Depending on which engine you have, you may need to start it at a low idle and let it warm up slowly, about 1 minute.
Advance the throttle slooowly . If that does not work richen the low end needle about 1/4 turn,or if it is air bleed carb you may have to turn your needle in a little. A good way to adjust a air bleed carb is to open the needle then insert a pin partly in the air hole and then gently turn needle in untill it contacs the pin, remove the pin then start engine. Bob[:-]