https://www.askmehelpdesk.com/attachment.php?attachmentid=33018&stc=1&d=1284173510
Model# 13aj609g766
I put 2 new belts on for the drive system as well as a new spring for the belt tensioner part#s: 732-0384,754-0468,754-0467. Now you have to push the accel pedal all the way forward with all you might for the tractor to have any speed. I do see an adjustment on the accel pedal but it fits so tight against the floor of the tractor that even after I remove all the nuts the pulley still holds it in place

Hi,
Best I can tell you is to check the variable speed pulley. Do this with the amchine in neutral. Push the pedal and watch the movement. I have seen them wipe out the bearings and have the moveaable sheave seize. Either way it is a matter of removing it and replacing bad parts or lubrication and freeing it.
Peace,
Clarke

I think crigby is on the right track. I have had more than a couple of the variable speed pulleys have small strands of old belt stuck up inside of them and not work properly. You'd never know it until you actually take it out of the mower and have it in your hand.