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Colin WhiteTricks of the Trade 


by Colin White

Tickey Tappets?

ADJUSTING the valve clearances on your motorcycle engine is often a frustrating experience. Access to inlets in particular is very difficult; the carbs are in the way etc.

More often than not when you have completed the task they sound noisy and is seems a total waste of time.

Once again there is an easier way!

Valve train wear usually is the culprit, and if you look the valve stem, wear forms a hollow, which is often more than the clearance specified.
Hollow valve stem wear.

Try adjusting them without a feeler gauge. How is it done? - Let me explain.

Remove a tappet adjuster nut and measure its thickness with a calliper. Count the number of threads in the nut and divide it into the thickness measurement. You now have the pitch of the thread. For example a 6mm thick nut with 12 threads would have a pitch of 0.5mm.

Honda cam box - doing it the hard way.If the inlet clearance specified was 0.25mm, one half a turn would be an accurate clearance unlike the one done with a feeler gauge. Just remember to lightly seat the adjuster screw and back if off the calculated part of a turn.

On all the early Honda single cam fours I do the inlets 1/2 of a turn and the exhausts 1/3 of a turn.

It was worked out about 30 years ago.