Re: pull start works great!! However......
H28, You need to get specific on the model and serial so we can really identify your motor.
Check the obvious things. When did this problem start? Is the stop lanyard clipped in? Is the fuel line primed? Is the choke working? If it's an RC setup, are you pushing in on the key to operate the electric choke? If it's a model with ABS solenoid (instead of choke), does the motor run OK after it is warmed up?