Most of us who own and build high-powered snowmobiles know one of the weakest links in the entire drivetrain is the primary clutch, and...

Most of us who own and build high-powered snowmobiles know one of the weakest links in the entire drivetrain is the primary clutch, and its ability to transfer the power from the engine through the CVT belt-drive system. The basic primary clutch design used in today’s CVT drive system has been around for over thirty years, and has remained relatively unchanged for the duration. When this design was introduced, being able to transfer 100 HP was about all that was required of the system.
Now days, with the likes of big-bore four strokes, turbochargers, superchargers and 1000+cc monsters that can make upwards of 200 (and even 300) HP, the power transferring capabilities of the simple CVT primary clutches has been brought up to and past their original design intent. Being able to grab the belt and keep the slippage to a minimum is critical to getting the power from the crankshaft to the ground, and to keep the drive belt from disintegrating into a cloud of black smoke. This has opened the door for many new clutching approaches and designs, including the new Rage VIII 8-arm primary clutch from Supreme Tool, Inc.
Instead of the traditional 3 cam arms, or the popular 4-cam arm designs found on many of the higher power engines using a CVT belt drive system, the Supreme Tool Rage VIII distributes the power through eight cam arms. All eight arms engage the belt at the same time, providing nearly double the amount of force to the drive belt than a four arm design. Once the movable sheave has shifted (closed) 1/2 to 3/4 of its travel, the four supplemental cam arms sign off (quit applying force) due to the centrifugal force that holds them suspended above the movable sheave rollers. This allows the four main cam arms to finish the shift and maintain the proper operating rpm.
This design allows the Rage VIII primary to grab and hold the drive belt on high-powered machines, instead of slipping the belt. The added force during the first portion of the shift curve eliminates the biggest problem that racers of the high-powered sleds have had for years – belt slipping and over revving during hard acceleration through the first portion of the shift curve! This is where the primary is also working with a smaller contact patch, due to the smaller belt diameter at the lower shift ratios.
You can now change and control the initial shift curve in two new ways. First is by adding more mass to the supplemental arms, second is by changing the diameter of the supplemental roller diameter. It’s really simple. By decreasing the roller diameter, the supplemental arms let go of the shift earlier; by increasing the roller diameter, the supplemental arms shift longer before releasing.
The Rage VIII a-arm clutch uses most any cam arms offered on the market as the main flyweights, utilizing Supreme Tool’s retrofit pin design. The four supplemental arms will be provided with the Rage VIII. They will be capable of having extra mass (weight) added, allowing you to adjust them for that killer holeshot. Three different sizes of rollers are also provided to compliment the tuning capabilities of the system.
Supreme Tool has spent many hours testing this package on their track dyno, as well as on the ice strip in the winter and out on the grass drag strip during the summer months. They are convinced that if you have the need or desire to compete, you will sooner or later discover what this system has to offer, as the Rage VIII has demonstrated its capability to squeeze and control the drive belt in high-powered clutching applications.
The Rage VIII 8-arm clutch system will be available in 8”, 8.25” and 8.5” diameters and will fit all OEM crankshaft tapers. It will be offered in a screw-on or quick-change spider design as well. To order your or to learn more contact Supreme Tool, Inc. at 248-673-8408 or visit their website at

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