classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: ramwing7 on July 06, 2022, 08:41:30 PM
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I'm putting together a 1973 Triumph T140V Bonneville OIF.
The header pipes seem to just stick into the head without any method of attachment, gaskets, etc. The parts lists I've looked at don't show any gaskets, etc.
What keeps the pipes tight in the head and not leaking profusely?
Thanks.
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What do those big finned devices on the pipes at the ports do ?
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If they're the same as other Triumphs I've worked on in the distant they're essentially decorative...... From (probably defective) memory the pipes are just held in the head by the various brackets - nothing at the head end at all.
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Ohh Ian - for shame Sir. The finned clip whilst not the best works fine enough if POs haven't bodged the thing to death, or mangled the flared end or the exhaust adapter. I would agree though it does not provide much support, it being primarily a sealing clamp. For sure, all fastenings for the rest of the system should therefore be tight (and present!) for that very purpose.
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Good question R. I've often wondered what those big, finned things do, since there's nothing inside the pipes for the clamps to squeeze down on. Maybe they are heat radiators to cool the header pipes?
I still gotta think these things are gonna leak a lot.
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No shame in not knowing much about Meriden twins. Now if I didn't know about Norton singles I'd hang my head......
I still think they serve no useful purpose (the finned rings not Triumph twins). Althoug come to think about it.....
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Crossed purposes here I think. The earlier finned clamps did indeed clamp down on the threaded-into-the-head stub, although weren't the later Meriden Triumphs exhausts push-in rather than push-over? That's from a memory of decades ago so may well be wrong.
Then there was the huge star-shaped exhaust rosettes as beloved by cafe racers and ch*pper builders(?) which merely clamped on the pipe to "allegedly" dissipate heat at the head.
What's wrong with Trumpets anyway? Good spares supply, easy starters, easy to work on and stylish.
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Ramwing
I have a 66 T120 which has the threaded exhaust pipe adapter in the head - E5914 - that Rex possibly alludes to. Exhaust fits over that and the finned clip clamps down over it. It seems the comparable US versions had no flared end at the head of the exhaust and no finned clip - so seems like a push fit inside the head. I think later Bonnies also adopted this push fit, though why you should have a finned clip if that were the case is indeed a little odd. I would agree that sealing may well be an issue. One for a specific forum perhaps?
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Ian
No shame in not knowing much about Meriden twins. Now if I didn't know about Norton singles I'd hang my head......
I still think they serve no useful purpose (the finned rings not Triumph twins). Althoug come to think about it.....
Nowt wrong with Triumph twins. Aesthetically pleasing, relatively simple to work on. Mine handles and goes down the road very well. Very temperamental, petulant and occasionally unforgiving, but still a blast to ride.
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Very temperamental?
Not in my experience. As used to be said, if a Triumph twin didn't start in two kicks get the spanners out..
This is for a standard bike of course. All bets are off if it's been fannied-around with by the local undiscovered Triumph tuning expert..
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To get back to the original question, it's dead simple. Look around other bike designs and you'll find push fit exhaust pipes are surprisingly common. They work well and require only fairly basic trade knowledge to fit.
I believe your Triumph had a crossover pipe close to the head as standard. If you then look at the exhaust system as a whole you'll see that if fitted as per factory with all the correct bracketry, the crossover pipe and Godwot it's just about impossible for the system to blow off. All you have to worry about is some possible leakage around the pipe up inside the exhaust port. It didn't leak when new but who knows what has been done to the beast in the 50 years since.
If there is some leakage this is easily addressed with a reasonably sized ball-pein hammer. One expands the pipe a whisker at the leakage point with the ball end of the hammer, usually just a few thou will do it and tries again. It gets easier with practice.
Nothing fancy is required, costs zero, just skill with a hammer.
Push in exhausts are effortless.
Cheers,
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Something I've used to good effect is exhaust 'cement' or paste.
This is a white paste, that dries rock hard.
(it may have once contained asbestos, but I think thats long gone).
I smear it lightly where pipes push together, or in the port.
Once all assembled and clamped etc, you then start the bike and the heat dries and hardens it.
This makes it near impossible to have exhaust leaks / pops / backfires.
And is not too difficult to remove next time.
Esp useful when pipes may be old and a bit knocked around and perhaps not seal perfectly - otherwise.
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Ordinary bathroom silicone is even easier, cheaper and easier to remove when dismantling. If in direct contact with exhaust it will burn off but will seal push in pipes and silencer joints fine as well as tired asbestos / copper sealing rings. Velo & Norton experience rather than Triumph......
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Yes, they’re the modern way but I was trying to make the point that with trade skills one doesn’t have to rely on keeping various goops and gunks in your workshop but just does it for free with a hammer with no future clean up issues.
Each to his own I suppose.
Cheers,
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As has been said here before those trade skills are often lacking, and most of us are probaly jacks (or jills) of all trades with the well known consequence....
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If you have to apply pein hammer, cement, paste or silicone to prevent the exhaust at the head from leaking, then it's a poor design in my view.
Hence my comment that Triumphs are temperamental beasts. When sorted they are fine enough, but my gearbox is still rubbish.....
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Heck, I've applied some or most of those to bikes cars planes and boats at some point.
What does that say then !
Old machinery rarely conforms to the modern fit-and-forget philosophy.
And throw it away if it doesn't ...
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Then there's the older Japanese method where a large clamp holds the pipe in the head, and is secured by two dinky 6mm MS studs; quick and cheap at the production stage but bloody painful on an old four-pot that's had numerous heat cycles just to make sure those nuts aren't ever going to unscrew again.
Or the very fine threaded port in the head, as with some Nortons and poxy Morini's. Unscrew the gland nut and see half of that fine thread unwind with it, and that's always great for a hearty laugh when that happens.
Nope, I'm OK with the push-in design as used on many other bikes and not just later model Meriden Trumpets. At least it works and carries on working.
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There is a fundamental difference in repairing something - inevitable with old machinery for sure - and fixing something that was a poor design in the first place. Push in exhausts are (to me anyways) poor design, as are pressed steel chaincases with the rubbish band seal, flip up side stands, placing electrics where the bike gets wet etc etc.....
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The fine threaded port on Nortons is fine with a cast iron head - indeed mine was solely responsible for holding the exhaust on for some miles after the silencer bracket - aftermarket item of course - fractured. I admit that it could cause problems on the alloy Commando head but usually because people didn't keep it tight enough.
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Never had any real issue with exhaust headers on the many Jap bikes I have had. Couple of broken studs, but replaced easily enough. Nuts can slacken off slightly, and where that happened I simply lock-nutted it. Personally I think they make for a decent, tight, compression fit with the hollow copper gaskets.