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J50BELCN, 7/2013
manifestation
after running fine on 2 outings, the day started out running fine. 15 minutes later, after I hit the throttle entering Pleasant bay from little Pleasant bay I hit a couple of bumpy waves. The engine started running at less than 1/2 speed, running rough. Same at idle: very rough, stalling, the idle lever made little difference in engine speed.
evidence that I should have given credence to
lower carburetor had a little gas dripping out the air intake.
tests
fuel bulb seemed to pump up fine. But it slowly got un-firm. Pumping it while underway made no difference
removing either plug wire caused stall
plugs looked OK. similar to each other
compression was good, same on both cylinders
stator coil and charge coil resistance within specs.
spraying starter fluid in upper carb caused engine to speed up, spraying into bottom carb had no effect.
holding plug wires close to block, spark had no trouble jumping 1/2"
solution
Lower float was banging into the roof of the bowl before that little pin had shut off fuel flow into the carb. Excess fuel dripping out the front of the carb and was making it run rough. Hitting those bumps must have bent the float.
the wild goose chase (or troubleshooting by credit card)
There was a crack in one of the coils, I replaced it. The voltmeter wasn't reading the right peak voltage output from the power pack (though you can't measure that with a voltmeter). Replaced it. thought maybe the fuel hose was collapsing inside. Replaced it. Swapped out the fuel pump with one I had, after pulling it from the head and finding no evidence of fuel leaking from vacuum hole. Replaced fuel lines in motor (They looked pretty crappy anyway). Anybody need parts?
manifestation
after running fine on 2 outings, the day started out running fine. 15 minutes later, after I hit the throttle entering Pleasant bay from little Pleasant bay I hit a couple of bumpy waves. The engine started running at less than 1/2 speed, running rough. Same at idle: very rough, stalling, the idle lever made little difference in engine speed.
evidence that I should have given credence to
lower carburetor had a little gas dripping out the air intake.
tests
fuel bulb seemed to pump up fine. But it slowly got un-firm. Pumping it while underway made no difference
removing either plug wire caused stall
plugs looked OK. similar to each other
compression was good, same on both cylinders
stator coil and charge coil resistance within specs.
spraying starter fluid in upper carb caused engine to speed up, spraying into bottom carb had no effect.
holding plug wires close to block, spark had no trouble jumping 1/2"
solution
Lower float was banging into the roof of the bowl before that little pin had shut off fuel flow into the carb. Excess fuel dripping out the front of the carb and was making it run rough. Hitting those bumps must have bent the float.
the wild goose chase (or troubleshooting by credit card)
There was a crack in one of the coils, I replaced it. The voltmeter wasn't reading the right peak voltage output from the power pack (though you can't measure that with a voltmeter). Replaced it. thought maybe the fuel hose was collapsing inside. Replaced it. Swapped out the fuel pump with one I had, after pulling it from the head and finding no evidence of fuel leaking from vacuum hole. Replaced fuel lines in motor (They looked pretty crappy anyway). Anybody need parts?