Burnt belt

13AV60KG011 - Troy-Bilt Bronco Lawn Tractor (2009)

Just put a new main drive belt (954-0468) on this mower. The top short one that only drives the transmission and variable speed pully and the one small idler pulley. (The spring connects to the top of the idler pully on the right (passenger side) and connects to a bolt on the left side) The first one was burnt on the outside. This one, has only been on for a couple of hours and can see signs of it doing the same thing.

Also, it keeps jumping off. Everything is lined up. The spring may be a little week. But not so week that I can reach in and take it off by hand. I use a long thick wire, loop it in the end of the spring, then stretch it over the stud. Then screw the nut back on.
Anyone ever run into this before.

Also, the belt guild on the small pulley, should it be facing towards the front of the mower?

Belts only burn if they are running against a pulley that can not turn at the same speed , or they can not turn and are against a turning pulley.
And yes the belt retainer goes to the outside of the pulley and faces forward.
IT was a latter addition and stops the belt jumping off when you flick your foot sideways off the pedal.
It should be very close to the pulley.
There are 2 almost identical drives, one uses 4L ( 1/2" ) belts and the other uses 5L ( 5/8" ) belts
If you got the correct belts they should appear too shallow ( top to bottom ) for their width.

Now where on the belt is the burning happening ?

bertsmobile1 said:

Belts only burn if they are running against a pulley that can not turn at the same speed , or they can not turn and are against a turning pulley.
And yes the belt retainer goes to the outside of the pulley and faces forward.
IT was a latter addition and stops the belt jumping off when you flick your foot sideways off the pedal.
It should be very close to the pulley.
There are 2 almost identical drives, one uses 4L ( 1/2" ) belts and the other uses 5L ( 5/8" ) belts
If you got the correct belts they should appear too shallow ( top to bottom ) for their width.

Now where on the belt is the burning happening ?

Click to expand...

If they should appear too shallow, then I should've went with the 1/2" instead of the 5/8th, that the diagram shows.

Where's the belt burning? On the outside. Me and my buddy looked all over the place, and nothing seems to touch it. Even when you press the foot pedal to engage it. On thing we did try, was a stouter spring. That was THE wrong thing to do. The belt slipped off within 10ft.

The big pulley is slightly out of line with the idler pulley. Just slightly. It's bracket swivels. The bolt on the swivel is tight, but there is a little play in that bracket, where it swivels.

AS you can see from the above, an L section belt is shallower from to to bottom than a std A or B section belt would be and are used on sliding sheave ( varidrive ) pulleys
And conversely a V section belt is deeper from top to bottom than a std A or B section belt would be and are used by Murray as a deck belt.

If you have bought a std A or B belt then they will cause you grief and not last as long as a 4L or 5L would.

The pivot point on the tension arm flogs out oval over time and you can replace it or weld the hole & reshape it round but generally some flop there does not cause grief.
So your top belt is rubbing and burning on the outside ( 5/8" ) side where the writing is .
If that is the case then the sliding part of vari drive pulley is stuck or the whole pulley is running too close to the side of the mower.
They use the side frame as a belt retainer which is why you have to remove the whole pulley to change the belt .
Try putting it up on 4 jack stands so you can get under there with the engine running ( deck removed ) and watch what is going on.
If you pull both of the seat switch wires off you can then work the motion pedal while watching the double pulley.
AS you push the pedal down you should see the lower belt running deeper in the double pulley and the top belt running further out.
This should be a very smooth motion.
As the top belt runs further out on the double pulley you should see the idler pulley pull back and stretch the spring.

Try doing this with the engine running slow so you can see what is happening.
You can remove the battery, tie the seat to the steering wheel ( or remove it ) start the mower using jumpers and have our friend watching the belt from above.

Exactly how did you replace the belts, which pulleys did you remove / loosen to do it.

I just removed the tension spring, and the guide off the idler pulley, and it came right off. Put on the new one, in the same reverse fashion. On the big pulley, it was a little tough getting it between the pulley and the side wall. I just started it in the groove, then turned the pulley.