is it common to have valve guides go out? 945rr - Honda Motorcycles - FireBlades.org
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post #1 of 2 Old 06-16-2014, 10:12 PM Thread Starter
 
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is it common to have valve guides go out? 945rr

I have a cbr954.. cracked a valve.. my machine shop told me all my exhaust guides are bad. turns out they are backordered from honda and can take 2 months to get. I bought some used heads and he is telling me that two of these exhaust guides are bad on this one also. I am now thinking he doesn't know the tolerance to check. since they are exhaust guides, shouldn't they be a little more loose from the factory then the intake guides(or valve stems) or are they the same? I imagine that they need room for expanding since the exhaust valves are not cooled by incoming fuel. I need my bike back and cant afford to wait or to keep buying heads until he find ones he likes. I would think there should be some wiggle in the guides/stems until the motor heats up to normal temp. Does titanium expand more or less then steel or alum? I have a race motor for a chevy and my forged pistons dont set to spec until the motor is warm. Opinions? Thanks in advance.
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post #2 of 2 Old 06-17-2014, 12:36 AM
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Re: is it common to have valve guides go out? 945rr

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Originally Posted by venicegrey View Post
I have a cbr954.. cracked a valve.. my machine shop told me all my exhaust guides are bad. turns out they are backordered from honda and can take 2 months to get. I bought some used heads and he is telling me that two of these exhaust guides are bad on this one also. I am now thinking he doesn't know the tolerance to check. since they are exhaust guides, shouldn't they be a little more loose from the factory then the intake guides(or valve stems) or are they the same? I imagine that they need room for expanding since the exhaust valves are not cooled by incoming fuel. I need my bike back and cant afford to wait or to keep buying heads until he find ones he likes. I would think there should be some wiggle in the guides/stems until the motor heats up to normal temp. Does titanium expand more or less then steel or alum? I have a race motor for a chevy and my forged pistons dont set to spec until the motor is warm. Opinions? Thanks in advance.

Sounds strange to me.
Unless the engine has been _very_ poorly maintained I can't see the guides being worn.
Check them yourself, specs are in the manual.
Yes, exhaust valve guide clearances are larger than the intake clearances - 0.010mm to 0.037mm and 0.020mm to 0.047mm
I doubt you'd notice any significant "wobble" unless they're very worn.
They're not titanium. Aluminium expands more than steel and ti, ti expands slightly less than steel - depending on the specific alloys.

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