Help needed with Scag deck belt - slips off.

Discussion in 'Mechanic and Repair' started by Jason Pallas, Apr 17, 2006.

  1. Jason Pallas

    Jason Pallas LawnSite Bronze Member
    Posts: 1,325

    I'm working on a Scag 61" Tiger Cub w/Advantage Deck. The deck belt keeps coming off each time the PTO is engaged. I tried engaging the PTO at all different RPMs and I've checked all spindles and pulleys for any wobble, sticking, etc. Belt is also fine. Everything is fine - belt rotates fine when I put it on and rotate it by hand - but the second the PTO engages - the whole thing comes off. I believe I have it on right - checked it against the diagram that's written on the deck and the tension on the belt is good too. This one has me stumped. Please help me.
  2. lucforce

    lucforce LawnSite Member
    Posts: 223

    Is there any physical damage to the belt?

    Are belt guides in place?
  3. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Once a belt rolls off one time under tension it tweaks the inner cords that will give it a slight twist then it will hardly ever stay on. I would suggest a new belt and check pulley alignment and belt guides as mentioned, Engage around 1/2 throttle then once to speed give it full throttle.
  4. Jason Pallas

    Jason Pallas LawnSite Bronze Member
    Posts: 1,325

    Belt appears to be in good shape - some slight signs of wear. There are no belt guides that I can see.

    Restro - the guy said that it ran fine back in Jan - after he changed the spindle, he ran it for about 20 minutes. It ran fine. However, when he re-engaged it, it ran for about 3 minutes and then slipped off. Now it slips off immediately upon engagment at any RPM. All pulleys look alingned well.
  5. Jason Pallas

    Jason Pallas LawnSite Bronze Member
    Posts: 1,325

    Thanks - it was the belt. I would have never thought it - it looked pretty good. Learn something new everyday - especially from Restrorob - Thanks again!!!
  6. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    No problem Jason, Glad ya got it straightened out.

    TURF DOCTOR LawnSite Silver Member
    Posts: 2,138

    He is right we had the same problem with a mid mount grasshopper ever thing seem to be normal the belt got twisted some how,we changed the belt and no problem it hurt though to throw a high dollar belt in the trash.:dizzy:
  8. JamesVaughn3rd

    JamesVaughn3rd LawnSite Member
    Posts: 7

    So I know this is an ancient thread but instead of starting a new one, my issue is similar.

    I was mowing the other day and went up a hill and I believe my deck drive pulley hit the ground and it popped off. Belt came off as well.

    I bought a new belt since the old one got chewed up and put it on. Got everything lined up and went off. After mowing about 100 feet, I noticed that the drive pulley was slipping out and the belt was about to slip off. I placed it back into alignment and after another 100 feet the pulley slid out again and belt popped off.

    So my question is, how does the drive deck pulley work? I know it has this split tapered hub that I thought tightened itself when you tightened the three bolts. Honestly I cannot get them any tighter so I am thinking that I'm missing something in making the hub stay put. Any help would be great. Thanks.

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