Tips for Checking Valve Clearance?

[Mark3Cam]

Iam currently using the kick start to index my way to TDC on the compression stroke to check my clearances but can’t quite find the sweet spot without the valve springs jumping ahead. I suspect this is leading me to being unable to slide even my smallest feeler gauge to get an accurate read. The motor is out of the bike. Any suggestions? Much appreciated!

[George]

Try putting in top gear and use spanner on nut holding rear chain sprocket. A pencil down spark plug hole is not really accurate enough. A piston positive stop and timing wheel will give a better result

[Mark3Cam]

Thanks George, I’ll give it a go. Unfortunately I have neither of the tools specified so will have to find a way to make do.

[ducwiz]

Iam currently using the kick start to index my way to TDC on the compression stroke to check my clearances but can’t quite find the sweet spot without the valve springs jumping ahead.

Are you shure to have the motor in the compression TDC? Sounds like the exhaust TDC, where both valve springs are under load.
And: take the spark plug off, otherwise you have to work against the gas pressure at the compression stroke.

cheers Hans

[Geordie]

The magnets in the alternator can resist the crank settling on TDC.

[ducwiz]

Well , that's right, often overlooked.

[Mark3Cam]

Yup spark plug out but you are right, can’t slide even my smallest feeler in there on exhaust and intake. I thought I was getting TDC for compression but clearly Iam just getting to know this engine…appreciate the insights.

[Mark3Cam]

Iam currently using the kick start to index my way to TDC on the compression stroke to check my clearances but can’t quite find the sweet spot without the valve springs jumping ahead.

Are you shure to have the motor in the compression TDC? Sounds like the exhaust TDC, where both valve springs are under load.
And: take the spark plug off, otherwise you have to work against the gas pressure at the compression stroke.

cheers Hans

Iam beginning to think it may be easier if I put the engine back in the bike and control the rotation with the chain and wheel but was hoping I can do this check without doing that

[blethermaskite]

Put the engine in first gear and use a ring spanner on the gearbox sprocket nut to rotate the engine to tdc on the compression stroke, then jam the spanner to prevent crankshaft rotation in either direction maintaining a tdc position for valve clearance checking/adjustment.(note-- this method is not accurate enough for ignition timing setting )
Cheers
George

[ducwiz]

For valve clearance adjustment it is not necessary to adjust the T.D.C. precisely, such as +-1° or so. See the illustration of the valve lifts in https://store.schnitzracing.com/cam-lob ... explained/. We see there is plenty of angle with no lift, along the base circle of each cam. You can put the angular position of the crankshaft almost anywhere inside this angle, then adjust the clearances.

Hans