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1979 johnson 15hp stumbles till half throttle,first start.

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fisherman894

New member
1979 johnson(15r79e).first start cold-choke on starts 2 pulls.warms up take choke off,will idle fine all day.go to take off acts like it is running on one cylinder till half throttle-than clears out and runs fine.will acell no problem.compression=105,110.carb rebuilt(had old cork float-had let carb soak in cleaner over night-blew out with comp air).motor will start and run fine in a barrel-no miss.water pump and t stat replaced.have pulled spark plugs when this happens-top cylinder plug wet.bottom cylinder plug dry.have checked fuel pump(removed,insalled bolt and nut on pump,primed bulb-pump tight.link and synch done.top ignition coil replaced.mixture adjusted for best possible idle,and performance.have also done decarb with seafoam.only thing not checked is if i am losing spark(possible cdi black box????)pleas advise this is driving me nuts!!!!!!
 
Reeds are just behind the carburetor ( not inside the crankcase ) and since owner states it idles fine, they are likely OK.---------------------Use a timing light on it and put the motor thru its paces.--Observe the timing light to see if there are spark issues.
 
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Sorry, it was late-my bad. The thought I was trying to convey was that if any reeds were broken, they would likely be inside the crankcase.
 
thank you for your replies.usually with electrical components(cdi box,coils etc)they work fine cold and crap out hot.but i will check spark on that cylinder next time out.
 
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