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Media
Coverage -
"Thunder
Shift Kit for Ski-Doo TRA"
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Snow Tech Magazine Oct/Nov 99 The concept of adjustable flyweights can be applied to the Ski-Doo TRA clutch, even though the TRA doesn't use flyweights. Instead, a roller on an arm applies force against a curvature (ramp) in the cover. Simply another way of doing the same thing. Anyway, the moveable arm can be purchased in different materials, as can the pin in the end of the arm. The pin mass is what Ski-Doo usually changes for high altitude applications. Instead of having several sets of pins, all weighing different, why not a hollow pin that's threaded so we can screw in different fasteners and shims? If this sounds kind of like a Thunder Shift Kit, it is. The TSK for Ski-Doo includes your choice of hollow pins in aluminum or steel. The aluminum pins weigh 3.7 grams each, the steel pins weigh 10.1 grams each. Into these, you can attach Allen head screws, aluminum bolts, or two different weights of steel bolts, along with brass, steel, or for you real nasty horsepower mongers, tungsten shims for even more mass. Your tuning "resolution" is down to 0.4 grams. Add to this the assortment of arms & rollers available from Ski-Doo and you can make almost any mass combo, with different distribution of that mass. What it boils down to is that the TSK allows you to run just about any pin mass you could possibly want or need for your application. The kit comes with complete instructions and Allen wrenches and a 5x4O thread tap for installation, along with the pins and assorted bolts and shims. Don't the adjustable "clickers" on the TRA allow you to do everything you need to? If it did, why would there be different ramps, pins, helixes, and the rest? Snow Tech has found that going back and forth between Minnesota and Idaho that we can do most all of our basic tuning with stock clutch components and a TSK. In Minnesota we may run 18 gram pins, in Idaho, 9 gram pins, or whatever. By slightly increasing the pin mass (similar to increased "tip" mass on a normal flyweight), you can tune the shift RPM to a finer degree. Manipulate the tip mass, tweak the clickers, and you now have more options to dial your clutching in for whatever the application. If this isn't enough, then you can get into different arms, rollers and ramps. On a bone stock '98 Mach 1, we found that by simply increasing the pin mass from stock 16.4 grams up to 17.9 grams that our track horsepower increased a healthy 3 HP across almost the entire curve. It pulls really hard off the line, loading the mighty Rotax triple, but it'll grunt and accelerate hard. Not bad for 10 minutes of work and $88.00! Order from just about every Ski-Doo speed shop on the planet, or from Thunder Products @ 320-597-2700.
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