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Discussion Starter · #1 ·
You'll probably notice immediately that this isn't a snowmobile weight, but after searching the internet for daysssss, it appears that the most knowledgeable flyweight conversations happen on this forum! I apologize if this isn't allowed.

The vehicle (John Deere Gator) has a jerky engagement. It snaps into engagement, and it snaps out of engagement. It didn't do it with the stock weights. (we installed diesel weights and spring so we could cruise around at low RPMs quietly)

So, what I'm wondering is... is the initial flat spot before the small hump considered a notch? (I've read in a few CVT books that it can be a dip ground into it, or a flat spot) I suspected that this was the case a few years ago when I installed these weights, so I removed them and ground the hump down some, but it didn't fix the problem. (not this one... this is a new one that I'm going to modify) Maybe I need to completely remove the hump and blend it in to the curve?

The other pic is how it hangs from the pin, in case that info is needed

weight edited.jpg 20210427_152633.jpg
 

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If the moveable portion of the clutch is a substantial distance from belt contact it will be harsh.Racer's refer to that as "Banging the clutch" Good luck
 

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Discussion Starter · #5 ·
Right. But it's not, or it would also bang with the stock weights, correct?

It even makes a "ting/click" sound when it idles down, when the primary goes back to resting position. Also moves freely in and out without the spring, so it's not hanging up on anything.
 

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Discussion Starter · #6 ·
I guess the question, still, is... does this weight act like one with a notch in it because of the flat spot. I remember vehicle owners of the machine that these weights are out of making mention of a jerky engagement over the years. It sounds as if it's so... and if so, I'd like to know how much modification of the profile curve I'd need to make to get rid of it. (the notch)
 

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The notch in weights are to get the weight to engage at a determind point. The weights need to be suitable to engine RPM.If you will not set your belt tolerance than the rest is pointless.
 

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Not sure about profile of oem JD weights, but Harmony is right. You need to set your clearance between belt and moveable sheave before you start doing anything. If clearance is too much, clutch sheave is going to move in to far for proper weight to roller angles. I like .005"-.015" on all clutches that can be adjusted for sheave clearance.
Don't know if using weight from a diesel Gator will ever get you acceptable smooth operation with a gas engine. Torque and rpm curves are completely different.
 

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Discussion Starter · #9 ·
Not sure about profile of oem JD weights, but Harmony is right. You need to set your clearance between belt and moveable sheave before you start doing anything. If clearance is too much, clutch sheave is going to move in to far for proper weight to roller angles.
Are you saying that it can be different, based on which weights I have installed at the time? That doesn't make sense to me. The machine runs perfectly with the stock weights. Doesn't do the weird snappy stuff. If I run it with no belt, the sheave smoothly moves from rest into the engagement area, then smoothly back to rest when you let off the throttle. With the diesel weights, you can watch the sheave jump over. Then snap back into the resting spot when it approaches idle again. It has to be the flat spot and the hump acting like a notch.

Don't know if using weight from a diesel Gator will ever get you acceptable smooth operation with a gas engine. Torque and rpm curves are completely different.
It runs perfect with them for our long trips, where we don't want excessive noise for hours and hours. Still has enough power for us to not complain about that aspect.
 

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Don't think it's so much of a hump as change of angles. First part of weight has a steep angle then breaks over into a shallower profile. Could be moveable sheave is contacting belt just slightly before end of steep angle then as rpm increased goes over "hump" onto shallower profilel for short duration. Opposite when coming to idle. Comes back smooth then makes huge drop.
I may have missed it because working right now, but any reason you can't match OEM profile with the heavier weight?
 

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I don't think that "hump" is big enough to make much difference. Not knowing how the rest of the clutch looks, (geometry), i.e what angle it sits at and where on the ramp the roller is at idle it's hard to give much advise.
 

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I’m guessing the spring is higher lb ratio then the gas one
No, by the looks of it those aren’t notched weights

Your issue is possible your spring

Their has to be someone out there doing aftermarket stuff for these. Contact them.
 

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Discussion Starter · #14 ·
Don't think it's so much of a hump as change of angles. First part of weight has a steep angle then breaks over into a shallower profile. Could be moveable sheave is contacting belt just slightly before end of steep angle then as rpm increased goes over "hump" onto shallower profilel for short duration. Opposite when coming to idle. Comes back smooth then makes huge drop.
I may have missed it because working right now, but any reason you can't match OEM profile with the heavier weight?
There's not really much available in the form of aftermarket support for the JD machines. The stock setup has the RPMs at a constant 4500-5000 while we are driving the machine basically anywhere, and going on multiple hour long rides, it gets annoying. You can't even hear each other talk. The heavier weights from the diesel are WAYYY better for cruising around. Knocks the RPMs down to 3000-3500. I just would like to get rid of the abrupt engagement.

I still think I want to get rid of whatever is happening at the sharp point of that hump. when you rub you finger over it, it is even MORE pronounced than it appears in the picture.
 

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Discussion Starter · #15 ·
I’m guessing the spring is higher lb ratio then the gas one
No, by the looks of it those aren’t notched weights

Your issue is possible your spring

Their has to be someone out there doing aftermarket stuff for these. Contact them.
I put the stock spring back in it, but the heavy diesel weights overpower them and has the clutch engaged at an idle sometimes. I thought about shimming it just enough to keep it from being engaged at idle, but then all I am doing is creeping back up on the abrupt engagement. :(

Nothing really in the way of aftermarket, unfortunately.
 

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Discussion Starter · #16 ·
I don't think that "hump" is big enough to make much difference. Not knowing how the rest of the clutch looks, (geometry), i.e what angle it sits at and where on the ramp the roller is at idle it's hard to give much advise.
The rollers sit right at the very beginning, at idle. and then it behaves as you'd imagine it would when crossing over that hump. Snaps into action.
 

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Yes,It's just a better way of stalling the shift .With a notched ramp the belt is unloaded when the roller comes out of the notch .This way it's not .
 

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Those weights are way to tip heavy for what you are trying to do. They aren't notched per say, but once the centrifugal force is high enough to overcome the spring pressure and initial ramp they will want to shift out hard. I would look into adjusting the secondary clutch to achieve what you want. The secondary needs to shift out to lower cruising rpm. You can do this with a softer spring at the expense of poor back shifting. Problem is tuning parts may be tough to find.

First thing I would do is start with a fresh belt, and all stock clutching. Make sure both clutches are in proper working condition and belt deflection is correct. Then you can start tuning from there.
 

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You'll probably notice immediately that this isn't a snowmobile weight, but after searching the internet for daysssss, it appears that the most knowledgeable flyweight conversations happen on this forum! I apologize if this isn't allowed.

The vehicle (John Deere Gator) has a jerky engagement. It snaps into engagement, and it snaps out of engagement. It didn't do it with the stock weights. (we installed diesel weights and spring so we could cruise around at low RPMs quietly)

So, what I'm wondering is... is the initial flat spot before the small hump considered a notch? (I've read in a few CVT books that it can be a dip ground into it, or a flat spot) I suspected that this was the case a few years ago when I installed these weights, so I removed them and ground the hump down some, but it didn't fix the problem. (not this one... this is a new one that I'm going to modify) Maybe I need to completely remove the hump and blend it in to the curve?

The other pic is how it hangs from the pin, in case that info is needed

View attachment 2121075 View attachment 2121076
The weight appears to be sitting in the clutch at a point where the center of mass is too far inward at engagement. This causes the snap at engagement. I'd think that some reshimming of the clutch spider to reduce belt side clearance would reduce the snap.
It works fine with the stock weights. Could that become a problem just because I am using different weights?
Yes.
 

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Discussion Starter · #20 ·
Those weights are way to tip heavy for what you are trying to do. They aren't notched per say, but once the centrifugal force is high enough to overcome the spring pressure and initial ramp they will want to shift out hard.
I don't recall saying what I wanted to do?? I love the way these ways drive around (very low rpms so we can hear each other talk while riding), I just want to get rid of the snap into engagement. I guess my next question is how I should modify these to alleviate that problem... like, how much of that "hump should I grind down"? Maybe just blend the roller resting position into the profile about midway down or so?
 
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