Valve cleareance

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Hi Guys,

I did valve adjustment on my friends CBX and some of the valves ended being slightly over.13mm at .14/.15mm.
Is this acceptable at all?

Thank you
Sasha

[daves79x]

It's fine. Rather be a bit loose than too tight. However, those that are .006 inch could be taken down to .004 very easily. Assume it was lack of proper shim sizes?

Dave

[steve murdoch icoa #5322]

I couldn't find the thread i was looking for about a top end racket but i did find this article with some info on valve clearances.
http://www.motorcycleproject.com/text/v ... ances.html

Seem to remember too loose being a bit noisier and way too loose being hard on valve stems.

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Yes, it was the shims, I have nothing to make it any lower.

Thanks dave

[herdygerdy]

The head of a valve, in particular the far hotter exhaust valve, that has a wide clearance will spend much more time 'at rest' on the valve seat, compared to a valve that has minimal or next to no clearance.

This extra time spent 'at rest' on the valve seat allows more time for the latent heat in the head of the valve to be transferred into the head through the valve seat and for that heat to be carried away from the head by cooling air and oil. So the head of a valve with a large clearance will not build up heat and so will therefore run cooler than a valve with minimal clearance.

This is why folks who set their valve clearances at the minimum in the hope of a nice quiet motor, sometimes end up with valves leaking and burnt at under 1,000 miles.

And that is also why old school wrenches use the maxim 'A noisy tappet is a happy tappet'.

Cheers..Tony

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Great info, thank you

Sasha

[mlynch001]

Out of the crate, HONDA set the valve clearances at the high side. This is because the valves and seats tend to "Break in" and close up on a new bike. The first adjustment on any HONDA with the CBX Style valve train is usually the one that requires the most time and the most radical shim changes. These valve trains are almost "Set it and Forget it"! I had a 1980 CB750F that had exactly one valve adjustment shim change in 30K Miles. These HONDA valves and seats are very hard and once they seat in, the just do not change, unless you run a lot of dirt through the engine. Setting the valves toward the tight side of the spec is fine on a fully broken in engine. I always set the exhausts toward the loose side of the spec and the Intakes closer to to the middle, when possible. Also note that HONDA used some very selective fit shims in their "NEW" engines. There were actually "half step" and "quarter step" size shims that did not show up in the parts book. When I worked for HONDA, we kept EVERY shim we took out of a "First adjustment" bike, since those shims were often these intermediate thickness shims which were otherwise not available.

[Larry Zimmer]

Thanks for the 'tidbit', Lynch. Wondered where those 1/2 size shims came from.

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Thank you for the valuable info.
I always try to get my shims as close to .13mm as possible only here my question was if it's ok to have few valves at .14/.15mm which is slightly over max gap of .13mm