 16:54:06 -0700 (PDT)
From: Nancy J Caputo 

On Mon, 11 Apr 1994 brit-iron@indiana.edu wrote
> I don't think multi-grade oil was ever claimed to get thicker as it
> warmed up. Rather 15W-50 is supposed to be the viscosity of 15 weight oil
> when it is cold, and the viscosity of 50 weight when it is hot. Cold 15
> weight oil is more viscous that hot 50 weight oil. The thing is, cold 15
> weight oil is a lot less viscous than cold 50 weight oil, which is why
> the multigrade oils are supposedly better in the cold.

That's my understanding of the way it works too.

> I use Mobil 1 in my Commando. Anyone know any reason why I shouldn't do this?

Steve I tried the Spectro Gold 4+ (whatever the designation-- it's a straight synthetic) in my Ducati and a Beemer and I could swear I had increased leaking. I switched back to Castrol for both. My Commando is actually leakfree except for long high speed runs when I get weeping from the rocker box covers, one of the oil lines and a few odd spots and I'd like to keep it that way.

But the testing on Mobil 1 certainly has been impressive and I may give it a try too. It's not so easy to find however; I tried two auto shops last week with no luck. Someone said that Mobil pulled out of CA and so it's been harder to find the oil. Is this true?

Date: Tue, 12 Apr 1994 08:29:42 +0800
From: jamieh@uniwa.uwa.edu.au (Jamie Hamilton)

>On Mon, 11 Apr 1994 brit-iron@indiana.edu wrote
>> I don't think multi-grade oil was ever claimed to get thicker as it
>> warmed up. Rather 15W-50 is supposed to be the viscosity of 15 weight oil
>> when it is cold, and the viscosity of 50 weight when it is hot. Cold 15
>> weight oil is more viscous that hot 50 weight oil. The thing is, cold 15
>> weight oil is a lot less viscous than cold 50 weight oil, which is why
>> the multigrade oils are supposedly better in the cold.

That's my understanding of the way it works too.

Given the above I run my T140 on a Castrol oil thats marketed as GP50 in Australia I'm pretty sure its 20/50. I live in a warm/hot climate and have put an oil cooler on the bike. Should I consider another oil? Its the one my Brit specialist shop recommends. (I also use it in my V8 Rover and what the similarity between the 2 engines is - I have no idea)

Date: Mon, 11 Apr 1994 17:41:41 -0800
From: alastair@cadence.com (Alastair Young)

At 8:29 AM 4/12/94 +0800, Jamie Hamilton wrote:
>>On Mon, 11 Apr 1994 brit-iron@indiana.edu wrote
>>> I don't think multi-grade oil was ever claimed to get thicker as it
>>> warmed up. Rather 15W-50 is supposed to be the viscosity of 15 weight oil
>>> when it is cold, and the viscosity of 50 weight when it is hot. Cold 15
>>> weight oil is more viscous that hot 50 weight oil. The thing is, cold 15
>>> weight oil is a lot less viscous than cold 50 weight oil, which is why
>>> the multigrade oils are supposedly better in the cold.
>>>

>>That's my understanding of the way it works too.
>>Given the above
>>I run my T140 on a Castrol oil thats marketed as GP50 in Australia I'm
>>pretty sure its 20/50. I live in a warm/hot climate and have put an oil
>>cooler on the bike. Should I consider another oil? Its the one my Brit
>>specialist shop recommends. (I also use it in my V8 Rover and what the
>>similarity between the 2 engines is - I have no idea)

I used GP50 a couple of times. I though it was 50W monograde. It says it on the can somewhere.

Date: Mon, 11 Apr 94 17:43:58 PDT
From: John Bria 

> I tried the Spectro Gold 4+ (whatever the designation-- it's a straight
> synthetic) in my Ducati and a Beemer and I could swear I had increased
> leaking.

I had the same experience quite a few years ago when I tried synthetic oil in my R75/5. Although I didn't appreciate it at the time ( not yet Briticized ), the Beemer began to take on some British traits. Went back to "normal" oil and never needed the remainder of that box of cat litter until I got a "real" British bike.

Date: Tue, 12 Apr 94 09:54:10 -0600
From: Your Name Here 

It is very interesting the reocurrence of oil debates on the net. As stated before, I used to work for Cummins Engine company and the inner sanctum determined the dead dinosaurs were just that. The differentiation is in the additives. Of course we are talking dead dinosaurs here.

Oil does its job by separating the journal from the bushing with a film that usually prevents contact. Any fluid could fulfill this duty, but oil has a high film strength. The major job of the oil pump is to provide cool (relative here) oil to replace the rapidly heating oil in the bearing. In fact if a fluid would maintain its film strength and not boil away (assuming the bearing was rated at a high enough temp you would not need a fluid pump).

The additives can slightly modify boiling point and film strength, but not much. The most important thing one can do is to keep clean oil in an engine. this means frequent oil changes and to me that means the cheapest dead dinosaurs available. (usually never more than $0.70 a quart.

I know that some folks get passionate about a brand of oil and stick to it, but as stated before the additives are the differentiator and these additives are usually out to lunch at 2k miles.

So cheap oil and frequent changes are the secret.

Date: Tue, 12 Apr 94 8:35:33 PST
From: Graeme Harrison 

Andrew Wolf:
>I know that some folks get passionate about a brand of oil and stick to it, but as
>stated before the additives are the differentiator and these additives are usually out to
>lunch at 2k miles. So cheap oil and frequent changes are the secret.

Especially if the bike isn't equipped with an oil filter otherwise the SOP is 3K btw changes.

None of my Triumphs had an oil filter, just a screen. In fact, I can't recall any Britbikes using oil filters unless they were aftermarket products. Kendall 20/50 oil was my passion. :-)

Date: Tue, 12 Apr 94 09:41:34 PDT
From: DHAMLET@MFOR01.FOR.GOV.BC.CA

Andrew Wolf sez:
> The most important thing one can do is to keep clean oil in an engine. this means
>frequent oil changes and to me that means the cheapest dead dinosaurs available.
>(usually never more than $0.70 a quart.

Andrew, I agree more or less with what you say. Bikes are expensive. Very small but critical parts like bushings and bearings require the very best in terms of clean, high quality products to allow them to do their job.

Bikes are expensive, oil is cheap, cheap, cheap. I read the manuals on the new bikes and they suggest oil changes at incredible mileages. Maybe yes, maybe no. My philosophy is on a modern bike say an R100 GS is to change the oil every thousand miles and the filter every other oil change.

For my vintage machines (no filter) I change the oil every 800-1000 miles. Four litres of Castrol 20x50 costs about $7.50.

That's about a pint and a half of beer in the pub. Pretty cheap maintenance if you ask me.

In an old Beemer, for example the oil get thrown about by a couple of perverse contraptions called slingers. Dirty oil tends to get clogged up there and prevents them from doing their job. Result, reduced oil flow, and eventual bye-bye crankshaft. (very hard to replace these days).

I'll stick to the frequent oil change model myself. As for cheap oil---you'll have to do some convincing here. There are a number of studies which seem to show that there is some differences between oils in their ability to maintain viscosity under various circumstances. Most of those studies seem to indicate that within reason you get what you pay for. Any comments?

Derek

Date: Tue, 12 Apr 94 12:00:46 CDT
From: kichline@mpd.tandem.com (Chuck Kichline)

Somewhere out there there's BOUND to be someone who knows what he's talking about - but until then here's my $.02 qualified only by "what my Daddy told me at his knee" (Dad was a Production Chemist for Texaco) and other experiences, as well as general modification of fact by the passage of time.

There are two types of oils. Blended and Vacuum refined.

Most oils are blended, Pennsylvanian oils for instance are very light oils and are blended with heavier "bunker" oils to make the rating. Saconey (don't know how to spell it) Oil Company created vacuum refining - which taped the oil out of the refining process at the right weight. Mobil bought Saconey (remember Saconey-Mobil?) and their better oil (and Texaco Havoline) are vacuum refined.

Experience: Had a buddy who liked to pull a BIG BOAT down to South Padre Island from here at HIGH SPEEDS with his HOTROD. He confirmed that Havoline was the only oil he found that kept oil pressure up after 90mph runs across the King Ranch in the middle of summer. Also knew a Harley rider who commented on his oil tank having a foam head just like beer after using Penzoil for a long ride. I believe I remember Dad commenting on how multigrade oils worked - their molecules curled up has they were heated, therefore the product did not thin out as rapidly as single weight oils. This gives the effect of "thin" oil when cold and "thicker" oil when hot. I remember that he said that the multiweight were never really quite as "thick" as single weight ones.

Roller and ball bearings need different oiling than shell bearings. Shell bearings ride on a "sea" of oil, and thinner oils and high pressures make them work. Roller berings - like the crank and rod bearings in my Indian need a dribble of oil to keep going, and THICK IS GOOD.

The Indian oil pumps through '47 were really just a screw gear metering gravity flow from the oil tank. Maybe too thick oil is why the off side crank bushings go out on the BSA A65's? My '49 Chevy doesn't even have an oil filter. I was going to add one when I was a kid and pop suggested that instead I invest the money in changing the oil as often as possible - you can buy a lot of oil for the cost of a filter. He suggested every 3000 miles.

Date: Tue, 12 Apr 1994 11:15:29 -0700
From: rdb@strata.com (Robert D. Burget)

Graham wrote:
> None of my Triumphs had an oil filter, just a screen. In fact, I can't recall any
>Britbikes using oil filters unless they were aftermarket products.

Tridents and Rocket 3's have a lovely disposable paper cartridge filter hidden under the engine, as well as the traditional sump screen. They are easy to overlook. I too am now a believer in frequent oil changes.I try to do it when the odometer reaches a multiple of 2000 miles.

Date: Tue, 12 Apr 94 13:08:43 CDT
From: unisql!brg@cs.utexas.edu (Bruce Graham)

From Graeme:
>Especially if the bike isn't equipped with an oil filter otherwise the SOP is 3K btw
>changes. None of my Triumphs had an oil filter, just a screen. In fact, I can't recall
>any Britbikes using oil filters unless they were aftermarket products. Kendall 20/50
>oil was my passion. :-)

Tsk, tsk, how soon they forget the Norton Commando. Hey! that would have been a great trivia question...

Date: Tue, 12 Apr 94 12:33:00 -0600
From: Your Name Here 

Andrew Wolf sez:
>>The most important thing one can do is to keep clean oil in an engine. this means
>>frequent oil changes and to me that means the cheapest dead dinosaurs available.
>>(usually never more than $0.70 a quart.

Derek replies:
>Andrew, I agree more or less with what you say. Bikes are expensive. Very small but
>critical parts like bushings and bearings require the very best in terms of clean, high
>quality products to allow them to do their job. Bikes are expensive, oil is cheap,
>cheap, cheap. I read the manuals on the new bikes and they suggest oil changes at
>incredible mileages. Maybe yes, maybe no. My philosophy is on a modern bike say
>an R100 GS is to change the oil every thousand miles and the filter every other
>oil change. For my vintage machines (no filter) I change the oil every 800-100 miles.
>Four litres of Castrol 20x50 costs about $7.50. That's about a pint and a half of beer
>in the pub. Pretty cheap maintenance if you ask me.
>In an old Beemer, for example the oil get thrown about by a couple of perverse
>contraptions called slingers. Dirty oil tends to get clogged up there and prevents
>them from doing their job. Result, reduced oil flow, and eventual bye-bye crankshaft.
>(very hard to replace these days). I'll stick to the frequent oil change model myself.
>As for cheap oil---you'll have to do some convincing here. There are a number of
>studies which seem to show that there is some differences between oils in their ability
>to maintain viscosity under various circumstances. Most of those studies seem to
>indicate that within reason you get what you pay for. Any comments?

>Derek

Well Derek, as you may have noticed, the differentiator is additives. Now certain additives hold particles in suspension (detergents), others modify viscosity (STP), others counteract the effects of combustion by products (acids, water, etc.), and others just for the hell of it.

I do NOT run my engines HARD, yes I live in the desert, but I do not overheat my engines by running VERY fast or under hard load. Basically I am your middle of the road rider/driver. I don't need all of those wonderful properties that the oil resellers provide, besides that every study done on additives show that for a 4 quart sump that the additives in a sound engine are consumed in < 2,000 Miles.

Since I change my oil at 1,500 mile intervals, no matter how cheap the oil it still has the basic additive package available. So I tend not to believe in using oil for great distances >5,000 miles between changes, I also have seen "studies" on oil, however all have been in Auto and Motorcycle magazines and after taking a critical look at thier 'impartiality' I seriously doubt the whores who write for these magazines and take thier income from advertizing these same products.

An interesting aside. Several friends who run Mobil one beleive that they can really get 25,000 miles per oil change!!!! For one this meant 3 years of low milage driving. When the engine was torn down we found much evidence to suggest the damage was done by corrosion. But talking oil does arouse some real passions and it is cheap enough, so no matter the cost of the oil it is still CHEAP insurance.

Date: Tue, 12 Apr 94 14:28:10 CDT
From: clem@romulus.cray.com (Terry Drehmel {x68282 CF/ENG})

Can't agree more with Andrew Wolf and others.

After pulling the crankshaft plug on the Daytona, I found a group of sludge and spooge in the crank passage. More than enough to frighten the daylights out of me. How'd oil get through?

As oil filters go, the crank is a tough one to clean. I have the habit of changing oil every month - a little extreme perhaps, but it's easy to remember and having ridden without a speedo for years, made it easier than rough guesses. I love my Tiger and figure whatever the cost of oil, a rebuild is more costly. Besides, I get more Castrol hats and patches that way....

Date: 12 Apr 94 15:59:00 EDT
From: roddy@diana.dt.navy.mil

Since I have yet to get the Gold Star I am yearning for I don't have any recent experience with multi-grade oils in an old Brit. Bike. I do however, have a 1953 Riley RMF and I have some expeerience with it. The engine has NOT been rebuilt since I bought the car (1971) but it runs well.

With single grade oil the oil pressure would go down to almost nothing at an idle after the engine got hot in the summertime. I ended up going to Castrol 20w-50 and now even at an idle I have about 15-20psi and as soon as the engine is speeded-up the oil pressure goes up and stays up at very close to the spec. in the manual (Since I seem to be suffering from CRS at the moment I can't remember exactly what pressure that is :-) )

The bottom line is that this oil has served me well in my old Riley and if I had a similar problem in an old Brit Bike I think I would try the same solution.

Date: Wed, 13 Apr 94 05:06:48 EDT
From: bman1@aol.com

All this discussion on oil seems to have left out the rather significant technological advance of *Synthetic Oils*. Now I dont claim to be any kind of expert, and the only oil advice my daddy ever gave me was that it doesn't wash out of the living room rug, so I better take those damn boots off before I go walking through HIS house... BUT, I do work in a cycle shop and i have tried to do a little amateur investigations on the matter of synthetic oils.

One of the benefits of British Machinery is that the primary drive is often isolated from the engine oil; thus the main problem that most motorcycles have with synthetics is avoided: clutch malfunction. The question than becomes purely a matter of viscosity and thermal conductivity, and here there is NO doubt: almost any automotive synthetic oil retains its viscosity longer than any petroleum based oil, whether its made especially for motorcycles or not (Spectro 4 for example).

I have read two independant studies that concluded this so I at least am convinced. My boss at work however continues to stock and use Golden Spectro and Spectro 4 almost exclusively and he tells me that there's more to oil than viscosity breakdown - but aside from cleaning additives and such I have no idea what he's talking about. I ran Mobil 1 synthetic in my Norton and noticed that the bike seemed to like me a little bit better for it... until she threw a rod that is. (just kidding)

Date: Wed, 13 Apr 94 14:23:42 EDT
From: John Pinkham 

>From Chevron USA catalog: "Chevron will pay for *any* engine damage directly
>caused by a deficiency in DELO 400 PLUS Motor Oil, when the engine is used under
>normal operating conditions."

This oil is rated API CE,CD,CD-II/SG and passes all the Cummins,Catepillar,Mack, and Detroit-Diesel performance tests. Available in 15W-40 for about $12.50 / 12 quarts. Also meets Porsche,Mercedes,Jaguar, and a long list of US, European, and Japanese manufacturers' specs. I use it in my Ford diesel with close to 400,000 miles on original engine. Chevron Lube-Tek Hot Line: 1-800-582-3835.

Date: Fri, 15 Apr 94 16:54 EDT
From: mason@ftp.com (Latte' Jed)

>I know that some folks get passionate about a brand of oil and stick to it, but as
>stated before the additives are the differentiator and these additives are usually out to
>lunch at 2k miles. So cheap oil and frequent changes are the secret.

I've never been passionate about a brand of oil, but I am a fan of synthetics. The theory is there is less high temperature breakdown, and I do thrash my bikes, so I figure the extra cost compared to what I pay for parts for some of my shitboxes isn't that much of a burden.

But I definately agree, change early change often, change the oil as often as humanly possible and the engine will last forever.

Date: Fri, 15 Apr 94 16:58 EDT
From: mason@ftp.com (Latte' Jed)

>Four litres of Castrol 20x50 costs about $7.50. That's about a pint and a half of beer
>in the pub. Pretty cheap maintenance if you ask me.

Well, I didn't realize good Castrol was so cheap. I guess I'll switch from Guiness to Castrol in the beeza.

Date: 15 Apr 1994 16:41:25 U
From: "Marty Ross" 

Wow, everyone seems to be praising the multigrades. I think my partiality to multi-grades was always the recommended lubricant data chart in Haynes manuals which wave the Castrol GTX banner and not anything technical. However, I did read an interesting technical blurb on wreck.autos.vw that discussed the comparison of multigrades and straight weights.

The bottom line was that a 10W-50 multigrade was simply a 10 weight oil with a bunch of polymers dumped into it so that the oil would artificially thicken to a 50 weight when it got hot. These hooligan polymers will tend to write graffiti on your cylinder walls and look up your piston skirts on the upstroke.

Seriously, It doesn't make sense that a hot 10W-50 would have as favorable tribological (is that a word?), heat transfer, and cleaning properties as a straight 50. The author recommend using straight when temperature variations are relatively low (which is practically nowhere in the US), and minimizing the spread of the multigrade when larger temperature variations are expected and a multigrade must be used (for cold cranking).

I know I've heard a lot about people running castrol multigrade for beaucoup miles, but I have a feeling that they are just meticulous about frequent changes and preventative maintenance... one may be able to stretch engine life even farther by keeping multigrade use to a minimum.

Date: Sat, 16 Apr 94 08:44:04 PDT
From: "Pete Snidal" 

On frequent Oil changes: I read a story in (I think) Car And Driver many years ago reporting on a paper some engineer at Ford wrote up for the SAE. Seems he noticed a correlation between test-engine blow-ups and fresh oil changes, looked into it, and sho' 'nuff......... Postulated that oil needs a break-in period, and the conclusion was that if you're at a racing event, and there's free oil being offered by some maker or another, take the oil by all means, but don't change your oil before a race.

Leave the old oil in there when pounding on it; change oil when the immediate future is lighter practice, driving it on the street, like that.

My personal feeling on changes has always been that running an engine cold produces acids and other ugly stuff you can't see, and that the oil gets rid of these when it gets up to temp by evaporation. If you're doing lots of short hauls, you gotta throw that acidy oil away (or maybe just sit it on the stove at 150 F. or so for a few hours?), and replace it with something a little less corrupted. But if you're doing a good haul, where the thing gets to run hot for at least as long every time as it did cold, you can stretch it longer. Either way, I always change when it gets dirty, unless of course it's a diesel - who wants to change their oil every half-hour? Dirty to me means showing any sign of black - usually about 1500 miles on a bike.

Date: Mon, 18 Apr 1994 16:01:12 -0800

At 4:41 PM 4/15/94 +0000, Marty Ross wrote:
>Wow, everyone seems to be praising the multigrades. I think my partiality to multi-
>grades was always the recommended lubricant data chart in Haynes manuals which
>wave the Castrol GTX banner and not anything technical. Not me.
>However, I did read an interesting technical blurb on wreck.autos.vw that
>discussed the comparison of multigrades and straight weights. The bottom
>line was that a 10W-50 multigrade was simply a 10 weight oil with a bunch of
>polymers dumped into it so that the oil would artificially thicken to a 50
>weight when it got hot. These hooligan polymers will tend to write graffiti
>on your cylinder walls and look up your piston skirts on the upstroke.
>Seriously, It doesn't make sense that a hot 10W-50 would have as favorable
>tribological (is that a word?), heat transfer, and cleaning properties as a
>straight 50. Drill a well and pump your own, I say :-)
>The author recommend using straight when temperature variations are
>relatively low (which is practically nowhere in the US), and minimizing the
>spread of the multigrade when larger temperature variations are expected and
>a multigrade must be used (for cold cranking).

I get first kick starting with straight 50W with icicles on the barrel. I think this multigrade-starts-good-when-cold nonsense only applies to those newfangled wet sump engines.

Date:  19 Apr 94 11:05:36 MESZ
From: tsumner@acorn.co.uk (Tony Sumner)

If I use a multigrade in my Thunderbird (iron head) its okay until the engine gets hot. After a decent thrash (50/60 miles or so) the egine sounds like a bag of nails. If I use straight 50 grade it doesn't get anything like so noisy when hot. Maybe multigrades aren't suited to the temperatures/clearances in older engines?

By comparison, the Commando runs okay on 20w50, but the Velo also seems to prefer monograde oil.

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2.11 Wet Sumping.

Date: Thu, 17 Feb 94 17:08:58 GMT
From: Peter Aslan

Just about the first 'getting your hands dirty' thing the proud new Norton Commando owner does, is to check and top-up the Oil in the Oil Tank. The second thing that same owner does, is drive down to the Garage to pick up a new air filter.

You see, if the bike is left standing, oil will slowly drain down from the oil tank, through the oil feed lines and the pump and into the bottom of the crankcase, or sump. So before our new owner rides off into the sunset, he dutifully checks the oil level, finds not-a-drop on the end of the dip stick and proceeds to fill the tank until the level lies exactly half way between the upper and lower marks.

Now, our frendly designers back at Norton were wondering where to put the Oil Tank vent pipe and decided, to reduce emmisions for the US Market, the only place they could vent the fumes was back into the engine through the intake. (Well, the air box is next to the oil tank right.)

The next part of the story is fairly obvious, once the engine starts it emptys the crankcases oil back into the tank, this is a dry sump engine. The oil overflows through the breather into the airbox, and increases the turnover of said local garage.

And thus, the first thing the new owner discovers about the bike is; to read the small blue sticker on the frame next to the oil filler, or to always run the engine before checking the Oil.

There have been numerious owner modifications in pursuit of a fix. The most obvious and often used is to extend the vent pipe so it hangs below the engine, venting into the air or onto the pavement. I have even seen several people put a small tap into the Oil feed, and operate it like the petrol tap. We don't need to dwell on the negitive aspects of this arrangement to long though. Which brings us to the Non Return Valve, a small one-way valve. A Ballbearing held against a seal by a spring which only lets the oil go one way and thus prevents the oil draining down from the tank.

The only thing you can get wrong is to install the thing the wrong way round. Another item available from RGM Motors, at 12 English Pounds. N.B. Mk3 Commandos had a Non return Valve as part of the timing cover, and there's a roumor that if you bring the engine to compression it stops the wet sumping. (Although this may only work with timed breathers).

Date: Fri, 18 Feb 94 8:27:21 PST
From: John Bria

>Peter Aslan wrote:
>N.B. Mk3 Commandos had a Non return Valve as part of the timing cover, and
>there's a roumor that if you bring the engine to compression it stops the wet sumping.
>(Although this may only work with timed breathers).

I have used the technique of bringing the engine to full compression on return to the garage and it has practically eliminated the wet sumping that I used to experience on my MKIIA.

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2.12 Engine Breathers.

Date: Thu, 21 Apr 1994 13:17:01 +0600
From: magnetic@netcom.com (Jonathan Segel)

quote from "Velocette" by Rod Burris: "A piston engine acts as as unintentional air pump. The problem is more acute in a single cylinder engine than in say, a four, where the variation in crankcase volume and therefore pressure, is less (due to some pistons moving upwards and some downwards).

These changes in pressure generally contribute to oil leakage. One solution was to fit fibreglass shields over the mess. * "At first the new engine seemed not to need a more complicated breather system than one leading to the chaincase via mainshaft drillings. However, it was not until the mid-1960s that it was discovered that at certain RPMs crankcase pressure was preventing oil drainage from the cylinder head and rocker box. this in turn contributed to oil leakage especially down the cylinder head studs and possibly affecting carburation.

An alteration had already been made to the cylinder stud nut sealing by then. "A variety of breathers were tried but the system introduced in Oct. 1966..." (you say yours is a 65?) "... consisted of a 1/2" diameter balance hole between the timing chest and the crankcase (behind the cam wheel). An outlet from below the magneto, which can be added by fitting an adaptor into a 1/4" BSP tapped hole, allowed the connection of a 1/2" bore X 21.375" long hose. "the oil tank had a 5/16" tube welded to the top, to accept the hose. Again, this can be fitted or the existing tank breather at the bottom end used. "A 5/16" bore hose X 27.5" long led from the tank to the rear of the machine.

An earlier tank breather had been used to lubriacte the rear chain. "Opinion varies as to the importance of these dimensions. Reg Orpin was not convinced until an incident ocurred at Barcelona. In the early hours of the morning he noticed that an oil mist ws very obvious as it pumped out of the extra long tank breather. The breather acted, he claims, rather like a megaphone and had an extractor effect. Reverting to a shorter hose reduced oil losses by this route. The technical explanation is tied up with resonating air columns." and the manuals all say to check blockage of vent tubes, and of course cleaning the suction filter and the tank filter.

I am taking on the task this week of getting my friend's 69 Venom back on the road (coil ignition model) it's really a simple job, as she broke the kickstart return spring, parked the bike last year and left it in the garage. (and now with Guzzi problems, she is talking of buying a new bike, god forbid. no, dear the boy who kept it running 'til now doesn't come with it.)

I've already done the minor tune-up stuff, carb and such, and have a new return spring in my hot little hands as of this moment. it goes in later today. This bike does not really leak that much oil, but does unfortunately leak gas, uh, petrol, i think the tank needs a fix. Which means new paint, but she claims there is a VW match for Velo blue. *regarding these fibreglass things, i just saw them for the first time in the corner of the garage. yuck.

Date: Thu, 21 Apr 94 16:33:33 CDT
From: clem@romulus.cray.com (Terry Drehmel {x68282 CF/ENG})

While assembling the Daytona motor, I came across reference to the "Timed Breather Assemblies"

There were none on my motor.

Ever, as far as I can tell.

What's the deal?

Date: Thu, 21 Apr 1994 16:48:12 -0500 (EST)
From: Chuck Stringer 

Terry Drehmel {x68282 CF/ENG} writes:
> While assembling the Daytona motor, I came across reference to the "Timed
> Breather Assemblies" There were none on my motor. Ever, as far as I can tell.
> What's the deal?

On the BSA unit twins there is a small rotating disk at the end of the camshaft with two opposing triangular holes like a spice shaker that allows the pressure generated by the two pistons coming down simultaneously to escape. Otherwise the pistons would be constantly compressing and uncompressing the air inside the engine cases. Not only would this be a waste of energy, it could also force oil out at the weakest points.

Date: Thu, 21 Apr 94 18:11 EDT
From: mason@ftp.com (Latte' Jed)

The timed breather on the daytona was driven off the exhaust cam. On the left side of the motor there was a spigot that the breather tube attached to. The breather on those bikes changed pretty rapidly in the late 60's/early 70's, I can never remember which they had when, and our Daytonas are such piles of parts I have trouble finding the breather on the bike when it's in front of me.

Right behind the barrels on the top of the gearbox (sort of) there's one place where a breather might or might not have been, on one of our bikes there's an undrilled casting bump. I think they vented it through the primary on some bikes (actually that might be on the scheme I just described), and on others I think they vented down around the sprocket somewhere.

Date: Fri, 22 Apr 94 08:12:34 CDT
From: kichline@mpd.tandem.com (Chuck Kichline)

Oil Breathers: My GoldWing has a neat feature with the oil breather tube. It loops up over the engine, then terminates in a small (1"x1.5") plastic cylinder behind the engine and lower than the output. Once or twice a year you remove and drain the cylinder, which is usually full of water (condesation from the engine) but without any major oil contamination.

Might just be that a 4 cylinder is better balanced so needs less breathing, but might be an interesting experiment on a twin.

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