I know that this forum is supposed to be answered by CEN only, but I know the answer. You need to lean the fuel mixture. You do this by turning the screw on the side of the carb clockwise. Factory settings have this screw set to flush with the surface, but this is really rich pruposely for break in procedures. Turn this only 1/8th of a turn at a time. The manual gives more detailed info. Look for low speed settings under the break in section.