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FJR Motorcycle Forums
Technical & Mechanical Problems
Valve check... Should I leave well enough alone or dig in
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<blockquote data-quote="Fred W" data-source="post: 1388071" data-attributes="member: 3828"><p>The valves wear pretty slowly on these bikes. The seats are hard and the valve faces seem to stand up to the hammering pretty well.</p><p></p><p>1st check data indicates that either the factory tends to set the intakes on the low end of their clearance range, or that those valves settle in considerably in the first 26 k mile interval. Since nobody in their right mind would check the clearances of a new engine (which has some folks pondering why I didnt do that) we may never know which it is. But, considering that the exhaust valves do not seem to be tight at first check, that would suggest that the former theory, that the intakes are set tight from the factory, may be more likely.</p><p></p><p>Those of us who, when an adjustment was necessary, have sanded the shims to the 70th percentile of spec have found that you will likely never have to adjust the valves again for the life of the engine. Why they only offer shims in .05mm increments is a mystery. If they were available in .01 mm increments people could swap shims to achieve the optimal clearance once and be done with it. Since the wear is so predictable in nature and direction, it also makes one wonder why the factory didnt set them all at the loose end of spec to begin with. Whatever performance difference there is in having the valve open more / longer is insignificant. Another mystery.</p><p></p><p>Cynics might suggest they are drumming up service business for their dealer network, but that doesnt make much sense for several reasons. Dealers dont seem to cherish valve work, and any avoided warranty or extended warrant claims would be money in Yamahas corporate pockets at zero increase in manufacturing cost. Plus, just think of the marketing value of saying no valve checks for 50k miles.</p></blockquote><p></p>
[QUOTE="Fred W, post: 1388071, member: 3828"] The valves wear pretty slowly on these bikes. The seats are hard and the valve faces seem to stand up to the hammering pretty well. 1st check data indicates that either the factory tends to set the intakes on the low end of their clearance range, or that those valves settle in considerably in the first 26 k mile interval. Since nobody in their right mind would check the clearances of a new engine (which has some folks pondering why I didnt do that) we may never know which it is. But, considering that the exhaust valves do not seem to be tight at first check, that would suggest that the former theory, that the intakes are set tight from the factory, may be more likely. Those of us who, when an adjustment was necessary, have sanded the shims to the 70th percentile of spec have found that you will likely never have to adjust the valves again for the life of the engine. Why they only offer shims in .05mm increments is a mystery. If they were available in .01 mm increments people could swap shims to achieve the optimal clearance once and be done with it. Since the wear is so predictable in nature and direction, it also makes one wonder why the factory didnt set them all at the loose end of spec to begin with. Whatever performance difference there is in having the valve open more / longer is insignificant. Another mystery. Cynics might suggest they are drumming up service business for their dealer network, but that doesnt make much sense for several reasons. Dealers dont seem to cherish valve work, and any avoided warranty or extended warrant claims would be money in Yamahas corporate pockets at zero increase in manufacturing cost. Plus, just think of the marketing value of saying no valve checks for 50k miles. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Valve check... Should I leave well enough alone or dig in
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