you can also try leaning out your low speed needle (the one on the side of the card by the throttle arm of you have a rotary carb if you have a slide carb then refer to your owners manual that came with the motor to see where it is located because some slide carbs have two or three needles). Only turn it in 1 hour increments untill your engine accellerates without any lag. You have to be carefull not to lean out the low end too much or youll cook the motor. Leaning out the low end too much can do just as much damage as leaning out the hi end too much.