Re: Motorized Bicycle Take a Tip...Leave a Tip
If you look, I'll bet your exhaust tip is greasy too. Exhaust blow out of unburnt 2 cycle oil. Happens to me until the cat converter gets warmed up, it can take 10 minutes or more of riding to heat up enough to burn all the fuel/oil unburnt by the motor.
If it's a relatively fresh motor & you're still breaking it in with double oil as recommended, this is normal, just carry a rag with you. If not, then you may be running too rich an oil mix or the carb itself is jetted too rich (try dropping the carb needle a notch, see if it helps).
By the holy power of Love, Life & Laughter, I commend you to Go Forth & Be Awesome!