Question on valve clearances on AV's site?

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.

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.

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:

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?

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

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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