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1965 9.5 HP Johnson MQ-11C - Rough Idle Help

Persistent cough ( lean sneeze ) at idle is caused by wrong fuel mixture on low speed.-----Adjusting mixture may help.----Throttle plate MUST be closed at idle for low speed circuit to work.----If throttle opens too early the motor might sneeze and stall.-----There is an adjustment for throttle plate opening.----Have you set that correctly or no idea?
 
Correct....agreed. A bad crankshaft seal can lean the mixture on it's adjacent cylinder. Most commonly it's the upper cylinder on these. You can isolate or identify which cylinder if you know what your doing. Soapy water may not be the MO here.
 
Racer......thanks for the "lean sneeze" insight.....I've verified that the throttle plate in the carb is fully closed at idle.....while doing so, I've re-cleaned the carb with emphasis on the low-speed circuit.....I know for sure the synchronism is properly set...I'm going to try to tank test it again in a few days.

Tim...soapy water was the best thing in my toolbox....there were absolutely no (zero) signs of an upper seal leak. Any suggestions on how to test the lower seal?
 
Post #64 here.--And still solution ?----Those blinky spark testers no good in my opinion.-----Does spark jump a gap of 5/16" on both leads, yes , no or no idea why this is important information ?
 
Built my own spark jumper per Timguy's suggestion.....definitely jumps 1/4 inch on both leads....all new ignition system, copper spark plug leads....and I understand the importance.

Have read some stuff about weak magnets in flywheel....ever experienced that? If there's any merit to it, what is solution to strengthen the magnets, assuming this can be done?
 
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