The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: sprint on 31.05. 2014 21:27
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Had the RGS less than a year and with a number of issues to sort out have only done about 1400 miles on it.
Since I first started it, it was bought as a complete full restoration and had not be used on the road, the top end has been very noisy and tappety.
It had a new 357 cam, new followers, seats, guides, valves, springs etc. Anyway, not being happy with it I lifted the head a few weeks ago and found an inlet guided loose (details in previous post) so was convinced that was the problem.
Having now had new guides fitted all round and rebuilt the engine, 25" thou crank play so I had to shim that out as well, I find that it is just as noisy/tappety, well pi---ed off.
All the rocker arms and shafts have been checked and have no play.
A friend has a 57 RR and a 60 SR and I have a couple of unit Triumphs which are so quiet when compared to the RGS which is far more audible over the goldstar silencer and any other engine noise when riding.
Valve clearance are set to the correct 8" and 10" thou (done with the other valve fully open). Does the 357 cam have a particular profile that exhibits more valve tappet noise as beyond that I am at a total loss?
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G'day sprint. They are noisy aren't they? Both mine are (357's in both '51 & '57), the '51 a little quieter as it's an A7 and lower comp. I believe it's due to the 357 not having the same opening and closing ramps as the 356.
Cheers
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The bggest culprit for head noise is of course the valve lash.
The second biggest is axial play along the shaft .
The thakery washers are the culprits.
They are a cheap and nasty way of positioning the rockers over the valves.
Contry to popular belief they are in fact a spring and loose their temper in use so should be replaced whenever the valve springs are done.
If you want to really quiten the head, replace them with thrust washers, ground down to align the rockers. ( long & painfully slow job ).
This is almost SOP for unit single owners.
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Both mine are shimmed Trevor. It did make it a tad better.
Cheers
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That's a bit reassuring, I have a 357 and 67-1126, and I've noticed lately it's a bit noisier than it was on initial mileage, but reset the clearances not too long ago.
Thought maybe the supposedly Dural pushrods may be wearing down (note to self), or as was suggested a while ago in another thread, the cam was ground years ago, and maybe lifters not sitting solid on the cam- can't remember if I double checked that or not...? (another note to self)
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Hi Sprint, yes the alloy heads do tend to be a bit clacky,. I've messed around with tappet clearances, and dressing the end of the valve stems, and replacing the spring washers in the rocker box, but it still sounds the same on my '61 Super Rocket . My '54 Golden Flash with an iron head however, is pretty quiet. Other iron head A10's I've heard are also quieter than the alloy heads. It sounds strange, seeing as they both have alloy rocker boxes.
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They are all like that sir! I just accept it and live with it. Incidentally, a few years ago I owned a Douglas 80 plus. The exhaust valve clearance on that was 25 thou. Now that really did rattle!!
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And Sprint.
If you use it as intended (flat out) you will need to open up the tappet clearance to 10 & 12.
Cheers
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Thanks for all the replies and comments.
It's reassuring that it would seem to be just part of it's 'natural charm'?
Rocker shims and Thackeray washers are OK and since most bikes of that period use the same set-up without them all being very 'tappety' it must be part of it's characteristic and possibly due to the 357 cam?
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Thanks for all the replies and comments.
It's reassuring that it would seem to be just part of it's 'natural charm'?
Rocker shims and Thackeray washers are OK and since most bikes of that period use the same set-up without them all being very 'tappety' it must be part of it's characteristic and possibly due to the 357 cam?
One thing a lot of the RGS engine guys are doing , is replacing the tube, (or black hose) at the top of the rocker box, down to the normal flex between the two, with a clear hose, so you can tell if the rockers are getting properly oiled. Less oil up there will make the valve lash sound much louder. And as Musky has said, I adjust at half of what he suggests, Instead of .010 & .012, I do them at .009 & .011, because with a 357 cam, the base circle on the cam where you get your adjustment, is really small, and if you get them a bit tight (engine at full temperature) the valve adjustment can overlap to the point where engine runs really crummy, especially at higher race rpm's, and full throttle street RPM's. Just my 2 cents worth. Also since I started going one thousand larger gap on both, noticeably more clatter in valve train. Like some one else here said, rocker box is aluminum on both alloy head, and Iron head, so noise would transmit the same, I THUNK. I THUNK it is the 357 cam adjustments, that makes the difference in the clackety noise level, in the valve train ???? But I am no expert by any means, ask Musky ? Or what say you Musky ?? >> your thoughts ?
BILL
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G'day Bill. I'm no more expert than you Bill. I go by trial and *problem* and test by seat of my pants.
As far as tappet clearance goes 8 & 10 worked fine while running methanol but on petrol and pushed hard the gaps closed up enough to prop the valves open. 10 & 12 have so far been OK.
If an oil problem is suspected open the tank and put a finger over the hole in the return pipe. This will force a full flow of oil up there and may indicate a problem if it quietens it down a lot.
Alloy heads amplify any tap or click. Try putting some hard rubber between the fins (like the old 2 stroke bikes) I have used old conveyor belt cut into little squares.
Cheers
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Big snip
Alloy heads amplify any tap or click. Try putting some hard rubber between the fins (like the old 2 stroke bikes) I have used old conveyor belt cut into little squares.
Cheers
Old "smart" clutch cush drive rubbers work really really well and you can usually get then for free from any shop that does BSA's or perhaps an friend or club member.
For some reason no one ever seems to throw them out.