By Steve Dex Charon, UTVCrap.com
Unlike traditional automatic transmissions used in cars that are much too heavy for a side x side vehicle, CVTs don’t have any sort of gears. The CVT operates on a pulley system that allows an infinite variability between highest and lowest gears with no discrete steps or shifts.
CVTs used in Yamaha Rhinos, Polaris RZRs, Kawasaki Teryx, Polaris Rangers and Arctic Cat Prowlers have three basic components:
- A rubber belt
- A variable-input “driving” pulley
- An output “driven” pulley
The variable-diameter pulleys are the key to a CVT. Each pulley is made of two cones facing each other. A belt rides in the groove between the two cones. When the two cones of the pulley are far apart, the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together, the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger.
One of the two pulleys is connected to the crankshaft of the engine. This pulley is typically called the drive pulley. The second pulley is called the driven or output pulley because the first pulley is turning it. The driven pulley transfers energy to the transfer case and onto the differentials, through the axles and out to the wheels.
On a Yamaha Rhino, the clutch sheave is part of the drive pulley. When clutch sheaves are machined, it allows the cones on the drive pulley to collapse even further which forces the belt even higher between the cones. This translates to a higher gear.
When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change relative to one another, they create an infinite number of gear ratios.
The sheave is the engine driven pulley of the belt drive. The sheave is located under the black plastic cover under the drivers side seat. It consists of 2 sides, the inner side (called the fixed half by Yamaha) and the sliding side. It is the sliding side that is modified to add additional speed to a Yamaha Rhino.
If you look at the picture below, you will see the wear marks where the belt stopped short of using the entire pulley face.
Inside the sheave are rollerways. It is centrifugal force that forces the rollers to push outward on the ramps in the rollerways, that in turn forces the sliding half of the sheave towards the inner fixed half. That in effect closes the gap in between the two pulleys forcing the belt to ride higher. By the belt riding higher in the pulley the ratio of the belt drive system- That’s why it’s really a continuously variable transmission (CVT) and not a ”clutch” at all. The term clutch kit is just a generic term used by everyone in the aftermarket industry.
In this picture you can see the inside of the sheave and the roller ways.
There are 8 rollers in a Rhino’s sheave. Depending on the machine the roller will vary in weight to change how fast the sheave will move or ”shift”.
Here they are with the outer cover and cam plate removed. That is where the rollers will rest at idle and when the sheave is fully open.
The rollers used in the 450 and 660 Rhino have removable covers. The factory roller on a 700 Rhino is one piece, our rollers for the 700 are 2 piece.
If you are simply replacing the outer sheave half to gain more mph than you do not need to separate the roller weights. If you are adding a duner/sport or big tire kit where you are changing the gram weight of the rollers you will need to separate them from the covers.
The easiest way to do that is to use a socket that just fits inside the roller cover to push the roller out.
You do need to pay attention to which way the roller comes out of the cover. There is a lip on just one side of the cover that, the roller only comes out and goes in one way.
When you are reassembling the sheave you will need to apply grease to the rollers. About a teaspoon for each roller will be enough. Applying a little to the four walls that the slider rides on will not hurt either but after the first time the sheave spins the grease will end up on the walls anyway.
The cam plate is what holds the sheave on the engines output shaft. On the 450 and 660 Rhino the cam plate buttons are each two pieces, a metal insert with a plastic outer.
The Rhino 700 model has buttons that are only plastic/nylon. These have been shown to wear out prematurely and can be replaced with the older equivalent. cam plate will look like this when the buttons are installed.
On the 450 and 660 machine the metal insert should fit like this if you put it on without the plastic housing. If it does not the cam plate is worn beyond use and needs replacement.
Using a worn cam plate can result in broken rollerway walls as the rollers will be forced to cock to the side.
This is the cam plate installed (less grease).
All Rhino sheaves will have an o-ring under the sheet metal cover. You need to leave the o-ring in place as it keeps the grease from leaving the inside of the sheave. If you damage yours while disassembling the sheave it will need to be replaced. It will go in the groove around the outside of the sheave.
The outer cover will be a tight fit over the o-ring. When the sheave is properly assembled it will look like this.
Do NOT apply grease to the shaft the sheave rides on, it will end up on the belt.
When installing the sheave it is important to hold the cam plate tightly against the sheaves hub. Otherwise one or more of the rollers may fall out of it’s pathway and the sheave will not function correctly.
UTV Crap Yamaha Rhino 660 Clutch Sheave and Clutch Kit Installation
UTV Crap sells machined Rhino clutch sheaves, clutch kits, clutch spring compressors and just about everything else for your Yamaha Rhino. Check out their Yamaha Rhino Clutch page at: http://www.utvcrap.com/index.php?cPath=26_132
About UTV Crap:
UTV Crap designs, manufactures, fabricates, packages, markets, and sells parts & products for the UTV industry for all major manufactures of UTV’s and side by sides. UTV Crap is located in Phoenix, AZ at 4244 W Dunlap Ave. UTV Crap can be reached either by visiting the website 24/7 at www.UTVCrap.com or calling the retail location at 623-934-3070, Monday-Saturday 9am – 6pm.