BX2660 MMM belt wants to climb up left pulley

[nepa]

My 09 BX2660 with 270 hrs and 60 inch MMM is giving me problems with the mower belt. Last month, the belt climbed half way up the left pulley (as I am seated) and wore through the plastic pulley guard. Everything was lubed as per specs. The tensioning arm has a very strong spring but otherwise moves freely. Nothing looks out of place, the pulleys turn without binding, and there is no debris on the pulleys or elsewhere that might pry off the belt. It started coming off again today. It is hard to imagine how this is happening with the deep mid groove in the belt. The long span between pulleys at the rear of the mower has a little bounce when running but I would not call it excessive. Has anyone encountered a problem like this?

 

[Midniteoyl]

How old is the belt? Belts with broken strings tend to climb and/or flip.

 

[Grandad4]

What is the condition of the belt? If most of those 270 hours were spent mowing, it may be time for a replacement belt. Mine never wanted to jump off the pulleys but stretched enough over time that there was some slippage. New belt made a world of difference.

 

[nepa]

The belt looks terrible now. I've been seeing several part numbers for the belt on my RCK60B-23BX mower. What part number would be correct? Does Kubota want to confuse us with multiple part numbers that are compatible? Thanks.

 

[Leejohn]

My parts call for only one belt for the 60", K5763-34710. Check the 4 bolts that hold the pulley to the holder, do it with the belt off, holding blade and see if there is any movement in the pulley.

 

[Panik]

Interesting.... I just had this problem after replacing my belt. I replaced the original belt after an ill-advised trip mowing down the trails that resulted in a piece of branch getting lodged in under one of the belt covers and chewing up the original belt.

The BX has right at 200 hours and the new belt walked up the rim of the left pulley after about 2 hours use and chewed up the brand new belt cover I had purchased. Oddly, I rotated the belt until is was tracking properly and proceeded to mow for another 2 hours without issue. Wish I could provide an answer. Without a repeat performance I'm chalking it up to something with the belt alignment that happened during replacements.

 

[nepa]

Thanks for the number Leejohn. That was one of the numbers that I found along with K5763-34712. I will check the 4 bolts and till I get the new belt I am going to experiment with flipping the belt over. I was only mowing sparse dry grass today for only 15 minutes when the belt moved up. Panik, why did you replace your belt? This happened with your new belt?

 

[TripleR]

My parts call for only one belt for the 60", K5763-34710. Check the 4 bolts that hold the pulley to the holder, do it with the belt off, holding blade and see if there is any movement in the pulley.

That was our problem. Also check for bad bearings, happened once too; seems one of our kids was allergic to grease guns.

 

[CHIEF640]

I had the same problem with my 2009 BX2360, installed a new belt and it did the same thing again. I replaced all three pulleys . When the new pulleys came I noticed they had a plate welded to the bottom side to make them stronger and keep them from bending . Since I replaced them I have had no problems. All three of the original pulleys were bent causing a lot of up and down movement. The part number for the pulley never changed but they must have had problems and reinforced them.

 

[nepa]

All of these answers make sense and are good to know. Thanks.