no guessing!

[nert]

when adjusting valves on a standard OHV engine with pushrods and rockers, valve clearance becomes less as the engine gets hot. Mostly due to the expansion of the push rod growing longer.
In an overhead cam engine, like our GS 2 vlave engine, would the clearance grow greater with a hot engine? The aluminum head would expand taller, raising the cam journals higher away from the valve shim bucket, and the valve head lower at a greater rate than the steel valve stem would grow. Any one know for sure?
thanks

[first timer]

you do valve adjusting with the engine stone cold, that means you can not start the bike for at least 24 and it should be kept out of the sun as well.

-ryan

[nert]

yes, i know that. I am wondering what actually happens to the clearance as the engine gets hot. Greater (atypical) or less (typical)? So often, one shim size either way puts the clearance very close to the low limit or close to the highlimit. Wondering which way is better. If clearance increases with hot engine (atypical) than the tighter adjustment would be better.

[Detman101]

I've often wondered the same thing....
I'm glad you had the mental acuity to put it to words.


Dm of mD

[KEITH KRAUSE]

If in doubt, always go with the wider clearance. Too tight or "borderline" can burn a valve. Too loose accelerates wear over time. Are you aware of "fat" shims? They will have an "X" after the stamped size.
Example: 2.55X A typical "fat" 2.55 shim will actually be 2.57 or 2.58
These make adjusting a lot easier.

[nert]

was not aware of "fat" shims. I have them. Didn't know what the "X" was for. Thanks. But?

[Anonymous]

fter you do your next valve clearancing check them again after you test drive the bike. That should answer your question.

[KEITH KRAUSE]

As for what happens to clearances after the motor is hot, they tighten up.
Some metals expand more than others and some faster than others. Some hold their heat longer and take longer to cool down. That's about all I know on the subject. With the fat shims, you should not have any trouble adjusting.