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Belt slips off pulleys because idler pulley that tightens belt does not line up with engine pulley & I see no adjustment. Belt is in good shape. What do you guys think I need to do? This is a Cub Cadet with a Kohler eng.

You need to give us more info. These would help. Tractor model, age of belt, drive belt or PTO belt, is it an OEM belt, how long is this been going on, age of the tractor, when was the idler pulley changed last. We are not standing next to you to see what's going on, and with 230 posts you should know that our ESP has been done for sometime now. Paint us a better picture.

Rivets said:

You need to give us more info. These would help. Tractor model, age of belt, drive belt or PTO belt, is it an OEM belt, how long is this been going on, age of the tractor, when was the idler pulley changed last. We are not standing next to you to see what's going on, and with 230 posts you should know that our ESP has been done for sometime now. Paint us a better picture.

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It's a Cub Cadet 42 " cut Model #SV530S, serial #3710625323 & built in 2007. Mower belongs to a neighbor so I cannot answer the other questions. I don't see him often. I don't see how a new belt or OEM helping my problem. It's the belt that powers the two ZTS transmissions. The pulley that tightens the belt does not line up with pulley on engine shaft. The belt from engine pulley goes into the pulley that tightens the belt at about a 30% angle. The pulleys are about 3 inches apart. At that angle the belt climbs out of the pulley. Hope this helps.

With an OEM belt in good condition, a 30 degree angle may not be a problem. At that angle you should be able to see any wear or distortion where the pulley is mounted. In many cases not using a non-OEM belt will cause the problem, as will belt wear. Second, cause would be a worn pulley bearing which will cause the belt to ride incorrectly. Finally, is it routed correctly and is the tension spring pulling in the proper direction?

Rivets said:

With an OEM belt in good condition, a 30 degree angle may not be a problem. At that angle you should be able to see any wear or distortion where the pulley is mounted. In many cases not using a non-OEM belt will cause the problem, as will belt wear. Second, cause would be a worn pulley bearing which will cause the belt to ride incorrectly. Finally, is it routed correctly and is the tension spring pulling in the proper direction?

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Thanks for answer Rivets, I will get a new OEM belt & take pulley off & check bearing. Thanks again.

Rivets is correct But also look at the arm it is on. It could be bent and need to be streightened.

BlazNT said:

Rivets is correct But also look at the arm it is on. It could be bent and need to be streightened.

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The arm looks like its not bent. The pulley & bearing look good, does not wobble. Thanks BlazNT

I'd suggest finding a similar model mower and taking a look a the belt/pulley alignment on it. I can't imagine the design of the mower having that much misalignment and expect the belt to stay on and last any time at all.

As this is not your mower, assume that i has been worked on by shaved monkeys.
Check that the engine pulley is in line with the drive pulleys.
If not then chance is it has been replaced at some point in time or is just not tight.
Also check that the idler is on the right way around.
many have spacers on them to get them to line up and most can be fitted wrong way round.
Also verify that the pulley is the original Cub part.

When it comes to idlers, I buy the raw pulley with bearing then fit my own bush, or refit the bush that was in the original one.
By doing that I have knocked over 100 different pulleys out of my spares inventory as they were all pulleys that were the same sizes with different bushes fitted.
Pulleys that are designed to be close but out of alignment usually are wide with long flanges to allow the belt to run sort of spirally around the pulley.
If they are flat idlers they can wear into a cone shape and when they do the belt will run strait off the pulley.

Is the problem pulley a fixed or moving pulley and flat or V ?


If you can go to the cub web site, pull down the parts list and post the actual part number it will be a big help.