1979 35hp JOHNSON FIRES BUT WONT START

[FISHBONE74]

79 Johnson 35hp Any Suggestions Motor Turns Over Smokes Backfires But Will Not Start And Run I Have Changed Plugs Cleaned Carb Re-wired New Gas Tank And Fuel Line . Any Help Will Be Greatly Appriciated

Fishbone74

 

[wavrider]

Re: 1979 35hp JOHNSON FIRES BUT WONT START

Welcome to i-boats

sounds like it may be a timing issue, check your flywheel and see if the key is sheared.

you can also try spraying pre mixed fuel and oil into the throat of the carb to see if it starts then, possible not enough fuel getting to the cylinders.

 

[Lakester]

Re: 1979 35hp JOHNSON FIRES BUT WONT START

79 Johnson 35hp Any Suggestions Motor Turns Over Smokes Backfires But Will Not Start And Run I Have Changed Plugs Cleaned Carb Re-wired New Gas Tank And Fuel Line . Any Help Will Be Greatly Appriciated

Fishbone74

hello,

is it backfiring before or after u did all this rework and service?
when did it last run ggod?

too lean, weak ignition, improper timing, imporperly installed items, like plug wires, etc., failed internal seals, etc all can contribute to backfiring.

regards,

lakester

 

[HighTrim]

Re: 1979 35hp JOHNSON FIRES BUT WONT START

Backfiring out of the exhaust port is caused by having the ignition system fire a particular cylinder when the exhaust port is open ( ie piston down). This would sound like a shotgun going off..... is this the condition that you're experiencing?

This is usually due to a sheared flywheel key, a flywheel with melted (moved) center sensor magnets if they exist, timer base leads routed incorrectly to the powerpack, or having the leads from the powerpack to the coils reversed to mention a few.

Spitting back, sounding like a mild backfire, indicates a carb slow speed restricted jet..... something causing a lean carburetor scenario.