X320 mower belt keeps breaking.

[Pibster]

I have a 2012 X320 mower. The dealer swapped out the 48" deck with a 42" deck from a X300 so that it would fit in our building. It has approximately 500 hours of mowing time. I have gone thru approximately 10 or 11 belts over the years, 4 this year alone. The belt normally breaks when engaging the PTO but not always. This last time it broke while mowing light grass. The belt always snaps, no obvious wear marks. The dealer examined the deck and didn't see anything obvious, they wanted to see the deck attached to the tractor but I only took the deck in to the shop. There was some slight play in a couple of the bearings but nothing that would break a belt. This has been going on since year 2 so bearings are likely not the culprit.
I'm wondering if there is a chance that the X300 deck is not compatible with the X320. They always sell me a belt from the X300. Maybe the drive pulley on the engine is a different size on the larger mower? How much tension should be on the belt? At $75-$85 per belt, this is getting too expensive. Any suggestions would be greatly appreciated.

 

[beenthere]

:welcome: to TBN

they wanted to see the deck attached to the tractor but I only took the deck in to the shop

Get it to them.. They accepted some responsibility when switching decks to accommodate you, so seems you owe it to them and yourself to take the unit back to them to go over it.. obvious that you are not detecting what the problem is, so need their help.

Or the alternative, is to just keep replacing belts, as I see it. Not meant to give you more hard time. Wish you well in the fix.

 

[tomplum]

You are paying a premium price for a M154621 belt. Know your dealer likes to bump the price even more than JD list. OEM Deere belts are physically beefier than the aftermarkets so stick with them. I have had a couple of people that had the same issue. Every time the deck is engaged there is shock load on the belt. If the belt gets caught up into a guide, the torque applied at the clutch will snap the belt. Real excessive forward pitch can get a belt pinched. Think of a belt drive like this as pushing the belt through the maze of pulleys rather than being pulled through by the clutch and you will look at this a different way.
Two things within an operator's control is to engage the deck at 1/2 to 2/3 Throttle and to use the mow in reverse feature rather than keep engaging/ disengaging the deck. AT 500 hours, you do likely need to freshen the bearings and likely at least the vee idler in the back if not all.
One other item on these that can occur is that one adjuster at the rear of the deck runs close to the belt. I've only seen one that actually could hit the belt though.

 

[Amvcane]

Pibster,
At what rpm are you engaging the pto?
If your answer is at full throttle, I would try engaging it over an area where there is no long grass, thus no load, and at a low rpm, and then throttle up to mow.

 

[jgayman]

You are paying a premium price for a M154621 belt. Know your dealer likes to bump the price even more than JD list. OEM Deere belts are physically beefier than the aftermarkets so stick with them.

That's for sure. As you can see below he's charging you around 25% over JD Parts list price. Also note there are two other lower cost belts that can be used.

Part Number: M154621
Part Price: 58.82 USD
On Hand: 7 Check Other Stores
Description: V-Belt - V-BELT
Package Quantity: 1

Alternative Part
A-M154621 V-Belt - JOHN DEERE BELT - 46.14 USD
B1M154621 Belt - BELT - 1/2" X 146.244" KEVL - 52.12 USD

 

[Pibster]

Pibster,
At what rpm are you engaging the pto?
If your answer is at full throttle, I would try engaging it over an area where there is no long grass, thus no load, and at a low rpm, and then throttle up to mow.

I have been engaging the deck at full throttle. It does sometime break while mowing short grass. The end of one of the deck leveling bolts was about a 1/4" from the belt so I cut that off hoping it would fix the problem, apparently not the problem.

 

[Pibster]

My dealer is charging me $80.81 (Cdn) per belt plus tax. Not the Kevlar one either.

 

[tomplum]

The Kevlar label is on the aftermarket belt. The OEM Deere belt may very well be Kevlar if they felt it best. There are several aftermarket options out there. I have 3 that I deal with. The closest in girth was the Stens. The AE I have no experience with.

 

[Diggin It]

I despise the way the belt slaps on my X-300 when I engage it. I've tried at less than half throttle and I get the same thing, but it tries to stall the engine too. I switched to an aftermarket Kevlar belt I get for under $20, but I've snapped a few of them too. Last time a couple of months back, I went through the deck and found a few things that might have been a bit out of alignment and one idler pulley that was noisy. I guess I'll see if that did any good or not.

I don't understand why there isn't a soft start mechanism of some kind to relieve that initial tension.

 

[FortClatsop]

If you haven’t already an inter web search for “X300 belt breaking” brings up lots of stuff on lots of forums and YouTube. I think it’s specific to the X300 and the 42” deck. I remember seeing that when I was looking for info on my X324.