Proper carb jetting


New Member
Jan 15, 2021
Yesterday my bike sputtered out like it was starving for air ( i thought)..i went home pulled off air intake and it still did it so i puked start plugs and it was black.. So i replaced it and it ran fine. But i understand black spark plugs are a sign of too rich


Active Member
Jan 12, 2017
Possibly too much oil if you're running a 2 stroke. Try adding a bit more gas to the mixture before putting it into the tank. If you aren't already, I suggest using a premix jug, or some measuring cups you will never use for cooking again. Ideally, if the engine is new, you'd want to use a minimum of 32:1 FOR (fuel/oil ratio). If not new, generally no higher than 42:1 is recommended except with some very special, and expensive, synthetic oils.

If that doesn't work, try moving the needle clip up one notch at a time until it runs better. If it still sputters, rejet with a smaller one, move the clip to the middle of the needle, and keep adjusting until your engine runs right. Be careful though, I ran too lean on one of my engines and blew out the spark plug core...literally. The base stayed in the engine. I think my photo is still hanging around here somewhere...

If you're using a 4 stroke engine, chances are that the black is soot, which definitely means rich mixture. Lean it out some with a high flow filter, or a smaller jet.