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Discussion Starter #1
Hi guys,

Great forum and first post here! I have a circa 1987 Toro 521 two-stage snowblower with a 5hp Tecumseh engine. I'm having a pretty bad belt slip problem - auger spins fine without load, but completely stops spinning when even a little snow is put in. Shear bolts are in tact - I pulled the belt cover and saw belt wasn't even moving under load.

I pulled the belt out and what has me scratching my head is that the belt still looks really good - no bad threads sticking out and teeth are in tact. The belt is a few years old, but the machine hasn't been used much since replacement. Do these belts go bad/stretch out even when they look practically brand new? Is there any way to isolate whether its the belt or a bad tensioner? Any help is appreciated, thanks!
 

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Welcome to the snowblower forum!!

A belt will streach its most when new. Could it maybe have been too long to start with? Has it ever worked well with the new belt???
 

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- I pulled the belt cover and saw belt wasn't even moving under load.

no bad threads sticking out and teeth are in tact.
Not familiar with your particular unit, but are you saying the belt has teeth that mesh with corresponding teeth on the pulley?

If this is the case and the belt is not turning, and is not damaged, I would look for the drive pulley turning on the shaft under load, unless you can see that the belt is so loose it doesn’t contact either pulley.


Geared pulleys and belts are very tough and when they do slip the belt gets destroyed pretty fast. You say your belt is good so I suspect the pulley is turning on the shaft.
 

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Not familiar with your particular unit, but are you saying the belt has teeth that mesh with corresponding teeth on the pulley?

If this is the case and the belt is not turning, and is not damaged, I would look for the drive pulley turning on the shaft under load, unless you can see that the belt is so loose it doesn’t contact either pulley.


Geared pulleys and belts are very tough and when they do slip the belt gets destroyed pretty fast. You say your belt is good so I suspect the pulley is turning on the shaft.
Hmm...very interesting point. Remind me again, which one is the drive pulley? The small upper one connected to the engine, or the large lower one connected to the auger assembly?

The belt is definitely coming in contact with the pulley, since the auger does spin when its not under load - so I don't think its an overly loose belt.

I'll have to take a closer look at the pulleys to see if they are slipping on the shaft. I just pulled the belt, but didn't think to check the condition/functionality of the actual pulley. I've mainly worked with ribbed automotive belts, so haven't seen many of these geared belts.

Thanks to both of you for your help!
 

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Drive pulley is on the engine. Driven pulley is on the auger drive shaft. At least that is the way my Ariens is. As I said I am not at all familiar with your unit. However if the auger turns when under power, but stops turning when a load is applied, then something is slipping and you should be able to see it.

Are your sheer pins intact?
 

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Drive pulley is on the engine. Driven pulley is on the auger drive shaft. At least that is the way my Ariens is. As I said I am not at all familiar with your unit. However if the auger turns when under power, but stops turning when a load is applied, then something is slipping and you should be able to see it.

Are your sheer pins intact?
Yes, the sheer pins are intact - auger blades don't move freely when I turn them by hand. If the drive pulley is turning on the shaft, what is the recommended fix - a new pulley or can I simply replace the bearing? I'm at work currently so can't look at it, but will check it out first thing when I get home tonight.

Thanks again!
 

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If the drive pulley is turning on the shaft, what is the recommended fix - a new pulley or can I simply replace the bearing?
Thanks again!
Some pulleys I have seen use a set screw, some have a roll pin. There should not be any bearings associated with the auger drive pulleys, with the possible exception of the tentioner pulley. The drive pulleys need to be solid mounted to the shafts they turn or are turned by.

As I said I am not at all familiar with your model machine. I have been making general suggestions based on my understanding of how my Ariens works. You will just have to work your way down the drive system until you find the problem. If the belts aren’t slipping on the pulleys, and the pulleys aren’t slipping on the shafts, then the next place to look is the auger gearbox, and then the sheer pins. That’s about all there is to it unless your machine is significantly different than the Ariens.
 

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Check if there is a woodriff key sheared and also if there is some allen screws that need tightening on the pulley
 

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The drive pulley (the 1 that is on the auger) has a woodrift key and a set screw. Chances are the woodrift key is broken. To replace the key, you will have to remove the bucket from the tractor to remove the pulley. Yep, it is a lot of work for a 75 cent part.
 

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Discussion Starter #12
Hey guys, ok so I've uncovered the problem - its actually not the drive pulley slipping, that is on solidly on the driveshaft. The problem is that the belt tension is waaaay too loose - I mean barely any tension whatsoever.

What has me stumped is that the belt does not appear stretched at all - I measured it and its almost exactly 29.5", the length of the standard belt according to the manual. So, the belt appears is the right length and in good condition, the drive pulley is working as it should....so the only other problem I could see is that the auger assembly and pulley is somehow positioned "too close" to the drive pulley - if I could "pull" the auger pulley further away from the drive pulley, this would lengthen the distance btw the two pullies and increase the tension.

Does this make sense and can this be done?
 

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Discussion Starter #14
Your problem is the idler pulley is not tensioning the belt. when you press the engagement lever, the idler pulley should tighten up the belts. Idler pulley is item #1 in "engine assembly" diagram.

https://lookup3.toro.com/partdex/back2lst.cfm?xCaller=Toro&o=2&x=2833
Thanks indypower. The idler pulley is tensioning though and the belt is still loose. Even when I manually move the idler pulley as far in as possible to "engage" the auger, there is still about 1-inch of travel in the belt. Without it engaged, there is closer to 2-3 inches of travel.

Can a belt really stretch out an inch over time?
 

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If everything is assembled right and all tight and the idler pulley is working then post a picture and then we can solve this real fast.
 

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Yep, a picture, if you can post one, might be worth a thousand words.
 

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A new belt will solve your problem. Even tho the belt measures the correct length, it is worn. Belts don't stretch even tho that is the term used. The sides of the belt are the important part as that is what is in contact with the pullies. The sides wear and slide further down in the pulley, thus making it appear to have stretched. If the belt is more than 3 years old, it needs replacing. And the best belt to buy is the original Toro belt.
 

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Discussion Starter #19
Ok guys - just took some pictures here. The first 2 are of the belt - as mentioned earlier, it looks ok and the teeth are intact, outside edges don't appear frayed. Just to note, none of the pulleys actually have teeth that correspond with the teeth on the belt - maybe the belt teeth are just to add traction.

The 2nd two pictures are of the belt installed - as you can see, even with the auger lever/tension pulley engaged, there is still a lot of play on the belt. I read the side of the belt and it is the same belt Toro specifies to use.

Thanks guys!
 

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Seems we chased this one all the way around the barn and ended up where we started.

I would get a new belt. Make sure it is the belt recommended by the manufacture. If you are confident you can get the correct belt from a cheaper discount store go for it. If not it may cost a bit more going to the dealer but it could prevent getting the wrong one and having more problems.

I did have a hard time with the geared pulley thing, but then I never worked on a Toro. Guess they could have used supercharger belts and pulleys on their 8000 HP models. :D
 
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