Have a 2004 Troy Built Bronco model J609 lawn tractor that loses all momentum going up an incline - engine is running fine at full throttle and foot pedal is pressed to the floor. Pulleys are spinning freely for transmission and on engine. The are 2 drive belts on this and the owners manual describes replacing them. Engine pulley is supposed to be lowered but the pulley spins freely. First off does this sound like the drive belts are the source of the problem ? If it is should the engine cover be removed and a wrench placed on the large bolt in the middle of the engine to hold the shaft in place or is there another way to lock the shaft so you can back the bolt out of the bottom of the shaft to lower and expose the upper engine pulley for replacement of the drive belt ? Is that bolt at the bottom a left or right hand thread ?

Mike C., October 2009

I am answering my own questions in the hope that others can learn from my experience. Troy Built did answer but their answers really directed you to a repair center. Here step by step is what was done to repair my lawn tractor
1. Begin by removing the battery and battery box
2. Remove the cutting deck
3. Remove the rear wheel on the right side
4. Unbolt the bracket behind the left rear wheel that holds the double pulley assembly in place
5. There is a small bolt in front of the frame mounted idler pulley that must be removed – it is inside a small hole in the frame
6. Remove the upper engine cover – 4 small bolts
7. Remove side panels and disconnect the spark plug wires
8. Loosen but do not remove the engine shaft bolt underneath the engine pulley and lower it gently – do not remove – you will need a 1.25 socket and breaker bar for someone to hold the top engine bolt while someone works the lower bolt free
9. Start putting on the new lower drive belt on from the engine pulley – you will need to twist the new belt to fit it into the pulley – there are 3 tabs on the frame – make sure that the belt is positioned under each of them – then re-tighten the lower engine shaft bolt to between 35 and 50 pounds using a torque wrench – again you will need a second person holding the large upper engine bolt with a 1.25 inch socket and breaker bar
10. Fish the belt back underneath the frame and to the back of the tractor near the transmission making sure it is positioned on the idler pulley about mid way back correctly
11. Leave the bracket with the double pulley loose for now but put the belt around the lower pulley – the lower pulley will move up the shaft slightly – it has some play
12. Position the smaller upper drive belt on the largest pulley first– the transmission pulley – this is where removal of the right wheel will allow for easier access – have a second person pull the belt through
13. Position the smaller upper drive belt around the upper of the two pulleys of the double pulley assembly – the drive belt from the engine will be on the lower pulley of the two
14. Have one person hold the double pulley assembly with both the lower and upper drive belts in pace on the inside of the battery box while a second person reattaches the assembly to the frame underneath the left side rear wheel using the two bolts
15. Finally pull the smallest pulley located towards the front of the tractor backwards towards the rear of the tractor using the bar and spring assembly that is attached to the frame and put the upper drive belt in place around this smallest pulley
16. Reattach the small bolt near the idler pulley through the hole under the frame that you removed earlier
17. Test by stepping on the gas pedal – belts should tighten around both sets of pulleys as the pedal is depressed
18. Put battery box back in place and reattach leads to the battery
19. Put side panels back in place and re-attach the cutting deck

Mike C., October 2009

I don't think we get these in the UK but they are sure to be similar.....replace the 2 transmission belts with genuine new ones. The engine pulley usually has to be dropped to get the top belt off - it has the usual RH thread, but I use an air gun to shock the bolt loose. If you don't have one you have to find some way of locking the motor.

John, October 2009