Mower deck belt jumping off again

[jpilk99]

Hi folks,

I have a 2011 Husqvarna LGT 24K54 rider and love it ...when it's not giving me fits. And I realize that machines don't give fits, owners who aren't clever enough to keep em' running proper are the issue .

I had a lengthy post at the end of last season where the mower deck belt kept jumping. Lots of good inputs/questions around pulleys, tensioner, etc. and while I got all new spindles, a new tensioner, certainly new belt(s), I think the issue ended up being that the "pitch" of the deck was not correct. I know the front needs to be 1/8" to 1/2" lower than the rear and ...after addressing that, it seemed to work well. For a while.

Now it's doing it again. I bought a new belt (not OEM) and thinking that was a mistake; either too wide or a bit too long. I checked all bearings/spindles and all seem fine - no slop, same height, etc.

I guess my big question is this: If I start all over with getting on a flat surface, measure height of blades - front to back - off the ground, as well as side to side to make sure she's level, I wonder about where "top dead center" is, or where Husqvarna expects me to start ...ground zero? If I put the deck adjustment at the bottom, what height should things be off the ground? Where is the starting point for that front "arm" that attaches to, and 'lifts' the front of the deck, where should I start with that? I"m wondering if I'm starting TOO HIGH or TOO LOW with that front arm, or the 2 rear arms, to then start measuring the height of the blades, etc.

It's crazy but, I put a new belt on, can see that the front is nicely lower than the rear, (almost a 1/2"), and I can go Maybe 50' before the belt jumps. I do have more success if I mow with the deck high off the ground, but, ...I like a nice flow, low cut, of the grass.

Please help. Thank you!!!

Jay

 

[Leejohn]

Belt guide pin are bent and out to far from pulley. Could also be broke off and missing.

 

[jpilk99]

Belt guide pin are bent and out to far from pulley. Could also be broke off and missing.

Thanks so much for quick response, Leejohn. Please forgive my ignorance, but, what is"belt guide pin"? Internet search doesn't show me anything that I see on my deck/tractor. Is it that "arm" bolted to top of pivoting tensioner pulley that ducks down a hole in tensioner arm? I've been wrestling that thing for years. Belt jumps, it gets ...muckled. Bend it back into place, ...belt jumps, it's gets moved. Bought new one, same story.

Thank you!

 

[tomplum]

It would be good to link your old post to this. In regards to your leveling question, most times on a Husqvarna deck when you place the front rod in the hole you will have to lift the front of the deck a tad. Set your tire pressure and measure from the blade tip cutting edge in the position that you normally cut in. Reduce the forward pitch to a 1/4" if you are loosing the belt. (587686701) You can raise the deck at its highest setting to where you are below the frame by at least 1/4" if you wish. It would be nice to know which pulley the belt comes off. Coming off in 50'- there is something definitely wrong with the deck. I've added an extra guide at times for those that loose the deck at the tensioner. Just buy the same guide and mount it where you think the belt would PUSH off. Think not of the engine pulling the belt through the pulleys, but of it pushing the belt through. That change in mindset helps solve these kind of issues.

 

[jpilk99]

It would be good to link your old post to this. In regards to your leveling question, most times on a Husqvarna deck when you place the front rod in the hole you will have to lift the front of the deck a tad. Set your tire pressure and measure from the blade tip cutting edge in the position that you normally cut in. Reduce the forward pitch to a 1/4" if you are loosing the belt. (587686701) You can raise the deck at its highest setting to where you are below the frame by at least 1/4" if you wish. It would be nice to know which pulley the belt comes off. Coming off in 50'- there is something definitely wrong with the deck. I've added an extra guide at times for those that loose the deck at the tensioner. Just buy the same guide and mount it where you think the belt would PUSH off. Think not of the engine pulling the belt through the pulleys, but of it pushing the belt through. That change in mindset helps solve these kind of issues.

Thanks Tom.

Here's the link to the previous post: https://www.tractorbynet.com/forums...127-brand-new-mower-deck-belt.html?highlight=

When you say to "measure the blade tip cutting edge in the position that you normally cut in", there isn't enough room to get under the deck and measure . Don't understand your other comment about "You can raise the deck at its highest setting to where you are below the frame by at least 1/4" if you wish".

I would say it's jumping off at that tensioner pulley with the guide on it, because there's where it seems to be all bungled-up after jumping.

Interesting, your initial comment about "you will have to lift the front of the deck a tad" after placing the front rod in the hole - I don't have to do that, so obviously that means the rod is too long, and I need to shorten.

 

[tomplum]

A common complaint that I hear is not being able to cut high enough. Over all HOC is limited by tire pressure (14 front 10 rear is common), how far the rear of the deck can go and the amount of pitch. It is apparent by your comment on leveling that that isn't a concern of yours. So yes, raise the deck where you can work with it. Remember that if you are cutting very low, grabbing a high spot with a blade momentarily slows belt travel at that spindle. Remember that the deck is not only wide, it is deep to where the front of the center blade to the rear of a side blade creates a big triangle. Tilt that triangle forward from an increased pitch it seems to exaggerate itself. Remember the rear doesn't change. It is common with the single rod suspension in the front that the little bracket under the axle gets bent increasing the pitch. Especially with more deck for weight and width to hit something with.
I'm still thinking something is askew here due to how quickly it comes off. This is one of the few decks that I work on that have such a great deck belt life that the belt can run practically the life of the tractor. Be sure that your anti sway bar is on in the rear, that your center arms are secured at the rear deck brackets and not coming loose.

 

[jpilk99]

It would be good to link your old post to this. In regards to your leveling question, most times on a Husqvarna deck when you place the front rod in the hole you will have to lift the front of the deck a tad. Set your tire pressure and measure from the blade tip cutting edge in the position that you normally cut in. Reduce the forward pitch to a 1/4" if you are loosing the belt. (587686701) You can raise the deck at its highest setting to where you are below the frame by at least 1/4" if you wish. It would be nice to know which pulley the belt comes off. Coming off in 50'- there is something definitely wrong with the deck. I've added an extra guide at times for those that loose the deck at the tensioner. Just buy the same guide and mount it where you think the belt would PUSH off. Think not of the engine pulling the belt through the pulleys, but of it pushing the belt through. That change in mindset helps solve these kind of issues.

How do you "add extra guides for those that loose the deck at the tensioner"?

 

[Richard001]

jpik

It's idler bounce. As you say, it only happens when you are mowing in the lower setting, thus placing more force on the belt. As the blades engage the grass and/or some heavy clumps of grass, the belt stretches and then when the load is less, the belt relaxes. This will cause the idler to bounce as at one moment the belt is longer and then the next moment the belt is sorter so the idler has to move to accommodate this change in belt length.

As Tom has said, extra guides will help, but the real reason is idler bounce.

A stronger spring will help, and frankly I'm surprised that you are balking at getting a new spring, with all the issues you are having.

Some kind of shock absorber is required to limit the idler bounce. Actually the idler should never move away from the normal position. Yes it can go in to tighten the belt, but is should never move out to make the belt loose.

Here is my suggestion. Find a way to put a piece of rubber that has some give to it, say a cut out piece of bicycle tire. Bolt the rubber piece in position so it is just touching or at the most a 1/4" away from the idler arm when in the normal position. Just to make this a little clearer, the rubber piece should be positioned so that the idler arm will be limited in it's movement to make the belt loose.

If you had a high speed camera, you would not believe how much the idler pulley moves. And what causes the idler arm to move, belt stretch.

Richard

 

[jpilk99]

jpik

It's idler bounce. As you say, it only happens when you are mowing in the lower setting, thus placing more force on the belt. As the blades engage the grass and/or some heavy clumps of grass, the belt stretches and then when the load is less, the belt relaxes. This will cause the idler to bounce as at one moment the belt is longer and then the next moment the belt is sorter so the idler has to move to accommodate this change in belt length.

As Tom has said, extra guides will help, but the real reason is idler bounce.

A stronger spring will help, and frankly I'm surprised that you are balking at getting a new spring, with all the issues you are having.

Some kind of shock absorber is required to limit the idler bounce. Actually the idler should never move away from the normal position. Yes it can go in to tighten the belt, but is should never move out to make the belt loose.

Here is my suggestion. Find a way to put a piece of rubber that has some give to it, say a cut out piece of bicycle tire. Bolt the rubber piece in position so it is just touching or at the most a 1/4" away from the idler arm when in the normal position. Just to make this a little clearer, the rubber piece should be positioned so that the idler arm will be limited in it's movement to make the belt loose.

If you had a high speed camera, you would not believe how much the idler pulley moves. And what causes the idler arm to move, belt stretch.

Richard

Thanks VERY MUCH Richard. Great inputs/ideas.

Not sure where - how - you got some impression I'm averse or "balking" at getting a new spring. I'll buy a new spring tonight. That makes a lot of sense. (I actually bought a brand new spring at the end of last season... Just remembered that when I went out to take a picture of the deck).

I'm pretty sure I bought a new idler arm "setup", the pivot-arm and the pulley that moves in and out. i have a new spring and 'retaining arm' coming soon.

Very interesting comment about keeping the belt loose - I would have thought the exact opposite, keep belt taught/tight so that it doesn't jump, but, you make a great point about when the blades engage thick grass, belt tightens, blades then spin free and belt loosens ...

Almost seems like I should try and have that pulley that adjusts forward, pivoting on the tensioner arm, to stay "back" ...so that the belt stays loose, right? Just don't know how to do that. Where were you thinking I'd bolt the piece of rubber (see attached photo). Why not just use a ...softer spring? Just scared about this because, if I throw my BRAND NEW belt, it will stretch and become closer to junk. I've bought probably 3 or 4 belts in the last few months... :-(

 

[jpilk99]

Thanks VERY MUCH Richard. Great inputs/ideas.

Not sure where - how - you got some impression I'm averse or "balking" at getting a new spring. I'll buy a new spring tonight. That makes a lot of sense. (I actually bought a brand new spring at the end of last season... Just remembered that when I went out to take a picture of the deck).

I'm pretty sure I bought a new idler arm "setup", the pivot-arm and the pulley that moves in and out. i have a new spring and 'retaining arm' coming soon.

Very interesting comment about keeping the belt loose - I would have thought the exact opposite, keep belt taught/tight so that it doesn't jump, but, you make a great point about when the blades engage thick grass, belt tightens, blades then spin free and belt loosens ...

Almost seems like I should try and have that pulley that adjusts forward, pivoting on the tensioner arm, to stay "back" ...so that the belt stays loose, right? Just don't know how to do that. Where were you thinking I'd bolt the piece of rubber (see attached photo). Why not just use a ...softer spring? Just scared about this because, if I throw my BRAND NEW belt, it will stretch and become closer to junk. I've bought probably 3 or 4 belts in the last few months... :-(

I wonder if I ...leaned on the idler arm and try to bend it up a little?