If the motor is good when cold, but maybe starts to gurgle when it warms up then it's possibly rich. Also, if it starts easily from cold, but is harder to start when warm then it's probably rich.

If it's tricky to start and requires choke for a while before it runs properly then it's probably lean.

If, when it's running it goes....Bwaaaaaaaaaaaaaah... when you whack open the throttle and nothing happens then it's probably lean.

Any chance of some engine and jetting specs? Might make the job of solving the problem easier.