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Discussion Starter · #1 ·
I just got done putting in a carb kit and uping my jet sizes fron a 122 to a 125 and 38. I set the pilot screw 2 1/2 -2 3/4 out and it would run good but on hard revs it would puff black smoke out do you think this is carb cleaner burning off ? I used a spark plug to tell if it was running rich or lean and think I have it set good but I am still wondering what up any help?
 

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If it's putting out black smoke, it's running rich. That won't have anything to do with the pilot screw. The pilot screw just adjusts the air/fuel mixture for the idle circuit.
 

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Discussion Starter · #3 ·
OK so i need to go back down a jet size in the main what about the slow? still not sure what the differance is between the two.
 

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The pilot jet, and pilot screw control fuel delivery from idle to approximately 1/8 throttle. The main jet primarily controls fuel flow between 3/4 and WOT (wide open throttle). The needle and needle jet are the components that regulate fuel flow between 1/8 and 3/4 throttle.

If it idles good and runs good up to about 1/8 throttle, I would just go down a size on the main jet and see what that does.
 
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