Mowing 955 belly mower belt comes off

Bjohn · May 24, 2005

I have a 1991 955 with a 60" belly mower. When I turn off the pto it throws the belt off the center pulley, ANY SUGGESTIONS?

prosperity · May 25, 2005

Are you letting your engine idle before disengaging the PTO?

Bjohn · May 25, 2005

No I didn't idle down this is the first I've used the pto for anything. I'll try this next time . Do you know how much throttle is recommended while mowing?

prosperity · May 26, 2005

My basic rules are:
Engage and disengage the PTO at idle only.
Mow at full throttle.

If you find the tractor stalls when engaging, kick the throttle up just a little next time.
Disengaging at high throttle could be the cause of the belt jumping. Also, its hard on the PTO brake.

Bjohn · May 26, 2005

I tried shutting down the pto at idle speed. The first couple times it shut down without throwing the belt but after mowing I slowed it to idle and waited for it to slow before turning it off and it threw the belt off again. I wonder if a stronger spring would help?

prosperity · May 27, 2005

Ok - now we'll have to look further into it.
If possible, take the deck out from under the tractor.
Remove the covers over the belt/pulleys.
Make a close inspection of the belt/pulleys/springs.

With the belt on, slowly turn everything and look for anything irregular - pulleys wobbling or even debris built up under the covers and pulleys. While doing this, also closely inspect the belt. A stretched/damaged belt can do this. A worn belt is the most likely cause.
Try removing the belt and pay attention to the spring tension. It should take quite a bit of effort to get the belt off one of the pulleys.
Also while you are at it, check the PTO shaft for lubrication and/or damage.
After the belt is off, check that the pulleys spin freely and don't wobble at all.
If all "looks" ok, I would get a new belt. Replacing the spring isn't a bad idea - will probably be pretty cheap.

When putting everything back together, be sure to grease all the spindles. I grease my deck fittings every 25 hours.

Let me know how you make out. I'm going to visit my JD mechanic next week (Tues or Wed) and I can pick his brain some after you check the above.

beenthere · May 27, 2005

In addition to what 'prosperity' says, check the idler pivot point (the arm where the spring is attached). If this point is tight, rusted, or just out of grease, it may not be reacting fast enough and be contributing to the cause. However at this point, the belt may also have a nick in it and need replacing as well.
It certainly wasn[t designed this way, so something is wrong. Good luck finding out what it is. /forums/images/graemlins/wink.gif