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Question on valve clearances on AV's site?

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I was browsing through AV's website yesterday(great site btw). When I got to the valve clearance section, one thing didn't make sense to me, maybe someone can clarify.

When he did his first valve check on 7/8/06 he recorded these measurements:

The valid range for the exhaust clearance is 0.17 to 0.22mm

Left exhaust valve (pad/clearance), #182/0.152mm - out of spec.

Right exhaust valve, #180/0.229mm - in spec.

He says that the right exhaust valve is in spec. But isn't 0.229 greater than 0.22.

Anybody?

Thanks.

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It's not really in spec, but clearances will typically tighten, or get smaller as the valves wear. The right ex. valve has room to tighten a bit with wear, but the left ex. valve has already worn past the low limit.

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It's not really in spec, but clearances will typically tighten, or get smaller as the valves wear. The right ex. valve has room to tighten a bit with wear, but the left ex. valve has already worn past the low limit.

Spot on. I usually run my valves a little on the looser side of the spec. My sons 2008 YZ250F has almost 100 hrs on it and the last time I checked they were all within spec but the exhaust valves were about .18 (.17 being the limit) so I put the next smaller shims in. This is the first adjustment I have had to do on the valves and it was only the exhaust valves. Running the .009mm larger than spec shim is just fine. :busted:

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Spot on. I usually run my valves a little on the looser side of the spec. My sons 2008 YZ250F has almost 100 hrs on it and the last time I checked they were all within spec but the exhaust valves were about .18 (.17 being the limit) so I put the next smaller shims in. This is the first adjustment I have had to do on the valves and it was only the exhaust valves. Running the .009mm larger than spec shim is just fine. :busted:

Thanks for the reply guys, that makes sense.

So when valves wear they always get tighter, not looser right?

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Not on all engines. Valvetrains that use rockers will loosen over time,unless they are using hydraulic lifters

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Tim - that right exhaust valve was very slightly out of spec on the loose side, but we're talking 0.009 of a millimeter so that's pretty small. Anyhow, since it was on the loose side, I didn't worry about it since it will wear down and tighten up eventually. :busted: If you're out of spec on the tighter side, then you really should reshim.

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