Craftsman LT 1000 Mower belt installation fail

Mower belt install fail – Craftsman LT 1000


The mower belt failed on my Craftsman LT 1000. I tried to take a shortcut by not completely removing the deck. I put the belt over the belt guide for the idler pulley  which almost wrecked the belt instantly. 

My yard is 2 1/2 acres. About an acre of that is woods which I mow. There were a lot of storms which resulted in a lot of small branches on the lawn and in the woods. 

One of these branches got in between the belt and a pulley causing the belt to fail. I was hoping to finish cutting so I rushed the belt replacement. Fortunately I keep a mower belt in stock. 

I didn’t want to completely remove the deck so I loosened up the left lift bracket. That allowed me to thread the belt correctly on the pulleys. … Well, almost correctly. 

I made sure that the belt was under the brake arms for the two blade pulleys. 

Belt install Fail

Since the deck was still on the mower, I couldn’t see the pulleys. I thought I had it installed properly. What I didn’t realize is that there are two belt guides on the idler pulley that is operated by the mower lever.

You can see below that the belt is under one guide correctly (arrow) but is incorrectly placed over the other guide (circle)

Arrow = correct | Circle = wrong

Warning Signs

Haste makes waste. It had been a hard day of job searching and I had just cut about 2 acres of grass. It should have been obvious before I started the tractor that I had the belt installed incorrectly:

  • The belt was too difficult to get on the engine pulley. It is tight but this indicated that there was a problem. I ignored that warning
  • When I started the tractor up, the blades were spinning with the mower lever disengaged. I ignored that warning. 
  • When I tried to engage the blades, it was very difficult to move the lever up. I attributed it to a new belt and ignored the warning. 
  • I ran from the garage to the edge of the woods. I noticed a slight burning rubber smell. This time I did NOT ignore the warning. 


I ‘disengaged’ the blades and returned back to the garage. This time I decided to pull the deck. As soon as I pulled the deck out from under the tractor I realized my mistake. I said a few bad words at that point. 

The belt got beaten up a bit but I figure I might get to the end of the season out of it. 

As I looked more closely, I saw that the pulley brake for the left blade pulley was not disengaging. I’ll do a separate post on that. Putting the deck back on the tractor without fixing the blade break seemed like a bad idea. The brake are would fail rather quickly. Also, the friction would make the pulley hot and that would probably shorten the belt life significantly. 

The right and left brake arms are the same so I ordered a pair along with a spare belt. 


Today’s Lessons:

If the belt and mower lever don’t seem right, recheck your work.

If you smell rubber burning, you screwed up.

It is possible to replace a mower belt by only disconnecting the left lift bracket but you need to be careful with the belt guides.

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