Re: 25 HP
There are usualy two marks on the cam, one "top" and one "set" Rub blocks should rest at cam at the "set" mark when adjusting gap. After setting and putting flywheel back on, test spark by letting both sparks jump equal gap at around 1/4". If both do with a clear blue flame, spark isnt the issue. It sounds like you either need a good carb cleaning or richer low speed adjustment, by simply turning the low speed needle slightly out. When rereading your post, it seems like the miss only occurs when accelerating. Try pressing primer bulb when problem occurs. If that helps, chances are you have a weak fuel pump, or airleak in line or plug at tank/motor, hose connections. If that dont help, remove carb and take a close look at the small orifices just above butterfly. At midrange the motor gets major part of mixture thru the small openings on intake side of throttle butterfly. Clean them with a hair from a wire brush or so.