HELP 1975 Johnson 9.9 won't idle good

[bowfisher2636]

Alright guys I have a 1975 Johnson 9.9 I'm running it and it will not for the life of me idle for long but when I move the throttle on the carb it will scream and run like a sewing machine but when I bring it back down to a idle it will try to die out any ideas on what's going on?

 

[flyingscott]

Have you checked for spark? or done a compression check?

 

[bowfisher2636]

Spark and compression are great and the motor is running it will just only run good at more than half throttle I just took the carb Apart and it's clean Also no crud build up

 

[hardwater fisherman]

Are you just giving it gas by hand at the carb?

 

[bowfisher2636]

Yes I was on the handle and it almost wasn't enough so I started at the carb with the throttle as far as it could go because of the timing advance the throttle will only go so far in neutral due to that stop plate

 

[flyingscott]

Did you do a cylinder drop test? Have you gone through the points and condensers? Have you thoroughly cleaned the carb and put new parts in.

 

[bowfisher2636]

Carb was rebuilt and I recently set the points to .020 the motor has sat for a few months so I went and did the points and the carb rebuild I need to do I cylinder drop test. While it's running the motor every once in awhile will make a noise like it hits and then kinda flutters idk if im explaining it right but it's like it's running then this hit noise then kinda flutters and the motor is running fine again almost like a car lopping with a cam in it

 

[flyingscott]

Check the magneto plate make sure it's tight and not a lot of slop. Your sound could be a lean sneeze which would be a carb problem. Another problem with them is the ignition system the points and condensers need to be in good shape. If you replace the points and condensers use only factory parts. Are you running champion plugs

 

[Pusher]

My dad never had much luck with his Johnson. We just make it a point to avoid them now.

I had a similar issue on my motorcycle. Ran rough at idle, then took off like a bat outta hell. It ended up being that the spark advance which was a centrifugal force system was broken so the arms wouldn't open outward until I could gain RPM. It's probably nothing to do with your 9.9 kicker but might spark something.

What if your spark plug leads were corroded on the ends? That would give you a weak spark at idle then strong at higher RPM right?

Might be some cloth lint got caught in your carb after the clean up. I've heard of that happeneding on an aircraft carb rebuild.

 

[F_R]

Opening the carb with out advancing the spark is only confusing the issue. In the real world they must operate together and be properly synchronized. OK, having said that, a lean sneeze at idle can be a carburetor problem, or a synchroniztion problem or a crankcase sealing problem.

Not meaning to throw discouragement into the discussion, but that model was a p-poor running motor. Fouled plugs happened almost daily (or sooner) on some of them.

 

[bowfisher2636]

alright guys update its still sneezing a little bit but i went back through and combed the carb once more i must have missed something the first time it is running alot better at idle with the occasional sneeze here and there other than that i believe i have fixed it

 

[Pusher]

Glad it's running better. It might improve once the varnished gas has loosened up

 

[oldboat1]

Think I would try to continue progress by tweaking the idle mix a bit -- should be able to dial out any lean sneezing if all else is working well. Carb cleaning for an idle issue means opening up the passages at the top of the carb, and cleaning them out. (I prefer soaking the carb top after removing the domed plug, then spraying passages -- should be squeaky clean, no varnish.) But sounds like you are close. Turn the needle counter clockwise about 1/8 turn at a time to try and get rid of the lean sneeze. If the motor lopes or stumbles, the setting is too rich (clockwise needle correction). If the throttle idle stop knob on the side of the motor is working, you can set it at the lowest smooth idle obtained with the mix adjustment -- keeps you from killing the engine by throttling down too low.

 

[Sirrobin53]

Link and sync? Absolutely a must.