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Everything Dirt Bike
Make / Model Specific
Yamaha
Does it make big difference if specs is barely off???
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<blockquote data-quote="SRAD97750" data-source="post: 204425" data-attributes="member: 425"><p>Alo,</p><p>You're going to want to shim it to the highest spec and check regularily to build up a good amount of data.</p><p></p><p>Metals expand as they heat up.</p><p>At operating temperature the clearances are tighter than when cold. This clearance you measure when cold may be all but completely taken up by normal thermal expansion at operating temps.</p><p></p><p>Why the clearance changes over time:</p><p>A valve stretches either at the stem or the face as it gets pounded vigorously in and out of it's seat. The more vigorous you are on the throttle, the more pounding the valve receives. This stretch is different than the thermal expansion, but rather a physical deformation due to use.</p><p></p><p>Like it or not valves are wear items that should be expected to move over time and once the 'acceleration of wear' increases, the valves/seats are on their way out.</p><p>Just my nickle fifty... -BIG DAN <img src="https://www.dirtbikeaddicts.com/static/images/smilies/thumb.gif" class="smilie" loading="lazy" alt=":thumb:" title="Thumb :thumb:" data-shortname=":thumb:" /></p></blockquote><p></p>
[QUOTE="SRAD97750, post: 204425, member: 425"] Alo, You're going to want to shim it to the highest spec and check regularily to build up a good amount of data. Metals expand as they heat up. At operating temperature the clearances are tighter than when cold. This clearance you measure when cold may be all but completely taken up by normal thermal expansion at operating temps. Why the clearance changes over time: A valve stretches either at the stem or the face as it gets pounded vigorously in and out of it's seat. The more vigorous you are on the throttle, the more pounding the valve receives. This stretch is different than the thermal expansion, but rather a physical deformation due to use. Like it or not valves are wear items that should be expected to move over time and once the 'acceleration of wear' increases, the valves/seats are on their way out. Just my nickle fifty... -BIG DAN :thumb: [/QUOTE]
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Everything Dirt Bike
Make / Model Specific
Yamaha
Does it make big difference if specs is barely off???
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