Gravely Belt comes off

[bob]

The belt (mule?) that drives the blades on my Gravely 272 (31hp turo diesel) has been jumping off the pullys all year long. It comes off when the PTO is engaged. It finally broke and I put on a new belt and 3 new tension springs. Its been good for about 2 weeks until today when the belt jumped off again. I engaged the PTO at the lowest throttle setting and it came off. When my son engages the PTO he uses 1/2 throttle and it hasn't come off for him yet.Any ideas what to look for? thanks

[Restrorob]

Bob,

I engage ALL unit PTO's at half throttle, Once the blades reach this rpm give them full throttle. Doing this causes less belt deflection (slap) and less chance of the belt jumping off.

Check your owner's manual for proper PTO engagement.

[Juan_Deere]

Although the manual for my Gravely does state to start the PTO at 3/4 throttle, it sounds like your son already found what you should be looking for. Start it at 1/2 throttle like he does. If it was popping off while actually mowing, I would start looking for other causes. Right now, it just seems you have to follow the 1/2 throttle routine.