Here is a handy item; a throttle torsion spring for 95% of all Shoprider mobility scooters. Very often a loose or "sprung" pot spring will seriously effect your scooter's behavior. If your scooter creeps forward or backward with no push of the lever, then a worn-out spring is very often the culprit.
Unfortunately we do not have any installation instructions for the throttle pot spring. You would need to contact Shoprider directly to see if they have any installation information for your scooter.