Up graded the sheave

Maybe this might be a little help for all to understand just what is happening. This is Todd, Of Hunterworks, research.
Hope it helps!



Default Prowler Machined Sheave Update
For those who don't know what a sheave is let alone a machined sheave, here is the explanation:

The primary sheave is what we are talking about and it is the pulley in the CVT transmission that is attached to the engine. The secondary sheave is the one attached to the transmission.

A machined sheave is where we take the primary sheave and machine out the ends of the slots where the roller weights ride so they can ride out further in the sheave which pushes the belt in more which makes the belt ride higher in the sheave thus decreasing the "gear ratio" of the transmission which in turn makes the vehicle go faster with lower RPM, kind of like overdrive if you will.

After I got thru with all the engine mods on the Prowler I started testing a machined sheave on the Prowler. We didn't know where to start as far as how much to machine out so we took a stab at it, we stabbed wrong. The first one allowed too much of the belt to ride out of the drive pulley but boy was it fast, 75mph on the dyno and 61mph on the road. We took another sheave and got it right, the belt rides safely in the drive sheave and the top end was not hurt but by 1mph. We also went a step further by smoothing the transition in the roller weight slot in the sheave so the roller weight does not just flop over a machined lip in the slope, we beveled the edge so it rolls smoothly.

The problem I found on the Prowler after installing all our performance mods and the machined sheave was my top speed was only 55mph and mid-range performance was suffering. I had the same issue with the Rhino after I installed performance mods to it too. What I think is happening is with the increased torque the roller weights are getting slung out too fast and basically shifting the CVT in high gear to quick. Yes I know there are no gears but what I mean is the belt is moving too quickly to the top part of the drive sheave. I have had a theory for a while that the solution was lighter roller weights in the drive sheave. I had some roller weights from a EPI clutch kit for the Prowler that were lighter so I installed them and what do you know, my top speed came back. What is happening now is the CVT is staying in "low gear" longer and allowing the engine to run in a range it likes better thus giving my speed back.

Neither the machined sheave or the lighter weights hurt bottom end performance with all the engine mods I did to the Prowler. Also I found out a clutch kit was not needed either with the engine modified. Read the article on the CVT Transmission for more info on this subject.

I will tell you that without our forthcoming CDI unit all of this is of no use as you won't be able to use any of clutch mods until we get our CDI out that will allow more RPM.

All this being said I guess I am "the last person on earth who thinks a machined sheave is a good idea" but it alone was not a good idea. Actually someone in the forum said this to me but as with most everything these days I question it and then test it myself whether it is on our dyno or road testing.

If any of you Rhino owners are reading this, we will be figuring out the Rhino machined sheave for ourselves as well and if it works out we will be selling machined sheaves for the Rhino with whatever is needed as well.

Some of this is not news to the more techinically savvy reader but I had to see for myself and the lighter weight theory has also been thought about by someone else as I have seen a machined sheave for a rhino for sale with roller weights included with it too.

Here's another one !!!!!!!!!!!!!!!


Hunterworks Hunterworks is offline
Hunters Dad

Join Date: Jun 2004
Location: Collinsville, MS
Posts: 4,592
Default Machined Sheaves
For those who don't know what a sheave is let alone a machined sheave, here is the explanation:

The primary sheave is what we are talking about and it is the pulley in the CVT transmission that is attached to the engine. The secondary sheave is the one attached to the transmission.

A machined sheave is where we take the primary sheave and machine out the ends of the slots where the roller weights ride so they can ride out further in the sheave which pushes the belt in more which makes the belt ride higher in the sheave thus decreasing the "gear ratio" of the transmission which in turn makes the vehicle go faster with lower RPM, kind of like overdrive if you will.

The jury is still out on for me on this one. Now one guy told me I must the last person on the planet who thinks that the machined sheave is not the way to go. I didn't say it wasn't, just I have not finished up all the testing I want to do personally before we start selling them again. This time we will have our own machined not buy them from someone else, let me tell you why.

I have used machined sheaves from two different sources and they may be the only sources right now, I have not checked lately. Anyway, I am not happy with either and let me point out why.

1. The use of the spacer they both include pushes the primary sheave out which allows the belt to ride lower in the sheave and makes the belt ride higher in the secondary sheave so high as to rub the CVT cover causing damage to the belt and the cover. NOT GOOD.

2. Machining out the bottom of the channels where the roller weights ride for more bottom end is just wrong as the weights are basically never there or just during idle. BAD SELLING POINT

3. Machining out too much of the sheave by at least one of the present suppliers has caused the belt to ride too high in the primary sheave losing grip, over heating and the belt gets destroyed. NOT GOOD

4. Machining the sheave wrong causes a step in the slot for the roller weights to ride in and makes the RPM jump up and down before it settles in. Both suppliers do this. NOT GOOD.

So how do we fix this?

1. We don't use the spacer
2. We don't machine out the bottom of the slots
3. We don't machine out as much material as the others
4. We machine a smoother transition

Ok we fix all this and start selling them, right? Nope

We have to figure out just the right amount of material to machine out and make sure we get the transition smooth.

Secondly, I feel there really needs to be a roller weight change that goes along with the machined sheave, possibly a secondary spring and nobody else is doing that. The reason I feel that is because one of my Rhino's has a machined sheave on it along with a good many of performance mods and the midrange suffered after the install of the machined sheave. The reason for this is, it is shifting into "overdrive" too soon and lowering the RPM's to get it out of its power range. What I don't know at this point is whether it is because of the higher HP making the weights sling our faster or simply the machined sheave. The weight of the roller weights control what RPM the engine runs at when the belt is at its highest position. So you take the RPM at which the stock engine runs when the belt is in its highest position, 6000 RPM and then you put the machined sheave on there now the engine runs at say 5000 RPM, it takes it out of its power band. I can't remember the RPM the engine runs at exactly with the machined sheave so 5000 might not be right. Anyway this is the same as getting in a car that has a five-speed transmission and shifting from 1st to 5th and it loses power until the engine catches up.

Some people say they don't experience what I am talking about and as of today I think it might be happening with just modified engines because the there is more torque causing the weights to sling out faster due to centrifugal force.

With the last thing being said that is why HW does not sell them yet. I want to do a good bit of testing with modified engines and unmodified engines to find the right mixture of machining and use of additional roller weights or not. This is on the back burner for now because we are currently working on Prowler performance mods.

Edited 1/5/07
Read the article Prowler machined sheave, it has the latest info on machined sheaves in it.

I hope this makes everything clear as mud or at least better. When testing is done I will add more to this article and we will start selling the machined sheaves again.
Last edited by Hunterworks : 01-06-2007 at 12:27 AM.

hummmmmm just wrong.....

"2. Machining out the bottom of the channels where the roller weights ride for more bottom end is just wrong as the weights are basically never there or just during idle. BAD SELLING POINT"

Big R, did you put a spacer between the sheaves? It separates the two sides of the sheave causing the belt to sit lower thus essentially giving you a lower gear. KMS I think used to send one with their sheaves, maybe Unleashed does as well.

Tiger Rag wrote:

Big R, did you put a spacer between the sheaves? It separates the two sides of the sheave causing the belt to sit lower thus essentially giving you a lower gear. KMS I think used to send one with their sheaves, maybe Unleashed does as well.

I thought the spacer sat on the inside of the inner sheave, between the motor and the inner sheave on the output shaft. At least that is how my shims on my King Quad worked. I have never heard of anyone putting the spacer between the two sheaves, but then again, I have never been into the CVT on the Rhino, and I am by no means an expert on Rhino clutch kits.

airborne LT
The shims on your king should be between the inner sheave and the collar that the outer sheave slides in and out on.

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Yes, you are right..........I am wrong. I was foggy since it had been so long since it was apart.

Tiger Rag wrote:

Big R, did you put a spacer between the sheaves? It separates the two sides of the sheave causing the belt to sit lower thus essentially giving you a lower gear. KMS I think used to send one with their sheaves, maybe Unleashed does as well.

No spacer just a sheave.