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Old 07-18-2015, 10:47 AM   #29
Blue Thunder
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Quote:
Originally Posted by 8gv View Post
I see the valve and agree it us a problem.

Can someone help me understand how that valve caused the symptoms?
Sure. Without getting too overly technical a 4 stroke engine does just that. Intake, compression, power, exhaust. When the piston was coming up for the compression stroke, it wasn't really compressing much, hence the 45 psi of compression referenced earlier in this thread. The spark plug fires within a few degrees of top dead center. When that fuel/air mixture ignited it would blast right by that huge crack in the intake valve and backfire out through the throttle body. I'm assuming the valve pictured is the intake. If it's the exhaust valve the same thing would happen but the backfire would go out the exhaust port...
BT
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