Out of spec ex. valve clearance


7 replies to this topic
  • umu24013

Posted April 10, 2009 - 04:00 PM

#1

Just rebuilt the top end on my yz426. have checked valve clearance.
The intake is in specs while the exhaust is 0.25~0.30 (one valve) and the other valve's clearance is exactly 0.30.

According to the manual it must be within 0.20 ~ 0.25 mm

It will take a week or two for the shims I’ve ordered to arrive.

Can I ride my bike a little with such clearance until I get the shims (I don't want to damage the engine)?

BTW, I'm not racing it, just riding around one hour a day usually.

  • grayracer513

Posted April 10, 2009 - 05:35 PM

#2

What year is the bike? 2000 models had stainless valves, which are spec'd at .25-.30mm

  • 642MX

Posted April 10, 2009 - 05:38 PM

#3

Just rebuilt the top end on my yz426. have checked valve clearance.
The intake is in specs while the exhaust is 0.25~0.30 (one valve) and the other valve's clearance is exactly 0.30.

According to the manual it must be within 0.20 ~ 0.25 mm

It will take a week or two for the shims I’ve ordered to arrive.

Can I ride my bike a little with such clearance until I get the shims (I don't want to damage the engine)?

BTW, I'm not racing it, just riding around one hour a day usually.



I saw a guy race a Suzuki once with the valves too loose. It bounced a shim, exploded the bucket and ruined the cam. Wasn't pretty...

Not saying this is going to happen to you.... but if it was mine, I'd wait for the correct shim to arrive.

  • umu24013

Posted April 10, 2009 - 06:13 PM

#4

What year is the bike? 2000 models had stainless valves, which are spec'd at .25-.30mm


2001, Ti valves

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  • grayracer513

Posted April 10, 2009 - 06:20 PM

#5

The 2000 came with SS valves. Did someone install Ti? If so, they should be set at .20-.25mm.

  • umu24013

Posted April 10, 2009 - 07:01 PM

#6

The 2000 came with SS valves. Did someone install Ti? If so, they should be set at .20-.25mm.


I bought the head separately, 5JG00.
It has Ti valves I'm absolutely sure, I checked it.

My original question was that:

"Can I use the bike with increased exhaust valves' clearance as I don't have the proper shims at the moment? The shims will arrive one or two weeks later"

According to the manual the clearance should be 0.20~0.25mm

What I have, is 0.27mm for the right ex valve and 0.30mm for the left ex valve.

Thanks alot

  • grayracer513

Posted April 10, 2009 - 07:26 PM

#7

I do recall the original question. You don't mind my clarifying a couple of things prior to answering, do you?

You should shim to the correct specs, of course, but the loosest valve is out by only .002". You can probably run the engine without worry temporarily.

  • umu24013

Posted April 10, 2009 - 07:42 PM

#8

I do recall the original question. You don't mind my clarifying a couple of things prior to answering, do you?

You should shim to the correct specs, of course, but the loosest valve is out by only .002". You can probably run the engine without worry temporarily.


Thank you!
I'll reshim the valves to the proper specs as soon as the shim set arrives. And I'm not going to rev the engine up too high while the clearance is out of specs.





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