Date: Mon, 9 Sep 1996 14:38:07 +0100 (BST)
From: D.J. Walker
> Could anyone tell me the correct way to aneal copper gaskets (e.g.
cylinder
> head gasket), the heating method, temperature, duration, and cooling
etc.
>
> Regards Garry Lawton
No special secrets, Garry.
Copper's behaviour is exactly the opposite of a ferrous metal or alloy,
in this respect. Heat the copper until it glows an even cherry-red colour,
visible in ordinary daylight, and then dunk it straight into cold water.
For a ferrous metal, this would cause hardening and brittleness, but copper
is softened and becomes more flexible after such treatment. Be careful
not to flex the freshly anealed gasket afterwards, since copper quickly
case-hardens
(people with copper pipes running externally on their bikes - such as series A Vincents - such avoid polishing the pipework unecessarily for this reason, as it will lead ultimately to fracturing of the pipes. That's how easy it is to case-harden copper).
If you're using a copper gasket on a bike where flame-ring types were originally used, you might ask yourself why... The need for such head gaskets in circumstances where eyeletted/flamering types blow out in use, usually points to a warped cylinder head. Copper gaskets won't blow, under the same circumstances, but they will fail to provide an effective seal, allowing combustion gases to escape over or under them and cause real damage to the gasket faces. Reface the head/barrel faces and switch back to flame-ring types, if this is the case, that's my opinion, but I am, as always, open to contradiction.
Garry, I assume your bike was designed with such gaskets in mind, so don't for a moment think I'm lecturing yourself_.
Dan
Date: Tue, 10 Sep 1996 08:24:54 -0700 (MST)
From: Charles Falco
On September 9 Dan wrote:
> Be careful not to flex the freshly anealed gasket afterwards,
> since copper quickly case-hardens...
Actually, copper *work*-hardens, not case-hardens. They're two quite different phenomena. When you heat copper to cherry red, the crystallites are able to grow into large grains (easily visible to the naked eye). A copper crystal is intrinsically soft (i.e. readily undergoes plastic deformation), but the grain boundaries in the copper are quite a bit harder (because they resist slip planes). The same is true for some other metals, such as tin and indium. Totally irrelevant factoid: when you bend an annealed rod of tin or indium, you can actually hear the grain boundaries forming--the squeaking sound it makes is known to metallurgists as "the cry of tin."
When you bend copper, new grain boundaries form throughout the metal as the large grains get divided into many smaller ones, and the piece of metal gets "harder" as a result. You can easily experience this for yourself with a coil of copper water tubing. The stuff starts out easy to bend, but gets very hard after reshaping it only a few times. But, heating it to cherry red gets you back to the soft state (quenching in water lets you get back to work quicker but, unlike the tempering required for steels, is completely unnecessary since, once formed, the grains stay the same size until you bend the Cu). If you use Cu lines on your machine, you need to anneal them after shaping or the vibration will quickly cause the now-hard lines to crack (vibration will eventually work harden them anyway, so periodic annealing can become part of the maintenance routine).
This is quite different than those metals (normally ferrous) that case-harden.
Iron with a high carbon (or nitrogen) content is extremely hard, but also
very brittle. You can have the best of both worlds by heating, say, a gear
in a bed of carbon for the right time/temp. The carbon diffuses a short
distance into the steel and reacts with the Fe, resulting in a thin high-carbon-content
skin ("case"), that is very hard and wear-resistant, on a ductile core.
On September 9 melray wrote:
>The main difference between the 650 Triumph and the Beezumps is: the
twin was
>designed at a time when service with tools you could carry was essential,
and
>refined over a 30 year period. The triple was designed by committee
and
>redesigned by beancounters, and didn't survive long enough for ANY
refinement,
>except by racers of course. You can work on a twin, even completely
rebuild it
>with a minimum of hand tools.
I have to disagree with this fairly common mis-perception. Roughly the same number of special tools is required in both cases, which is as to be expected since the engine follows standard Triumph design practice of the time (except for the clutch), with one extra cylinder grafted onto a twin. If you could travel back in time to, say, 1955 with a Trident engine, it would be instantly recognized as a Triumph by any mechanic at the time (in contrast to a Honda 4 engine, which no one would have been able to identify). As for it being designed by a committee, not really any more so than the twins of the time. Sure, the styling of the original machines certainly was farmed out, resulting in the bizarre--although loved by some--Flash Gordon look, as well as the designed-by-committee misconception.
> I wouldn't attempt another triple rebuild without access to
> either;
> 1) a large quantity of engine parts to rummage thru, or
> 2) a full machine shop (My lathe and mill/drill aren't enough)
I'm not sure what you're referring to. I used an arbor press to help reshape some bent brackets; but, then again, would have done the same for a twin. Used my lathe to make a set of turn signal stalks; but would have done the same with a twin. I have to admit I needed to buy three ring compressors, instead of two. Seriously, if you know how to do decent engine work on a twin, you have the skills and knowledge to work on a triple. That, plus Hulk Hogan to help move it around on your workbench, is all that it takes.
On September 10 Rick Dorgan wrote:
>... I am faced with the disassembly and reassembly of both front and
rear
>wheels. I've straightened my kids bicycle wheels before, but I'm wondering
how
>this translates to motorcycles. Is it something that can be done by
a rank
>amature with time and patience or is it better left for the repair
shop?
The Vintage Motorcyclists' Workshop by Radco (Foulis, 1986) devotes ~12 pages to an excellent, detailed description of how to rebuild wheels at home.
On September 9 Derek Matheson wrote:
>...Also, I will be in London this weekend on the way back, may take
train to
>National M'cycle Museum in Birminham on Sunday morning. Anybody know
the
>Sunday hours please? My return flight is 6 pm, so there is a bit of
time.
The train you need departs Euston station and, unless you wake up incredibly early, should get you there at just about the right time for the 10am opening (same hours every day; closed Christmas). The train will drop you off in the center of Birminham, ~5 miles from where you want to be (which is the southeast corner of the intersection of M42 and A45). I'm sure you could make your way close to the vicinity somehow by public transportation, but I don't know what busses you need. Since your time will be short, I'd recommend a taxi. Also, the one time I went there by train I had luggage with me (I was on my way to Scotland), and found the office in the railroad station for checking baggage didn't open until something like 10 or 11, causing me to waste a lot of valuable time. Check your bags at your hotel in London, and pick them up on the way back.
Charles Falco
Date: Wed, 25 Sep 1996 22:57:44 +0000
From: C_SHARPE
To: internet!indiana.edu!brit-iron
In message "Re[2]:Any oil leak tricks..." on 24, Sept. 14:09...
...English wrote
>As for gaskets, the NOC service notes tend to favor flame ring style
gaskets.
>After blowing out one of these on a run, I setteled for solid copper,
and found
>that as long as a small ammount of silicone RTV is applied in the
region of the
>pushrod tunnels, the setup does not blow or leak oil.
What exactly is silicone RTV ? And is the region of the pushrods the most vulner able place for a copper gasket ???? Would you put it just there or any where else?
Will soon be installing a new copper gasket (I too had a flame ring blow) and would like to avoid any future problems if possible.
Matt
Silicone RTV (Room Temperature Vulcanizing) is the silicone gasket cement available in a variety of colours from bike and car accessory shops. The original stuf was orange, and was known as "Orange Gorrila Snot" by bikers in England at the time (70s). I have found the blue or clear varieties to be less obvious.
The reason to put a smear round the pusrod area is of course to prevent oil leaks. You could put a drop round the return hole as well. The copper gasket will seal perfectly well against compression leaks, as long as the head and barrel faces are flat.
It is IMPERITIVE that you do not put large quantities of silicone anywhere on a bike, The unsightliness of the stuff being festooned all over the engine where it is sqeezed out of the joints is dwarfed by the mechanical failiure when the equal ammount of the stuff that is squeezed out on the inside of the joints clogs up vital oil passages.
Copper gaskets can also be re-used by heating them to red heat and quenching in water to anneal the copper.
English.
21.3 Head Gasket Installation.
Date: Fri, 24 May 1996 21:10:26 -0500
From: Art Xanders
>>Nothing worse than causing a rip in the cardboard after you've got
everything
>>else sitting snug! Never really come up with a solution to this,
myself...
>>anyone found a neat way of doing this?
>grrr. Yes, I've had the same experience and head gaskets are not cheap!
>Maybe some type of gasket goo? Especially suspect is the area of the
gasket
>that covers the pushrod tube.
>rick
In the shop we shoot all of our head gaskets with Copper Coat (available at NAPA among other places) before installation. This includes both flame ring types and copper head gaskets.
BTW it is important to anneal copper head gaskets to soften them before you install them. Even new ones. Heat them up to red, then dip them in water. If they develop some scaling, scrape it off before you spray them with Copper Coat.
These steps (along with laying a straight edge on the head surface to check for "true") have cut our instances of blown head gaskets way down from what we were experiencing at one time.
Art X
Xanders Britbikes
Grove City OH
Date: Wed, 25 Sep 1996 11:37:34 +0100 (BST)
From: D.J. Walker
Dear All,
Regarding the fitment of bigger sprockets to Commandos, I tend to agree
with the view that to treat this approach as the cure for engine wear during
high-speed cruising, is something that should be regarded with caution.
I've recently gone back to a 19-tooth sprocket, from a 21-toother, and
it's fair to say I ride fairly agressively (I'm delighted to find I can
now do rolling wheelies whilst travelling downhill, for instance, whilst
power wheelies are performed by giving the bike 2 1/2 thousand revs, dropping
the cutch, and shouting "Airbourne" at the top of your voice).
Switching to a bigger gearbox sprocket is realy only an attempt to compensate for the fact that the Norton should have had a fifth gear, in a stronger box. Taking the stress off the engine by this method simply shifts the strain onto the box: the weak link in the Commando's drive-train. I have a newly-acquired friend here in Leicester... (despite my general obnoxiousness, I still seem to acquire friends, it's very strange)... who has promised to give me a special competition-use engine primary-chain sprocket, which has an Extra tooth over the standard one. I'd be interested in this, since it would appear from first inspection, that the three mounting studs for the alternator stator would prevent the possibility of fitting a bigger sprocket in this location. If it is possible to fit this new sprocket on my bike and keep the alternator, I might give it a go and let you know the results. Personally, I'm dubious.
Of course, a bigger engine sprocket like this, would have been the proper solution for NVT to use. It would have reduced the torque on the clutch, as well, reducing the need for that heavy spring. Although it would have been difficult to adopt a bigger drive sprocket, and still retain the Lucas alternator, it wouldn't have been impossible. An adaptor plate, could have been used, for instance. More significantly, since some British-built machines of the time, such as the export model safari Landrovers, were using Bosch electrics, it would seem that Lucas didn't own the British industry. An alternative alternator could have been sought, but that kind of thought belongs in the "if only" basket, doesn't it?
This old Compression business has got everyone hot, hasn't it? I can't even remember how it started. Someone commented that 10.5:1 isn't an especially high compression ratio, and so what's all the fuss about the Combat motor using such a compression? Well, yes, 10:1 is pretty mild for a bike like an oversquare Jap four, but a long stroke Brit twin is another proposition. The strain on a long conrod, and a big throw crank, in achieving that kind of compression can be enormous. The Commando achieves a lot of its torque, no by some magical property known only to AMC engineers, who appear to have known very little (that's a joke, by the way), but through the tremendous leverage you can get from using a crank with a big throw. Fortunately, the Norton twins always had a more spherical combustion chamber than their Triumph counterparts, so that when set up right, Comabts may have had a tendency to shake themselves appart, they seldom blew holes in the tops of their pistons.
I find the business of using copper head gaskets on Commandos questionable, and I think I've intimated as much, before. If the flame ringer gaskets are blowing, on a standard bike, even a standard Combat, something's wrong with the head/cylinder seal. It's not worth starting a flame war over, however, so that's as much as I'll say.
Another thing about what's been said regarding the "differential heating" of the iron cylinders and alloy head and crank cases, is that the flame-ring head gasket is specially designed to compensate for this fact, because it is treated with a different variation on hylomar gasket-sealing compound on its top, and bottom, faces. The bottom face is treated with a brand of hylomar specially developed for binding to cast iron; the top, with a variety designed for aluminium. That's why you must never, ever, use silicon-based gasket sealers, when fitting a flame ring type gasket - fit them dry, the built-in sealant in the gasket will do a far better job than anything you could butter it up with afterwards. Also, although there's a hole on either side, at the rear of the gasket (implying that you can put it in either way up), these gaskets are labeled pretty clearly, with the word "TOP", on their upper faces, signifying which way up it's supposed to go. The other hole is only there to make sure nothing goes amiss, if the gasket _is_ inadvertantly fitted upside down.
I can re-use a flamering gasket on my 850 as many times as the holes for the studs will last, but that's because I made sure and refaced the head and barrels, and make sure I follow the torque-sequence Les Emery described to me, once (torque all the bolts as in the book, then give the central 1/4Whit-headed cyclethread bolt - that's number 1, in the torque-sequence - an extra 5ft/lbs. This works every time, and I never have a gasket blow on me: and remember, _I'm_ the "Airbourne" man!). Am I bragging? Well, yes, sort of, but there really isn't a need for copper IMHO. "Copper _Gaskets_? This is the 1970s, man!"
It'll probably be said many-a-time, yet, but I'll join the chorus of people advising the guy who's thinking of buying a 2S camshaft to go for either a standard, or a 4S, instead. 2S camshafts are crap.
I'm delighted to see Classic Bike advising some poor sod to keep his HiRider standard, and thereby preserve a part of our cultural hertiage, in their latest issue. It's all very well saying this to someone, but would you say it to _yourself_? Then again, if Harley Davidson made aeroplanes, would you fly in one? No don't answer that, we all know what happens when one of THOSE discussions starts on the list!
I notice Hilary Clinton gave a banquet in honour of Diana Spencer, the other day. Presumably Whitehouse staff are now trying to extract handfulls of partally digested pheasant, asparagus, sauted spuds and eggs-in-herb-sauce, from the toilet in the visitor's suite, even as we speak. Lovely woman, that Diana. Total f*ckin victim!
Dan
Date: Sun, 8 Sep 1996 02:56:38 -0400
From: Mike Taglieri
>>Can't the entire engine come out as a unit? I'd appreciate any words
of
>>wisdom on this topic.
>
>Yes it will come out as a unit, I've done it myself. Best advice,
go to the
>local gym and recruit two weight lifters to help, its one heavy SOB
of a motor.
>
>Removing it as a unit makes it a_lot_easier to get the cylinder head
off. If
>you've never removed a Commando head with the motor in the frame,
take it out
>as a unit, that way you'll know what you're in for when you do try
to take it
>off in the frame.
>
>Ken
It's a piece of cake to get the head on or off a Commando if you use this little trick to keep the pushrods under control. Here's a rerun of a post I sent some time ago. Sorry if most people have seen it, but stories about how hard it is to remove Commando heads keeps getting recycled.
----------------------------------
This problem of installing Norton heads arises because Nortons have their pushrod tunnels permanently cast into the cylinder barrels rather than using the vast array of little tin tubes, rubber washers, etc., found leaking onto older engine designs (the names of which modesty prevents me from mentioning). The Norton design was a major improvement in oil-tightness, but it makes getting the head off and on with the engine in the frame very tricky indeed if you do it the way the book says, because you're supposed to lift all four pushrods as high as possible into the head and hold them there while you lift the head out of the frame, or you won't have enough clearance to get it out. Six hands are the practical minimum for this job, and most Brit-bikers have only two.
The answer is to use a pair of nylon tie wraps (the kind used on electrical harnesses, etc.) As soon as the head is lifted free from the gasket, put one tie wrap around each pair of pushrods, fastening it so the long end of the tie wrap poinst out away from the barrel. Snug them up tight enough so that it's a bit difficult to move them up and down on the pushrods.
Now, as you remove the head, push the tie wrap down all the way on each pair of pushrods, then put a finger from each hand under the tie wrap on the pushrods to hold it up (and its pair of pushrods) as you're lifting the head free of the engine. Holding each pair of pushrods this way leaves you eight fingers to lift the head out of the frame. it will be easy to keep the pushrods snug against the head and you'll clear the frame with no danger of bending a pushrod, and no extra hands needed.
After the head is off, keep the tie wraps on the pushrods (unless you need to service them, of course), so you can tell the left pair from the right pair by the direction that the end of the tie wrap is pointing. To reinstall the head, just hold the pushrods high up in the head with a finger on the tie wrap as you did before while lifting the head loosely onto the barrel. Once the head is past the frame and over the barrel, with the pushrods in their tunnels, you don't need the tie wraps anymore, so snip each one off while HOLDING the long end, to be SURE no nylon bit falls into the engine.
Note that the only purpose of this trick is to keep the pushrods out of harm's way during removal and installation of the head. During installation, you still have to follow the book and be sure the pushrods are properly located on their rocker-arms before tightening down the head bolts, or a pushrod could be bent.
If, like the writer above, you've already taken the head off by the traditional blood & chaos method, you can still put it back on with the tie-wrap method (First make sure the pushrods damaged during removal have been replaced and all skin lacerations have stopped oozing, which could cause rust). You simply have to put a tie wrap on each pair of pushrods, aiming the end of the tie wrap toward the outside of each pair so you'll be able to tell the left from right. (If you've mixed them up already, you'll survive, but it's better practice not to interchange pairs).
I invented this trick many years ago, and used it last October on my ring-job with no problem, even though I was out of practice. Easier head installation is probably the only good thing that can be said about separate pushrod tubes of the earlier engine designs -- this trick makes Norton head removal & installation almost as easy, without giving up the oil-tightness and durability of cast-in pushrod tunnels.
Date: Mon, 27 May 1996 03:23:01 -0400
From: Mike Taglieri
I put my cylinders and barrels on today, using a method that I long suspected might be easier than the traditional way, but had no chance to test until now: I put the pistons in the bore FIRST, then attach them to the rods as I installed the barrel, and I think this is easier.
The last time I did a ring job, I had a hell of a time getting the cylinders down onto the pistons with the ring gaps in the right places, etc., after I'd installed the pistons onto the rods -- pistons flopping around, silicone sealer (for the base-gasket joint) going everywhere. Horrible mess.
This time, the barrel was upside down on my workbench when I put the pistons in the bore. It was easy to get the rings into place, one at a time -- I could even press each section of Norton's notoriously fragile oil-control rings individually into the bore with a probe. Then, at the bike, I propped the barrel over the connecting rods with the bottom of the pistons hanging out of the bores (and the inside circlips already in place), slipped in the wrist pins, installed the outside clips, and tightened the barrel down.
There are a few tricks: I needed a suitable drift to get the rod ends lined up with the wrist-pin holes in the piston [a 3/8" socket extension worked fine]. Also, I kept a hair-dryer handy in case I couldn't get the wrist-pins home, since Norton pistons sometimes require heat, and their suggested method [boiling-water] is absurd.
All in all, I found this much easier than the method recommended in most manuals, and I encourage people to try it. If it doesn't work, you can always pull the pistons out of the bore again and do it the traditional way.
Mike Taglieri
Raul -- '72 Commando Interstate
Date: Mon, 27 May 1996 06:39:30 -0700 (PDT)
From: Bob Bickers
Mike put lots of rags around the rods, if you drop that cerclip all
you
works fo nought. Cheers Bob for nought
Date: Mon, 27 May 1996 08:25:00 -0700 (MST)
From: Charles Falco
On May 27 Mike Taglieri wrote:
> I put my cylinders and barrels on today, using a method that I
> long suspected might be easier than the traditional way, but
> had no chance to test until now: I put the pistons in the bore
> FIRST, then attach them to the rods as I installed the barrel,
> and I think this is easier.
<snip>
> All in all, I found this much easier than the method
> recommended in most manuals, and I encourage people to try it.
> If it doesn't work, you can always pull the pistons out of the
> bore again and do it the traditional way.
Hey Mike, try your method on a Trident. Go ahead; I dare you.
Seriously, though, is there some reason why ring compressors are difficult to use on a Norton? Your technique does sound like it might be a little easier, *if* the wristpins were a slip fit, and *if* you had a friend to help (or a miniature jackstand). Otherwise, supporting the barrel/piston assembly in mid-air while trying to force a reluctant wristpin into place sounds like even more of a headache than, say, installing the barrels on a Trident. What am I missing.
On a completely different topic, a few weeks ago I took mild umbrage when someone made an unflattering reference to "Dr's on Ducati's." I take it all back. This weekend 10 of us on 7 bikes (3 of which were Ducati's) had a wonderful time (note: "wonderful time" = high speeds, twisty roads, nice friends, and no tickets) on a two-day trip riding 600 miles through Arizona and New Mexico. When we got to the motel in northern Arizona on the first day, there already were about 10 bikes--all but two were Ducati's--parked in a cluster on the walkway in front of the rooms at one corner of the motel. Also parked there was a new six-passenger pickup truck attached to a huge flatbed trailer with lots of tie-down points. Not *only* for hauling a number of the bikes up there, mind you, but also to carry the rear stands and bike covers for a couple of the 916's. Wouldn't want the rear tires to get dusty or develop flat spots overnight, now would we? The next morning (Sunday) just before 7am, the jerks started at least three of the bikes to allow them to warm up for the next 30 minutes. Which, of course, also allowed everyone in the motel to share in the wonderful sound of their carbon-fiber mufflers. They took turns warming up bikes, so there were always some running until past 8am. One in a while one would take off down the street, then return a few minutes later. No doubt to sort out the suspension settings. Come to think of it, I don't remember any tire warmers, so perhaps it was to get the tires up to racing temperature. Two of them were in official Carl-Fogerty-lookalike red/white one piece racing leathers with matching helmets and all the correct Ducati logos. Those two spent most of the early morning posing next to their 916's waiting to answer questions posed by the no-doubt admiring and jealous motel clientele as they stumbled out of their rooms. The Fogerty twins did each make at least one run each down the street, so I can personally vouch for the fact they can ride a motorcycle. Maybe the best part was when a group of Harley riders pulled into the restaurant across the street, and they all snickered and smirked at the obvious inferiority of those bikes and riders. What a group of complete, flaming, self-centered, jerks (pardon my language).
In contrast to the Dicks on Ducks, the concept of my group was to ride-as-you-liked (i.e. anywhere from fast, to very fast) to predetermined points ~75 miles away, then stop for long times to regroup and socialize. Average speed for each day was 33 mph (~300 miles in 9 hrs.). By following immediately behind a friend (who is an AHRMA racer) on an identical machine to mine, and debriefing him on technique at every stop, I got a private two-day, 600 mile sportbike riding lesson. Thanks to his tutelage, my riding ability took a significant step up this weekend. It is amazing how far over you can lean a modern sportbike, and still be nowhere near the limits of the tires. By the way, I am cautious by nature, and yet I did nothing that I felt the least bit dangerous ("Sure, kid, tell it to the judge"). The _only_ flaw to an otherwise perfect weekend was running into those Dr.'s on Ducks at the motel.
Charles Falco
Date: Mon, 27 May 1996 12:16:18 -0400
From: Mike Taglieri
In a message dated 96-05-27 11:26:26 EDT, you write:
>Seriously, though, is there some reason why ring compressors are
>difficult to use on a Norton? Your technique does sound like it
>might be a little easier, *if* the wristpins were a slip fit, and
>*if* you had a friend to help (or a miniature jackstand).
>Otherwise, supporting the barrel/piston assembly in mid-air while
>trying to force a reluctant wristpin into place
Actually, you're not holding the barrel "in mid-air," because (at least on Nortons) the barrel fits down onto studs that stick up from the case. You can keep the barrel above the case simply by ensuring a slight misalignment between the studs and the holes in the base flange. I've used ring compressors, but don't find them particularly convenient.
Mike Taglieri
Raul -- '72 Commando Interstate
P.S. Those "Dr's. on Ducks" sound completely quacked. . . .
Date: Mon, 27 May 1996 14:27:40 -0700 (PDT)
From: Eric William Lamberts
AS a new expert on this job, I must say I find the "traditional" way not too onerous. I did this twice last week, having fogotten to install the outboard circlips.
My method was to set up all the ring gaps and then put hose clamps on as ring compressors, tighening them fully. I then install the pistons on the rods, not forgetting the circlips. The pistons are then set on a U shaped piece of wood described in most shop manuals. This holds them in perfect vertical alignment. After loosening the hose clamps about a turn, you'll find that the cylinders slide on with very little trouble; be sure to oil the bores, tho'.
Eric Lamberts
Date: Wed, 5 Jun 96 08:02 PDT
From: Robin Mullett
My 73 suffered the same symptoms of smoking on one side after a complete rebuild, then replacing the pistons again, truing the head, as well as checking the head for cracks and lose guides, still to have the same problem. A friend of mine suggested we put a high temperature silicone{3M 1211} below the insulating washer around each valve just in case there was a small crack.....it FIXED THE PROBLEM. It has been over a 1000 miles since then and it s runs great and does not smoke
21.8 Valve Guides and Lubrication.
Date: Sat, 11 May 1996 09:28:08 GMT+0100
From: Knut Sonsteby
10 May 1996 Tom Allen wrote:
> Thanks for the reply on Matchless valve guide oil supply setting.
I now
> have a question. Why is it that Matchless requires oil fed to the
guide
> while Norton has a seal to keep oil out of the guide? Perhaps I can
extend
> the life of the phosphor bronze guides in my Nortons by nicking the
seal
> so a little oil leaks in? Or eliminating them altogether?
Tom raised the question of why the Norton twin apparently needs less of valve guide lubrication than a Matchless single.
Firstly, this is probably only at first sight. Later Norton engines (from '66 up) had pressurized lubrication of the head, providing at least two effects:
1 - heat is absorbed by the oil and led downwards in large quantities,
2 - oil mist and dedicated jets towards the valve stem and protruding guide ensures continous lubrication, if not even over-lubrication. Norton found this to be a problem and fitted rubber caps over the valve guides on the 850, as did many automakers with their engines - in the case of Norton not to much help. Trouble spot was not inside of guides but outside, i.e., poor preparation of head allowed oil to dripple along the outher surface of guides.
The original guides of the Norton twins were made of cast iron (as on Matchless singles). This material offers a microscopically coarse wearing surface (similar to the cyl. liner) which keeps oil in pockets and lubricates well itself (by free carbon), so-called "emergency lubrication".
On the downside, cast iron has a much lower heat dissipation property than does phosphor bronze, the most common alternative guide material.
I believe some later Commando models (Combat, 850, JPS, ....) used bronze guides, and information I hold shows the F750 was fitted with aluminium bronze guides (p/n 061394, 061395).
Phosphor and aluminum bronze materials are equivalent (the latter being stronger and harder), thermal conductivities are in the range 325 ... 375 W/(m*K) while cast iron has a value of approx. 80 W/(m*K).
The thermal conductivity determines the temperatures that the valve, its stem and the bearing surface will be exposed to at a given heat and dissipation flux. At first sight, and neglecting valve heat dissipation by radiation and transfer to surrounding gas and oil media, one might believe the stem temperature to remain cool at only 1/4 of the temperature of the cast iron guide setup. However, thermal flux through the cylinder limits this advantage. A simple example illustrates this:
Given steady state temperatures
Now back to Tom's question: Why is there a different need of valve guide lubrication when comparing two engines such as the G80CS and the late Dominator?
1) Heat and cooling fluxes through thhe valve and the head casting (via hemisphere) are differing caused by geometry and combustion differences.
2) Guide seating differs. Important here is the contact area (and apparently degree of contact in the case of Norton!)
3) Choice of materials of valve stem and guide.
It is very difficult to quantify the need of lubrication further. John Hudson, the Norton twin expert, suggests running the twin with bronze guides and *omitting* the rubber caps. These caps have a meaning only in connection with cast iron guides, limiting the oil picked up by the reciprocating valve stem.
NOTE: The increased oil supply needed by bronze guides also implies more oil burnt, because the thicker oil film covering the valve stems is being washed off by the fuel/air gas mixture continuosly. So running this setup isn't necessarily a contribution to lower emissions. Fuel injection would improve on this washing effect!
If there is a problem with wear of bronze guides in the Norton twin, I definately would omit the rubber caps & check running clearance. Keeping an eye on oil consumption and doing an exhaust analysis from time to time is for foresight.
A sensible person might after reading the above conclude that the cast iron valve guide setup is worth keeping for normal road usage. Both valve and guide materials are fully capable of sustaining the operating temperatures.
Personally, I feel that the use of bronze guides has become a fashion more than a true need. Few use their bikes for racing, however in this case only I would still advocate it.
Regards,
----------------------------------------------------------------------
Knut Sonsteby
Date: Wed, 9 Oct 1996 21:20:27 +0100 (BST)
From: D.J. Walker
Ken Dubey's having trouble with his Commando...
>Well I finally found my top end noise. That rythmic tapping noise
is the sound
>of the exhaust valve guide bouncing up and down in the cylinder head.....
Looks
>like I'm going to need a new cylinder head, I don't think I can get
a guide to
>stay tight in the now oval hole in the present one.
Rebore the hole (preferably to one of the stock oversizes available) and replace the guide. I think the standard guides go all the way up to +0.015", or something. Les Emery in Staffordshire only ever makes them up to order, anyway, and I'd have thought most of the more reputable dealers would do likewise. The cost of getting a one-off guide made is usually about 15 pounds, maximum - maybe between three to five times the cost of a standard iron guide. Whenever a valve guide starts shifting, it's going to make the hole oval, and the hole's always going to need reboring. If it's the same guide, that's gone, as before, on your bike, Ken, and you didn't rebore the hole before fitting it, that could be the reason it's shifted again, now.
Exhaust guides always seem most prone to shifting like this, not only on Nortons, either. It could be down to the very short pivot of the rocker arm, applying a greater sideways stress on the guide, compared to the long arm and smaller angle of pivot, in the inlets. Whenever you have the valves out, check for, and remove, any signs of dimpling in the top of the valve, where the tappet is snagging as it depresses the valve. This creates extra side-load on the guide, and causes internal wear, and a greater risk of the guide shifting.
It's amazing how little oil-smoke will be generated by a shifting exhaust guide, too, no matter how loose the guide. A lot of the oil gets blown out as liquid, rather than burnt, and gathers in the lower reaches of your exhgaust system. Small droplets of liquid oil ejected from the exhaust are always a sure sign of exhaust guide shift.
Dan