Mower Belts, Pulleys, and Deck

[TylerFrankel1]

Hey everyone! I mentioned this in a post a while ago, but it was off topic for the post's original purpose, so I figured I'd make a new post about it.

I have a Troy-Bilt Bronco Lawn Tractor that I got free of the street for trash. It just had valves out of adjustment. I fixed that, now the engine runs like a dream. 18.5 Intek. I also replaced the sump gasket, oil and filter, battery, air filter, and blades. New fuel filter is coming. The air fins are clear well. Had to replace the starter gear because somehow the C clip got off and I never found it, or the spring/gear/washer on top. But it runs well now. Very smooth. Loud, because there's a rusted out hole in the muffler.

Anyway It had all the drive belts on it when I got it. The front/main belt was the most cracked belt I've ever seen. It ran for a good bit of time like that, however, probably an hours worth of time. I knew it would shred and it did. So I bought a new one and replaced it. The rear one looked acceptable, although I have doubts now.

After replacement, the mower works pretty well, but I feel like I'm getting some slipping. After long use one day, I lost nearly all forward power until I let the mower cool. Sometimes when it first starts up it has low movement power too. And, it has never felt particularly quick. My GPS speedometer from my phone measures 3-4 MPH when it should be more like 5, although I doubt the accuracy of the GPS. So I went and inspected the rear drive set-up and recorded what I found. Here's that video:

I found the variator pulley is slightly loose. I think that's my fault, because when I replaced the front belt I had it off and I may have overtightened and consequently stripped the bolts. To solve this I plan on drilling a third bolt hole and using a nut on the other side to actually get it locked in place (which is how Troy-Bilt/MTD should have done that in the first place).

I found that the transaxle pulley is not perfectly round. This makes no sense.

I found a slight groove in the variator pulley. Not severe but present

The middle plate in the variator moves freely

The idler pulley is noisy but spins just fine.

The belt in the back has minor cracks and may be glazed. I don't have a ton of knowledge here so I don't know if the belt is bad enough to cause these problems. I don't care if it's on the brink of failure, I'll run it until it dies, but if it's causing the slipping or power loss I'll replace it.

I didn't check the 2 idler pulleys underneath yet but if memory serves me correctly they spun freely if slightly noisy.

I found that the stupid belt won't come off the transaxle pulley unless the pulley is removed because there isn't enough clearance between the fender and the pulley.

The single little bolt that goes between the belt in the middle of the mower is in place.

So I don't know what the issue is. I'd guess it's a worn belt and the loose variator

Also, a different issue I've noticed is with the deck. It sways around a bit when the PTO is engaged. Nothing violent but noticeable. The Spindles are sealed so I can't really grease em. I would assume worn spindles are at fault, but they kick in/engage really quickly and smoothly and the mowing sounds/looks normal. I wonder if it may be because of my handy-work on the deck. It was rusted through, and I just bolted some sheet metal underneath where the holes were. The structural metal was fine btw. Perhaps the aerodynamics are affected by this and causing the swaying. If it's the spindles then unless it's gonna kill somebody I'll let it be and run the spindles till they die. I have a spare deck with spindles that may be good anyway.

 

[TylerFrankel1]

Was wondering if anyone has advice about noisy pulleys. I've heard that they should be dead silent. I personally don't see the harm in them being noisy as long as they spin freely. Sure, they probably are approaching the end of their life, but as long as they're checked frequently to ensure they spin freely what harm could it cause? I look at it the way Taryl Dactal does: It ain't the space shuttle, it's a lawn mower.

 

[bertsmobile1]

A noisy pulley has no grease in it
The end result is the same as running the engine with no oil.
Even worse they can take the belts with them.
So yes the top pulley has to come off because the side of the engine acts as a belt keeper.

They system works as a tug 0 war between the two belts .
Engine belt wins then go quicker.
Top belt wins you go slower
These belts should always be replaced as a set .
And I mean a set .
So 2 genuine MTD belts or two OEM aftermarket belts from Stens, Rotary, PIX or Oregon .
They are not standard profile or lengths so NAPA is out of the question .

And a loose variator will play havock with the tug o war.

BE careful tightening the nut on the big pulley the shafts are prone to stripping the splines .

 

[TylerFrankel1]

A noisy pulley has no grease in it
The end result is the same as running the engine with no oil.
Even worse they can take the belts with them.
So yes the top pulley has to come off because the side of the engine acts as a belt keeper.

They system works as a tug 0 war between the two belts .
Engine belt wins then go quicker.
Top belt wins you go slower
These belts should always be replaced as a set .
And I mean a set .
So 2 genuine MTD belts or two OEM aftermarket belts from Stens, Rotary, PIX or Oregon .
They are not standard profile or lengths so NAPA is out of the question .

And a loose variator will play havock with the tug o war.

BE careful tightening the nut on the big pulley the shafts are prone to stripping the splines .

I was afraid that the loose variator was at fault. Ill try tightening it. I know they do the tug of war thing, it kinda reminds me of a cvt system. Pretty cool, pretty unreliable. I’ll go get a new belt and fix the variator to see if that helps. I’ll also be careful with that bolt. Think 8 foot pounds is safe? 10?

As far as pullies, I’ll see if I can re pack them with grease or buy new ones. Apparently to replace the two under the deck one of them requires a hole drilled up top to access a nut and I really don’t feel like replacing that. I think that I’ll replace the easy two or see if I can re pack the grease, and spray the other with WD-40 at every use. I’ll just keep checking them.

 

[bertsmobile1]

You can get to the heads from underneath to replace the idler pulleys .
You can inject grease into the bearings with a syringe to extend their life a bit but the price of them makes faffing around a bit of a waste unless you are really strapped for cash .
Never put WD 40 or similar anywhere near a sealed bearing.
It will get past the dust seal then dilute the grease even fasted and the bearing will fail sooner.
Both of the under deck tensioning pulleys should be on the same plate so at a pinch you can unclip the accelerator link & drop the arm.
With my customers I replace the pulleys as a matter of corse.
Pulleys are about $ 20 a hit Lower belt is $95 & upper is $ 70 so wrecking the belts to save $ 40 on pulleys is a no brainer .( these are $ Aus )

 

[TylerFrankel1]

You can get to the heads from underneath to replace the idler pulleys .
You can inject grease into the bearings with a syringe to extend their life a bit but the price of them makes faffing around a bit of a waste unless you are really strapped for cash .
Never put WD 40 or similar anywhere near a sealed bearing.
It will get past the dust seal then dilute the grease even fasted and the bearing will fail sooner.
Both of the under deck tensioning pulleys should be on the same plate so at a pinch you can unclip the accelerator link & drop the arm.
With my customers I replace the pulleys as a matter of corse.
Pulleys are about $ 20 a hit Lower belt is $95 & upper is $ 70 so wrecking the belts to save $ 40 on pulleys is a no brainer .( these are $ Aus )

Good to know about WD-40. I hope you're right about the pulleys from underneath. I watched a video where Taryl Fixes All replaced them on the same style mower I had and he said you had to drill it because there was a nut up there that isn't welded so it'll just spin around when you try and unscrew the bolt. Maybe I can just take off the arm.

 

[bertsmobile1]

The thing to keep in your head is "they had to make this some how" .So if a factory worker made it you should be able to pull it apart.
It is times like this that I notice the difference between a quality mower and one built down to a price .
People here poo poo me when I advise others to buy the "overpriced JD's " where those nuts / bolts are not only captive but generally all the same size .

I am yet to find one where the parts that need regular replacing like pulleys can not be removed from under the mower.
Even the ones with non captive fittings .
Some have been a real PIA where you need to modify a spannar , but that is what cheap tools are made for .

No one here ca n be more specific without better information from you.
There were a lot of changes to the Bronco as they cut costs every season so we really need the full model & serial numbers from the tag under the seat to bring down the correct IPL .

 

[TylerFrankel1]

The thing to keep in your head is "they had to make this some how" .So if a factory worker made it you should be able to pull it apart.
It is times like this that I notice the difference between a quality mower and one built down to a price .
People here poo poo me when I advise others to buy the "overpriced JD's " where those nuts / bolts are not only captive but generally all the same size .

I am yet to find one where the parts that need regular replacing like pulleys can not be removed from under the mower.
Even the ones with non captive fittings .
Some have been a real PIA where you need to modify a spannar , but that is what cheap tools are made for .

No one here ca n be more specific without better information from you.
There were a lot of changes to the Bronco as they cut costs every season so we really need the full model & serial numbers from the tag under the seat to bring down the correct IPL .

I get what you mean. I did have to drill through the top, and sure enough, I found the nut there. Not welded to the frame of course. That would be too easy. I would have bought a nicer lawn tractor for myself if I had money (or even an intent/need to get one), but this was just a trash pick. I cut grass for some neighbors, and the local pool, and I figured it'd be nice to have when I saw it out for the trash, and since I love fixing old junk, I couldn't help it. It has been nice to cut with so far and cut my job times in half. Only issue is that I spend the time saved fixing it!

The model is 13aj609g766
The engine is 31p777-0293-e2

 

[TylerFrankel1]

Well I went around and took the rest of the idlers off. They all spin pretty well but I can tell there's no good lubrication left in em. I'll replace them. I got off the variator pulley which I'm going to add a bolt to so it stops working loose. I got the old belt out and the trans pulley off. Everything's gonna get replaced or maintenance now. I'm kinda concerned now though, because I used this opportunity with the trans pulley off to clean around the casing and noticed that it's caked with dirt, the kind of dirt that accumulates around grease/oil. There was a spot in the casing where I could wipe off grease with my finger. So it's clearly leaking. Thing is, this is a sealed unit and I can't get the wheels off of this thing either because of how seized they are, so dropping the transaxle will be hard. I've been considering trying to use a car jack to force the wheels off by putting it in sideways between the frame and rim. I also looked at the deck again. Somehow the blades loosened themselves AGAIN. I took my torque wrench and put them at 80 foot pounds. That had better hold. I also think the spindles are wearing out because there's a bit of play in them and you can hear them spin. But of course, bearings are sealed, no zirk. And the deck still shakes a bit when PTO on. Could be the deck belt which is worn, or the spindles. I think that I'll just run the spindles and belt until they fail unless there's an easy fix for em. The transaxle though I do want to deal with before it breaks, they're more expensive than this tractor is worth.

 

[TylerFrankel1]

It also makes a bit of audible noise when pushing in neautral. Not a squeaking but like a grumble. Not grindey, but like you can hear parts meshing.

Edit: The noise may have to do with the brake dragging but I don't think so.