Expecting too much from my frontmount mower?

[Buxus]

I have a new to me Grasshopper 930D with 72 inch deck. Only 275 hours. I mow fescue. It ran fine until the end of last season when I tried to grind up some already bush hogged tall grass. I burnt the PTO belts in the back when I got into some heavy stuff. Fortunately it was the end of the season.

In the off-season I had the dealer replace the belts (a fairly complex affair, unfortunately), and he said he changed the bearings also. I used it this April and promptly burnt the belts again. I was mowing what seemed like reasonable-height grass (?7 inches) to 3.5 inches. The dealer replaced the belts for free, but felt "I must have gotten into something thick, or hit something." I know the area well and doubt I hit anything.

I mowed a few more times early this month and it worked fine, but every once in a while I thought I might have heard a squeak from back by the belts. I always mow at 5.5 inches except the one time at the beginning of this season. The belts were warm, but not hot, and no belt dust. I have three zones that I mow and I mow a different one every 3 days.

Today I mowed an area that had been last mowed 9-10d ago. Grass height pre-mow was 10 inches, but not thick, just scraggly at top. Sure enough burnt a belt in back and it snapped.

My questions are:
1. Even with quick growing spring grass, is it typical that a zero turn cannot handle every 10d mowing?
2. Might there be some increased tension distal to the PTO clutch that is causing increased resistance?
3. There is a snowblower attachment that goes on the tractor portion of this unit. I am surprised it can throw snow and not mow 10d growth. Perhaps I should not be?
4. I have a tractor and a 6 ft rotary mower, but use it mainly for the fields, and do the work around the house with zero turn because it's so maneuverable. Is there a better option for around the house, gardens, etc? The Kubota F series is pricey but might be the best option. I assume it also has a belt driven PTO?

I'm awfully frustrated that it appears a 30 HP diesel is so limited by a belt.

 

[boggen]

belt types can be a large difference.

it has been awhile since i hunted for type of belt. i want to say the more expensive usually "kevlar" belts. can with stand a higher temperature, and less stretching.

i know i went through a couple cheap belts initially, till i started hunting for the specifications of the belts.

i tend to mow without the "guards" over the belts. so i can physically see the pulley above the blades. ((dangerous)) get a foot, shoe lace, etc... caught and you are done for. but only way i can keep an eye on things to make sure there is nothing clogging up and stopping a blade. generally do not pay attention to center blade (3 blades total) due to belt wraps around that pulley 2 to 3 times.

i refuse to use any sort of "belt gripper" or "belt cleaner" (other words snake oils), and make extra care i do not get any oil or grease on the belts either. any of them can cause a belt to slip and/or heat up very quickly and come apart, at least that is my experience.

you may need to take half passes (half the deck width) to mow, and slow your speed down. if you can physically see pulleys stopping, you are overloading the belt setup. and/or possibly mow all the way up / high, to cut it down, then mow over the stuff a second time.

also double check if there any weird "twists" the belt may need when it is on. it can be a bit easy to place twists in wrong spot. causing belt to twist more than it normally would and cause additional heating up.

 

[Buxus]

Thanks for the advice. The belt that keeps burning is the belt behind me that drives the PTO, not the one out front that drives the blades.

I go very slow in the thicker grass, just crawling along, but perhaps 1/2 passes and very slow would be better.

Since I posted, I looked up the Kubota F series and the PTO is not belt driven. But does this just mean the belts further down the line (i.e. the ones on the deck) burn up instead of the non-existent PTO belt?

All this is especially frustrating given that my little JD D100 that I bought for $500 mows right through the same grass with no problem. And it's max height is 4.5 inches, not 5.5 inches!

 

[IXLR8]

How sharp are the blades? That 72" deck is handling a lot of grass, but I am surprised you are burning up belts. I'm in Maine mowing mostly Kentucky Blue Grass and Fescue, as wet as it has been, I am having to mow every 4-5 days, I don't think I could go 10 days between mowings. I am surprised the D100 can handle the grass and the 930D can't.

 

[Deere Dude]

How does the engine sound when in heavier grass and you go through belts? Does it really bog down or does it not slow down much? Dothe grass clippings leave the blade area or does it just build up and bog the blades down?

In extreme circumstances I have gone through 5' tall weeds and grass with a 25 HP lawn tractor taking smaller chunks at a time, trying to make sure there is not much build up staying under the deck and go over it a couple times. Maybe don't let the grass get quite as tall as previously done because it does seem like taller grass cuts much harder. If the 100 can cut it I can't believe you don't have another problem with your grasshopper. Maybe a tensioning pulley is loose?

I can't believe that mower can't handle that lawn with one pass like a charm.

 

[aczlan]

I would bet on one of the idler pulleys being loose or cutting the belt or something like that. Do you have a picture of one of the failed belts? Would be interesting to see what the wear and breakage pattern is on it.

Aaron Z

 

[Buxus]

Thanks for the responses. I'll post a picture of the belt tomorrow. I was thinking, (and hoping) that it's an idler pulley. I feel like I have a powerful, maneuverable machine that I have to use gingerly for fear the grass is too long...

 

[Buxus]

How does the engine sound when in heavier grass and you go through belts? Does it really bog down or does it not slow down much? Dothe grass clippings leave the blade area or does it just build up and bog the blades down?

In extreme circumstances I have gone through 5' tall weeds and grass with a 25 HP lawn tractor taking smaller chunks at a time, trying to make sure there is not much build up staying under the deck and go over it a couple times. Maybe don't let the grass get quite as tall as previously done because it does seem like taller grass cuts much harder. If the 100 can cut it I can't believe you don't have another problem with your grasshopper. Maybe a tensioning pulley is loose?

I can't believe that mower can't handle that lawn with one pass like a charm.

In the heavy grass, the engine doesn't even slow a bit. It goes right through it with no problem (I am going at a slow speed) and there is no problem with how the deck throws the grass. The cut is immaculate.

Maybe the problem is that the engine is too powerful? It doesn't seem like the blades bog down at all, but perhaps they do and the engine with all it's torque just rips right through.

Does anyone ever mow at less than full throttle on the PTO?

 

[Sawyer Rob]

I have GH's 721D and a 725D, I've NEVER heard a squeak of any kind when mowing ANY grass from those back belts.

You have a problem of some kind, things to check are, bad idler, not enough tension, wrong belts, worn pulleys, misaligned pulleys...

IF I drive into too tall tough grass with my GH's, it will slow the motor a bit and then the mower deck just skips, it does NOT slip the back belts at all.

SR

 

[xring100]

Thanks for the advice. The belt that keeps burning is the belt behind me that drives the PTO, not the one out front that drives the blades.

I go very slow in the thicker grass, just crawling along, but perhaps 1/2 passes and very slow would be better.

Since I posted, I looked up the Kubota F series and the PTO is not belt driven. But does this just mean the belts further down the line (i.e. the ones on the deck) burn up instead of the non-existent PTO belt?

All this is especially frustrating given that my little JD D100 that I bought for $500 mows right through the same grass with no problem. And it's max height is 4.5 inches, not 5.5 inches!

I agree with Aaron something might be put of alignment or bad bearing. My neighbor has a 25 or 26 hp grasshopper and mows deep field grass all the time i dont believe he burns belts. If the f kubota is lile the zd it has a double v belt that powers the outer spindles. The belt is about an inch tall.

 

[4570Man]

My F series kubota eats anything it can push over. The double v belt on the deck holds back more than the 25 hp diesel can dish out. If I manage to get one blade in a bind it'll slip for a few seconds before stalling the engine. If I overload all the blades ( like mowing dirt ) it'll stall with slipping. I do run out of power trying to use this thing like a bus hog, but the cut quality suffers first.

 

[Buxus]

Thanks for the additional responses. That is what I thought. I had a 1999 720k that could mow 10 inch field grass without burning belts. It bogged a bit now and then, but never burned a belt. This spring when I brought the 930D in for the second set of burned belts I told the dealer I had not been in heavy grass and that I thought something else might be going on. He said he looked it over and everything was fine. The opinions and real world experience of TBN members gives me more evidence that something is awry. Hopefully the dealer listens and figures it out.

 

[ProjectKing]

Sounds like a loose idler pulley or improper routing of belt which causes it to rub on something. The engine should stall out before slipping a belt. Especially on a mower of that price range!

I run a Kubota ZD326 and it will mow anything you can drive it over. Never slips the deck belt. Rest of the driveline is shaft. However your belt system should not slip!

 

[aczlan]

Sounds like a loose idler pulley or improper routing of belt which causes it to rub on something. The engine should stall out before slipping a belt. Especially on a mower of that price range!

Or the pulley at o e end or the other is bent or damaged. That's why I asked about pictures of the bad belt...

Aaron Z

 

[Buxus]

Here are pictures of the broken belt and the belt that is still on that runs in parallel with the broken one. The remaining one is so stretched it's useless. I appreciate all the feedback and suggestions. I have sent at email to the GH and plan to call the dealer tomorrow.

 

[ProjectKing]

Here are pictures of the broken belt and the belt that is still on that runs in parallel with the broken one. The remaining one is so stretched it's useless. I appreciate all the feedback and suggestions. I have sent at email to the GH and plan to call the dealer tomorrow.View attachment 510148View attachment 510149View attachment 510150View attachment 510151View attachment 510152View attachment 510148View attachment 510149View attachment 510150View attachment 510151View attachment 510152

Wow! That belt is seriously worn in one spot. I wonder if there is some sort of resistance that is making the mower hard to turn?

When you engage the mower deck do you do it at idle or wide open?

It would be good to have a pic of the top pulley where the belt goes. Can't see it in the pics

 

[ProjectKing]

So a couple things to check.

1. Make sure belts are correct length. It's possible belts that have been installed are too long. This will not allow idler pulley to fully tension belts because spring is not extended enough.

2. Make sure idler pulley mechanism is properly assembled and that spring is attached to it. In your pic the spring is barely stretched. This maybe because the belt is stretched as you say... or because spring is in wrong mounting holes, etc. Or belts are too long.

Here's a pic of PTO drivetrain.

 

[IXLR8]

To me, the belt looks like it is sitting very low in the idler pulley, like it is the wrong width. Have you got a 1/2" wide belt where you should have a 3/4" wide belt?

 

[ProjectKing]

To me, the belt looks like it is sitting very low in the idler pulley, like it is the wrong width. Have you got a 1/2" wide belt where you should have a 3/4" wide belt?

Thats great observation. It does look really low.

 

[aczlan]

To me, the belt looks like it is sitting very low in the idler pulley, like it is the wrong width. Have you got a 1/2" wide belt where you should have a 3/4" wide belt?

Or a 5/8" wide belt, that is the size that the eXmark and Huskvarna mowers (60-72" cut) I used to work on used.
Also, it's the size that our current 84" rear finish mower uses.

Aaron Z