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Johnson 35 hp miss fire

H

ht43

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I have a 79 johnson 35 hp it has a strong miss fire about every 10-15 seconds when it is idling and the bottom spark plug is fouled and had moisture on it when I changed it, does anyone have any ideas?
Thanks, Rob
 
I would suggest checking the ignition circuit. Do you have spark testers.? They go between the sparkplug and the plug boot or high tension lead. You can usually buy them at auto stores or marine shops. Or even some Harley Davidson dealers have them for looks. They come I red or blue. You want to see if the spark is dis appearing at idle. If it is I would suggest changing the power pack.

Another suggestion could be the carbs air jet. Sometimes over time the carb can be sucking air from loose butterfly shafts. Which will cause too much air in the mixture. At the top of the carb should be the air jet. Correct me if I am wrong about the location

. But if you get a small twist tie and double it up and put it in the air jet. Without losing it in there. Tie it off somehow . And see if that stops the misfire.
 
Is the problem actually a misfire or is it the common problem that engine have... hesitating, spitting back thru the carburetor, that sort of thing that is present at an idle?

If possibly the latter, while this problem is present, stick two fingers into the carburetor throat, acting as a manual choke to enrichen the fuel flow. If the problem vanishes, either the slow speed needle valve needs to be backed off slightly or the SS jet needs to be changes, whichever your carburetor has.

Also, if the engine has been sitting for quite some time, it's very possible that the carburetor simply needs cleaning and rebuilding due to fouling.

Let us know what you find.
 
That motor has a conventional slow speed mixture knob. Simple things first---just give the knob a tweak to the left and see if that clears it up. Lean sneezing is caused by, well, running too lean.

It also has an intake silencer, making it difficult to do things like sticking your fingers into it.
 
fdrgator said:
That motor has a conventional slow speed mixture knob. Simple things first---just give the knob a tweak to the left and see if that clears it up. Lean sneezing is caused by, well, running too lean.

It also has an intake silencer, making it difficult to do things like sticking your fingers into it.
Click to expand...

It requires a strong mind, stiff arm to fingertips, and swift non hesitant action, while making a loud blood curdling yell such as EEEEEEYYAAAAAHHHHHH!! :p (Ordering new silencer mandatory).
 
The silencer is actually gone so I will try that, and some of the other suggestions. Thanks. I'm not 100% sire if it is missing or hesitating, but it's idling fine for mabe 10 second in between misses and when it does it the engine nearly dies It does it so severly.
 
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