1981 Johnson 50 running rich - HELP!!

acmjg

Recruit
Joined
Jun 14, 2009
Messages
5
I have a 50hp Johnson that I just rebuilt the carbs on and it now runs real rich on the top end. I have pulled all the jets, they are all clear, the floats are set properly and seal well. Compresson is 125/130, reeds look good.

These carbs are all fixed jets so no adjustments.

The engine idles great. On a slow throttle up, I get a slight lean condition, but one past that point it runs well up to 3/4 throttle. At full throttle, it goes really rich. I have run the engine with the flame arrestor off the front so I can see into the carbs as this is happening. as soon as the main jet starts feeding fuel, it goes real rich- to the point of spitting out the front of the carbs. If I pinch the fuel line to either carb, the rpm comes up as the carb runs dry. Both carbs have the same condition.

I have worked on engines all my life, but this one is stumping me. Such a simple carb, I must be overlooking something.

Thanks,
Anthony
 
Last edited:

Fl_Richard

Lieutenant
Joined
Jan 21, 2005
Messages
1,428
Re: 1981 Johnson 50 running rich - HELP!!

Spitting usually indicates reed valves arnt closing properly. Do all carbs spit?

I'm assuming the problem wasnt there before you re-built the carbs.
If not...
Could be...
a float problem. Are you sure you re-built the carbs properly?..
Plugged hi speed nozzle vent.. Are you sure you re-built the carbs properly?..

Why did you re-build the carbs? Was there an earlier problem?
 

acmjg

Recruit
Joined
Jun 14, 2009
Messages
5
Re: 1981 Johnson 50 running rich - HELP!!

These carbs have been cleaned before because they were varnished up from not being used. They worked fine after the last cleaning. I cleaned them again this time just because the boat was sitting again and cleaned them as a precaution because I expected them to be dirty again.

After this cleaning, they started the rich run. It is both carbs. I just checked the fuel pump and the diaphgram is good. (I have had bad diaphgrams before which pumped gas directly into the crankcase). Not the case this time. Tell me more about the hi speed nozzle vents?? Floats are set properly and needles seal well.
Anthony
 
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