Hitchcocks Forum

I cant seem to stop quite pronounced tappit noise have checked clearance installed new rockers and valve guides, checked oil feed by slacking off banjo bolts hope someone can help

Simple question first, what tappet clearance are you setting to?

REgards, Mark

Bullet engines are pretty noisy, even when set up correctly. The correct setting is nil clearance when cold.

Tis the rule of thumb, cold engine, engine at top dead centre on the compression stroke.

If you cannot move the push rods with a thumb the setting it too tight, if they move easily they are too slack.
If they move with a light thumb pressure that is just right.
(Not easy to get just right as tightening the lock nuts can alter the setting.)

Hi, check for sideplay and wear in the tappet blocks and if your on original carb a worn slide can give similar sound, with engine running press your finger against the slide to see if noise disappears, I have this problem on a BSA M20. Vince.

You could try a set of indian adjustable cam spindles made a big difference to my bike but dont know if they would fit a redditch bullet, theres a lot of slop in cam gears.

I used the eccentric cam spindles in the racing engines a few years back, but found they could twist round in their locating holes in the crankcase because they don't have a very large flat on them to register on the ledge in the crankcase and cam bushes can sometimes be a close enough fit to induce this problem, which can then put immense strain on the timing gears and the end of the timing side mainshaft. Our 350 racer had to pull out of a race it was doing well in at Cadwell a few years back, because a cam spindle had slewed round and prevented a valve from closing and the engine just slowed down and stopped, luckily with no damage, but that was enough for me to do away with them. The Redditch cam spindles have much larger flats on them to register in the crankcase. I would rather a bit of clatter and stick with the latter type. Regards, Paul.

"They all do that sir". Noted for it. Depending on how original your 1951 is, it should be well worn by now and most likely a bit loose and sloppy. By now it probably has a cumulation of out of tolerance parts all adding to the clatter. Whilst it is possible to restore it to factory blueprint, it probably adds to the charm of running an old bike. How much time, effort and money do you want to spend on it? Adjust as best as possible.

Sorry jefrs, I know I'm being pedantic but this drives me to distraction.
You can not adjust something as best as possible. You can adjust something as well as possible or the best you can, but qualifying a superlative is just bad grammar.
I know, I know, it's sad but I can't help it. I even hear it on Radio 4 these days, it's deplorable.

When the valve-stem end caps are well worn (dished) and there is excess end-float on the rocker shafts, then 'tappet' noise is frequently more noticeable...