Rodney,
Is this the one that has a toggle switch controller ... nothing, then wide open throttle?
If so the controller is the problem. It might need cleaning, might need adjusting, and if it's full of tiny little carbon disks it might need to have some replaced. If a controller with the carbon disks is dropped they can break. That will mess up the conductivity.
You can also get modern resistance controllers too. Generally they are less expensive than the electronic ones.
Joe