312-8 Deck Drive Belt Jumping

[Houdini#48 0]

My belt keeps jumping off the deck and PTO. Upon closer inspection I noticed I had a carriage bolt fall out from my 37" side discharge deck. Thought that was the problem. Put a temporary replacement in until the new one arrives, put on a new Wheel Horse brand belt, read the belt tension adjustment guidelines and the darn thing still jumps off upon PTO engagement. What in tarnation am I doing wrong? Is it mower level adjustment, traction lift bar-trunnion & lift rod adjustment or transport level stop adjustment. Can there be any more deck adjustments? I'm just wanting to mow my lawn.

[GlenPettit 1,717]

You've done everything exactly right.

Somewhere there is a little something out-of-whack.

-- There should be about 1/2" deflection in the belt for the correct tension, (in the front "mule" to deck section of the belt).

-- Sounds crazy; but are all four of your tires all inflated to the same 10 psi.

-- Touch all bolts, pulleys, blades to see is everything is snug/tight, with power off.

-- Compare the Owners Manual Photos with your deck, the trunnion & life rod positions.

-- Does this happen right away; just setting there on the drive, on level light grass/ground, or just in tall thick grass?

We're all here to help,

And sometimes it seems to just take a little Magic! (Re: Your Screen Name)

[cheesegrader 433]

Check your motor mounts.

Mounts from motor to plate, and plate to frame.

I had the same problem when I got mine a few years ago, and I did all the things you tried.

I finally realized that the motor was twisting on it's mounts on PTO engagement just enough to throw the belt if I hit a bump.

Found the loose bolts between the plate and frame, tightened them (with much cursing and a little loss of skin off my knuckles)

and the problem stopped.

[Sparky-(Admin) 23,158]

Any chance we could get a picture of your setup?

Mike...........