Neville the problem could be numerous things but lets try the simple ones first. a bad throttle pot or speed control pot can cause that problem. Both of those are located in the tiller console and that has to be removed to test them. You can ohms check both with power off and you can voltage check them with power on. You should get a smoth change in resistance as you turn th speed pot and as you move the throttle forward and reverse with power off. alsdo chech the connections in the tiller and remove the seat and battery cover and check the connections at the rear of the scooter sometimes just moving the wires can get it moving again but that won't help you locate the problem if you can't isolate the bad connection or bad wire. Scooters are tough to repair because of the many connectors that they have and the cables runnig front to rear that can cause problems especially with Pride scooters Good Luck I know I didn't give you much but I'm not fond of working on scooters Hope this Helps