If you have done work on the carby maybe the throttle cable has popped out of the cam or the diaphragm is not seated properly and then again if it has a white poppet valve it could could be set in the wrong position.
We need a bit more information as to what you have done to the motor so that we can give the correct advice.
Regards,
Bruce
Please do not PM me asking for support. Post on the forums as it helps all members not just the individual.