Here is a new flyweight especially designed for the bigger displacement, higher torque motors. For all of you swapping flyweights to make your sled faster or for changing conditions, the big twins and triples now make so much power that tuners have a hard time finding flyweights able to squeeze the belt without slipping it.

Here is the bottom line in clutching. Heavier flyweights generate more centrifugal force. If you increase the horsepower of an engine, you would normally add more weight to keep the engine pulling as hard as possible and not over and under rev. If you throw all the weight at your engine that it can possibly handle in each range (low end, mid range and top end) without the engine RPM dropping below your target shift RPM, and your sled holds this RPM all the way across the shift curve, that is the heaviest flyweight you can install regardless of who clutches it.

The problem with most flyweights is you find a heavier one that makes the sled faster off the line (generates more centrifugal force), but the engine can't pull this heavy weight all the way through the shift pattern, so the engine loses RPM and is slower up on top. On the other hand, a lighter flyweight gives the sled a "revvy" feeling and may let you hit your target shift RPM, but the sled accelerates slower because you generate less centrifugal force. Sure, we could get into experimenting with various flyweights, grinding and filling them, or trying all different kinds of curvatures, helixes, springs and the rest, but for most performance minded tuners there is a simple and easy way to make your sled go faster, without spending a ton of time or money.

Adjustable flyweights are available in several different configurations, but the new ''Heavy Hitter" from Thunder Products may be the one you need. Similar to the original Thunder Shift Kit, the "Heavy Hitter" is a full body weight that allows full contact with the roller, with no "offset" mass. The Heavy Hitters are available in two different base "weights" of 54 and 57 grams, and can be "loaded" with up to 15 more grams (plus an additional 4 grams for a total of 19 grams more with optional tungsten shims). These bushed weights provide virtually any combination between 54 and 76 grams! The amount of mass in the heel area has been increased significantly to provide more belt squeezing force at low shift ratios, with three threaded holes allowing you to add or subtract the exact amount of weight in locations that control the low end, midrange, and top end. Forget about swapping flyweights, this one set can be adjusted to near perfection.

The "low end" hole comes in from the pivot end of the weight, allowing the addition of Allen head screws to throw even more weight at the engagement and "holeshot" portion of the shift curve. This can be done without even removing the flyweights from the clutch. Adding weight to this hole has a similar affect to increasing the start angle of the helix. Two threaded holes located in the underside of the weight provide midrange (middle hole) tuning and top end tuning (tip hole). Precision fasteners (with nylock locking patches) and washers allows a tuner to set the weight at each hole with exacting precision, 0.4 gram resolution.

Tuning with the Heavy Hitters, regardless of what springs, helix, or other components you have, is very simple. To begin, configure the Heavy Hitter to a mass similar to your current flyweights. If your sled has 54 gram weights, "build" a set of 60 gram Heavy Hitters, then run the sled and watch your tachometer. Add as much weight to each hole (range) as you can and still reach and maintain the shift rpm for your sled. If right off the line the engine over revs, add more weight to the low end hole. If the RPMs are too low, subtract weight from the low end hole. Do the same for midrange and top end, watching your tach. Load each range until the RPMs drop too low, then back it off slightly and you're there.

The main attraction of the Heavy Hitters is the ability to have a single set of flyweights that can be used out East or out West, warm or cold, 120 pound rider or 400 pound heifer, before and after engine mods. These flyweights drop right into Polaris, Arctic Cat, and Comet clutches with no alterations or modifications. They're made out of billet stock and have been spin tested up to 17,000 RPMS.

We're not making the claim that Heavy Hitters alone will allow you to do everything that all other clutching options can do, but regardless of what other mods you've found to work, the TSK can likely improve upon it simply due to the ability to fine tune each range with such precision. Most every tuner knows that the set of flyweights they've found to work best could be even better. There is some area of the shift curve that could be improved upon. This could be the ticket. Heavy Hitters will soon be available from many performance shops, or can be ordered directly from Thunder Products at 320-597-2700.