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General Minitrail Talk
Honda CT70/Z50 Registry
1970 CT70H Manuf. date 6/70 ser# 118130 other shop could not fix
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<blockquote data-quote="69ST" data-source="post: 165613" data-attributes="member: 5"><p>A valve can be severely tuliped and still seal well, though probably not for long. You'll have a problem if the seat, valve face, or both need to be resurfaced...or the the amount of valve recession is so extreme that there's no valve lash possible. At that point, no choice but a new valve + three-angle valve job. FYI, it's almost always the intake valve that wears...rarely the exhaust, or either valve seat. With 150psi cranking compression, the motor should run well until the lash goes away...creating an unwanted thermal compression release...if everything else is functioning as it should.</p><p></p><p></p><p></p><p>Great insight! I'm siting here wondering "wtf didn't I think of that, before now?" Not sure if that's true but it sure seems logical and with the beautifully direct simplicity of a correct conclusion. With a removable advance mech. reversed, you should get the occasional light pop and nothing more...once enough fuel has been ingested. The ignition fires every crankshaft rotation...once on the compression stroke and the "waste" spark on the exhaust stroke.</p></blockquote><p></p>
[QUOTE="69ST, post: 165613, member: 5"] A valve can be severely tuliped and still seal well, though probably not for long. You'll have a problem if the seat, valve face, or both need to be resurfaced...or the the amount of valve recession is so extreme that there's no valve lash possible. At that point, no choice but a new valve + three-angle valve job. FYI, it's almost always the intake valve that wears...rarely the exhaust, or either valve seat. With 150psi cranking compression, the motor should run well until the lash goes away...creating an unwanted thermal compression release...if everything else is functioning as it should. Great insight! I'm siting here wondering "wtf didn't I think of that, before now?" Not sure if that's true but it sure seems logical and with the beautifully direct simplicity of a correct conclusion. With a removable advance mech. reversed, you should get the occasional light pop and nothing more...once enough fuel has been ingested. The ignition fires every crankshaft rotation...once on the compression stroke and the "waste" spark on the exhaust stroke. [/QUOTE]
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General Minitrail Talk
Honda CT70/Z50 Registry
1970 CT70H Manuf. date 6/70 ser# 118130 other shop could not fix
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