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Deck Belt Question

Discussion in 'Lawn Mowing' started by tothmow, Jul 2, 2007.

  1. tothmow

    tothmow LawnSite Member
    Posts: 12

    I own a 48" Exmark Lazer CT. I bought it used with 150 hours for home use (2 acres).

    I am not very mechanical so this is probably a simple question.

    I threw the deck belt yesterday. The engine was cold and sputtering when I engaged the PTO and it stalled and threw the belt. I lifted the top of the deck, saw the diagram showing how the belt should feed through the pulleys, pulled on the belt to get some slack and placed it back on the pulleys.

    My question is how much tension should be on the belt? It seemed too easy to merely pull on the belt with one hand and feed it around the pulleys with the other. There is tension on the belt, I am just not sure if it is enough tension. Maybe this is normal. I have never worked on a zero-turn mower before and that is why I ask this question.

    For additional information, after I fixed the belt I reached under the deck and rotated one of the blades by hand. The other blades rotated as well but only sporatically...they didnt follow the rotation of the blade I was turning exactly. In other words, the belt was loose enough such that it slipped somewhat when I rotated a blade by hand.

    I checked my owners manual and all it says about the deck belt tension is "self-tensioning, no adjustment necessary".

    I mowed after fixing the belt and it seemed to mow ok, but I couldnt tell if the belt was slipping more than it should be on the pulleys or not.

    Thanks for the help!
  2. Mark in MD

    Mark in MD LawnSite Senior Member
    Posts: 322

    I'm not familiar with your machine, and mine are not self tensioning (old Bob-Cat mowers). When I put my belts on, I know they have to be fairly tight, tight enough so that they don't slip. I also know that they can't be too tight, or the belt will wear out real quick, or the blades won't stop spinning after disengaging.

    Also, they frequently need to be retightened a little because the belts get stretched out slightly after a few hours use.

    Hope this helps some.
  3. MOturkey

    MOturkey LawnSite Silver Member
    Posts: 2,757

    Don't know diddly about the Exmark setup, but I'm assuming it has to have a spring, or springs, to keep constant tension on the belt, like my Gravely has. Are you sure that you haven't broken, or lost a spring, or perhaps one has come unhooked?
  4. tothmow

    tothmow LawnSite Member
    Posts: 12

    MOturkey and Mark in MD:

    Thanks for the feedback. I checked the belt again and noticed that the belt had slipped off one of the spindle pulleys and the belt was slipping along the bottom of the pulley.

    I put the belt back in the proper place and now there is good tension on the belt. Hopefully I didnt damage the belt too badly by running it for 1/2 hour or so along the bottom of the one pulley.

    Thanks for the help! If the belt breaks now at least I will know the cause (my stupidity).
  5. screensnot

    screensnot LawnSite Member
    from MI
    Posts: 86

    How did it cut with the belt like that? :laugh:
  6. Vikings

    Vikings LawnSite Bronze Member
    from canada
    Posts: 1,667

    I was just looking at my belt yesterday on a Toro 36 and I thought it was very loose. But once I put the blade engagement lever on (whatever it's called) I had about 1/2 of play and that was normal.
  7. bobcat175

    bobcat175 LawnSite Senior Member
    Posts: 377

    I set mine to about 1/2 - 3/4 of deflection in one direction at the longest run of the belt. You should also check the height of the spindle pulleys. Make sure that the belt is turning in the middle of the pulley and that the belts are all level. I would also check the idler pulleys (springs,tension, etc). If you didn't adjust anything then it might happen again....I'd find out why it threw the belt in the first place...better to test it in the garage than have it happen again in the field.
  8. Runner

    Runner LawnSite Fanatic
    Posts: 13,496

    It is not uncommon on many mowers that if you turn the blade by hand, that it will slip and cause the other blades to only turn in "lumps" if even at all. Sometimes, it feels almost like a compression stroke - even though the motor isn't turning at all.
  9. tothmow

    tothmow LawnSite Member
    Posts: 12

    The mower actually cut OK for the 1/2 hour or so that I was running with the belt slipping along the base of one pulley. That blade must have been turning to some extent as it was cutting grass although there were a few high spots where that blade was not keeping up with the other two.

    The big difference was the sound generated by the deck...much lounder than normal which must have been due to the loose belt. Also, when I pulled the deck cover there was some black dust around the pulley which must have been the base of the pulley eating into the belt. The belt still looks ok but I went out and purchased a spare belt just in case (I am sure I will need it eventually).

    Thanks for the feedback.

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