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Hi Guys,

I just picked up an old (1987 I believe) John Deere 36" walk behind. I've been restoring it and pretty much have it going except for one issue: the tensioner for the drive belt (motor shaft to transmission) has no effect at all. It's like the belt never slips and so the mower is stuck at maximum speed. I don't have a sulky so I find myself having to jog behind the thing.

See the picture of the underside of the mower. The belt that is on there is quite loose, so loose that I'd expect it to slip and thus reduce the ground speed, but it doesn't. Is it possible this belt should not have teeth and someone put the wrong belt on there?

If it helps, I think back in 87 these mowers were built by Bunton?? so it's possible they share the same parts, etc.

Appreciate any help!

The pulley contraption on the engine shaft is a variable speed setup, which when working normally, when extra tension is put on the belt, the slower the mower will go. But if the variable speed pulley is locked/rusted up, you are stuck with that ground speed.

I would try a different belt (conventional), the one that's in your photo (cogged) do not slip very well, when you pull the cable the more you pull it the faster the mover goes, ie it slips when going slower.

EngineMan said:

I would try a different belt (conventional), the one that's in your photo (cogged) do not slip very well, when you pull the cable the more you pull it the faster the mover goes, ie it slips when going slower.

Click to expand...

Naw, it don't work that way..

the pulley on the engine shaft has a big spring on it, and if you increase the tension on the belt, the pulley sheaves on the
engine shaft spread out and change the ratios like a 10 speed bicycle, the drive pulley diameter gets smaller, and the driven pulley stays the same though, but that is how the variable speed works on this model.

Looks to me like the spring that should be on the pulley on the right in the pic is gone and someone added a couple spacers.
But I could just be seeing it wrong

(( cowboy up and get over it ))

Actually, the belt should be on the other side of the pulley on the left!

Wow, thanks for the quick help guys.

Ok, so at least I understand how it's supposed to work now.

First, I moved the belt to the correct side of the tensioner. It's still too fast, so I'm assuming that the variable speed pulley is locked up and not sliding when tension is added. What's the best procedure to deal with this? Should I take it off, soak it and see if I can get it moving again? Or perhaps I can just get a smaller normal pulley somewhere to replace it? I'd be fine if it was only 1-speed as long as that one speed was the correct one! It looks like finding a stock replacement may be impossible or way too expensive.

thanks!!!

I have a problem that may be similar. I have an older JD Commercial 48 inch walk behind that I purchased off of craigslist two years ago. The first season and a half it was a beast, towards the end of last year, it started having issues going up hills and requires me to push. Pushing that big ol thing is a chore and it is getting worse. I have a couple of acres in the backyard and it has a pretty good drop. I looked under the back-end and the one smaller belt is really loose. How do I tighten it, or do I just replace it? Also the belt on the left side constantly comes off, can it be tightened, or do I need to replace it as well.

Thanks in advance for your support.

Scott