Re: Symptom of reed valve failure?
A broken/ leaking reed in a multiple cylinder engine will cause that cylinder[with the bad reed] to act lazy.....depending on the size of the leak, the engine could run fine at WOT, but will always be lazy at idle/part throttle....a broken reed allows the intake charge being compressed in the crankcase to bleed away....so that particular cylinder will act lean...an extra shot of fuel down the bad cylinder will generally make it fire briefly.....an experienced tech can usually pick up a bad reed just by listening at the carbs when the motors idling...they make a distinctive sound...an engine with a bad reed will have the same compression in the cylinder as a good one would, unless the broken off piece caught in the piston/rings and damaged them....