Belt CVT Drive

[aesmith]

This is a John Deere "Gator" farm buggy, whatever the general name is for these things. The transmission isn't working quite right, a little too much of a lurch when engaging. And if you're trying to start gently like in a confined space there's a kind of hesitant grab and release.

First thing is it needs a new belt, not only is it worn but shows cracking.

So while I'm in there what should I be looking at to make sure everything else is healthy? I can't tell from online diagrams whether the initial engagement is just done by gripping the belt, or whether there's a separate clutch function between engine a driving pulley.

Existing belt viewed through exhaust port, for your entertainment ..

 

[8ob]

The cvt bit is separate to the centrifugal clutch, a lurch when engaging gear could be too higher tickover speed or a duff spring on the clutch shoes.

Bob

 

[aesmith]

The cvt bit is separate to the centrifugal clutch, a lurch when engaging gear could be too higher tickover speed or a duff spring on the clutch shoes.

Bob

Thanks, it's not really clear in diagrams that I can find for this specific machine. If I understand you correctly does this mean that the actual driving pulley, at the engine end, shouldn't turn at tickover? Only start to turn once that centrifugal clutch engages.

I haven't received the belt yet so haven't yet taken the cover off to see first hand.

 

[8ob]

Thanks, it's not really clear in diagrams that I can find for this specific machine. If I understand you correctly does this mean that the actual driving pulley, at the engine end, shouldn't turn at tickover? Only start to turn once that centrifugal clutch engages.

I haven't received the belt yet so haven't yet taken the cover off to see first hand.

It depends on how your machine is laid out but all centrifugal clutches work on the same principle, take a squint at the typical clutch below, it takes the weight of the shoes overcoming the springs to get the clutch to engage, a high tickover or broken/weak springs will allow the clutch to engage at lower rpms causing drag. Only other possible but highly unlikely culprit can be a partially seized pilot bearing.

Bob

 

[dieselsamurai]

Sorry @8ob I have to disagree on this all the argocats and other small atvs have a variator which when the engine is idling still spins as the revs increase a weights are thrown out but they push the pulley inwards ramping the belt up the drive pulley initially its small in diameter being low gear then as the load against the driven pulleys spring decreases its spreads more allowing the driven pully to move inwards and the belt towards the outer edge giving you a higher gear but should the load increase again it will drop down the driven pully lowering the gear ratio again.

Not 100% on a gator but there is definately no brake shoes in any CVT atv ive had it doesnt need them

when idling the belt is narrower than the the two driven pulleys so just slips on the shaft

 

[dieselsamurai]

usually the ribbed part of the belt is on the inside not the outside as it looks like in your picture , is someone has fitted the wrong belt it will cause all sorts of issues

 

[finyuk2005]

usually the ribbed part of the belt is on the inside not the outside as it looks like in your picture , is someone has fitted the wrong belt it will cause all sorts of issues

you do get belts that are toothed on both sides,
What do the pulley sheaths look like? any wear there?

 

[Seadog]

Why is the belt toothed, is it to enable the variations in bend radius?
Google says the teeth are on the inside, but it does show a belt that have teeth on both surfaces

Besides, the Vee-profile controls which way it's fitted.

 

[dieselsamurai]

have to say ive never seen a double ribbed belt like that, learn something new everyday and forget something too!

 

[finyuk2005]

its not something to do with cooling is it? maybe a solid belt wouldnt cool as well, air is blown through the housing so it must get warm

 

[aesmith]

Thanks. Nothing much I can do till I get the belt which should be in the next couple of days. I've ordered genuine John Deere, from the retailer photo it's ribbed both sides ..

 

[GaryS65]

Why is the belt toothed, is it to enable the variations in bend radius?
Google says the teeth are on the inside, but it does show a belt that have teeth on both surfaces
View attachment 536750
Besides, the Vee-profile controls which way it's fitted.

Yes for tight radius on the cvt pulley.