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Toro Z500 74296 Deck Belt Keeps Coming Off Zero Turn While Cutting

08827

LawnSite Member
Howdy!

I thought I had this problem resolved. I keep having to purchase new deck belts for my Toro 74296 zero turn lawn mower. It has a 60" deck. I went through 3 belts this season alone. This mower has perpendicular mower drive pulley mounted on a 27HP Kohler engine. The belt goes over this pulley in the rear, then over two perpendicular pulleys also in the rear, before getting routed to the deck in the center of the mower. I took apart the rear pulleys and cleaned them, installed a new spring on the left one, and lubed them. I removed the one bushing and inspected it and it looks like new. I adjusted all of the belt guides so nothing is rubbing against the belt. I greased all of the pulleys on the mower and checked that all of them spin freely with minimum wobble. Everything seems to be in perfect order. I put a new belt on this morning and it was tight as can be! I had to really wrestle with it to get it over the idler pulley. Once installed, I mowed the lawn for about half an hour and the belt broke. It usually always breaks or falls off the same way with the belt get pulled under the idler pulley. This was an aftermarket belt 5/8" x 242" and sold to be compatible with this mower.

I should point out that I've purchased an OEM belt and it broke too. I've tried a bunch of different brands of belts, but I can't figure this one out. Also, the belt is super tight! My hand will hurt for days from twisting the belt onto that idler pulley. Once installed, the spring mounted pulley gets pulled up until it almost touches the mower's frame.

Does anyone have a clue about this? Thanks!
 

hal

LawnSite Fanatic
Location
Georgia
Is the belt wobbly when engaged? Are the blade spindles in good order? Loose? Wobbly?
 
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08827

LawnSite Member
The belt moves smoothly on the deck portion - no wobble at all. When I first engage the blades, however, the pulley in the rear of the mower (the one with the spring attached to it) moves up and down a bit until the mower is running at full speed. The blade spindles are in perfect shape! Blades are nice and sharp too! Nothing is loose. Thanks!
 

hal

LawnSite Fanatic
Location
Georgia
You have a horizontal engine, had a grasshopper the same way. Are the grooves deep enough on the pulley it hops, all the springs in good shape? Something is grabbing or not moving smooth enough cause it to jump.
 
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08827

LawnSite Member
No, the machine is like new. I baby it. It has about 400 hrs on it on my own private property. I put a new spring on this morning and the pulleys are clean and in perfect shape. It took them off and inspected each one. The only thing that looked funky was the washers used on the two bolts that the pulley spring in the rear hook onto. The hole in the washers seems large, but I can't see that causing any problem other than a minor amount of rattle.
 

Johnagain

LawnSite Senior Member
Location
Altoona, Florida
One thing to check is the bushings or bearings in the idler arms themselves. If bearings they don't move much and will start to lockup. Remove belts and check if arms move freely. Maybe even remove arms and check bearings that way.
 
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08827

LawnSite Member
I have two idler pulleys on this mower: One on the deck with no springs anywhere on the deck. The other is in the rear, which has a spring to maintain tension. This spring is brand new OEM.

I just went out to the deck again this evening and checked the pulleys on the deck. I tried wobbling them with all of my might and they would not budge at all. All three blade pulleys and deck bearings spin as quiet as can be and they are smooth. I did notice there was a little play on each of the side pulleys, with the most play in the deck idler pulley. Not much, just a VERY little. They do spin effortlessly and quietly though.
 
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08827

LawnSite Member
One thing to check is the bushings or bearings in the idler arms themselves. If bearings they don't move much and will start to lockup. Remove belts and check if arms move freely. Maybe even remove arms and check bearings that way.
The idler arm in the rear of the mower? The one that hangs down from a spring lever? As I mentioned early on, that one does shake a lot when the mower is first started. I took it apart this morning to clean it and install the new spring on the one end. I didn't think to check the bearings at that time. The Toro dealer told me several years ago it is normal for that pulley to shake, but everyone always says it looks weird.
 

Johnagain

LawnSite Senior Member
Location
Altoona, Florida
Does the idler arm on the back of the mower move freely without the spring attached? When was it greased last, any wobble? Either that or the plate that holds the one idler pulley on the deck could be the problem. Looks like you can adjust that pulley tension on that plate on the deck by adjusting the position of the pulley looking at the drawings.
 
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