finish mower belts

[j845125]

I have a Del Morino finish mower, 91". One side always throws the belt. This is the 2nd finish mower i've had in 15 years and never had a problem like this. I've replaced bearings, leveled the pulleys, but one belt always starts jumping, rolls over and jumps off. Does anyone have any suggestions?

 

[wushaw]

Make sure it is the correct belt for that installation. Having a belt that "fits" is not always the correct one.

 

[RoyJackson]

May be wobble in one of the pulleys. Try to rotate the belts and observe any movement in the pulleys at the drive pulley and the driven pulley. It wouldn't take too much at high RPM.

How do your belts drive? Do you have a double pulley at the center that drives one blade with belts off it to each side? How much deflection do you get on the belt(s)?

Another thing you could try is getting the mower up (on jackstands), disconnect the PTO shaft from the gearbox and have someone rotate the gearbox. You could watch the belts from the bottom (not under the mower though!).

As wushaw wrote...are you sure you've got the correct belt installed?

 

[Arkaybee]

Check for proper functioning of the idler/tensioner pulley. Maybe it is not freely pivoting in order to maintain proper tension. Or, the spring on the tensioner pulley arm is missing or weak. This will allow excess slack in the belt. HTH.

 

[Shadowjack]

I have a Del Morino finish mower, 91". One side always throws the belt. This is the 2nd finish mower i've had in 15 years and never had a problem like this. I've replaced bearings, leveled the pulleys, but one belt always starts jumping, rolls over and jumps off. Does anyone have any suggestions?

I think I have same deck. 90-91", 5 blade, with 2- B120 belts. Right half of mower belt was jumping. Belt would ride up on Idler lip. I machined 3/16" off idler
for better alignment, also any rough bearings will make belts wipe. My deck works good know.