| The flywheel performs three functions in scooters. It's a rotating mass that helps maintain a constant engine rpm, thus reducing vibration, and making it easier to pull away from a dead stop. The flywheel also has a series of radial fins which direct cooling air into a shroud and over the cylinder. This is necessary in a full-bodied motorscooter with an air-cooled engine, for obvious reasons. The third and most critical function of the flywheel in scooters is carrying the magnets, which create an electric charge as they pass over the coils on the stator plate. In a racer, only one of these coils is needed. One coil is for the ignition, but the others are for lights and battery, if equipped. But since a racer doesn't need lights, only one coil is required. And even that coil can be eliminated if an alternative source of juice is supplied for the ignition system. For short periods of time, a battery can provide the electrons needed for a spark, thus making the magnets and stator coils entirely redundant. |
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Good question. First, a lighter flywheel allows the engine to change rpms more quickly. This in turn allows for faster shifting, by shortening the time a rider waits as the engine speed matches the speed of the selected gear so they can mesh without clashing. It also means faster acceleration, both positive and negative. Also, a lighter flywheel is less likely to shear off the crank during hard acceleration or deceleration. And believe it or not, a few kilos of metal rotating at several thousand rpms is a pretty fair gyroscope. When the scooter leans to turn, that little flywheel can exert strong gyroscopic vectors which may affect the handling of the scooter, and may contribute to the aforementioned crankshaft failure. |
| Quinn refers to this modification as a "Total Loss" system, and I think I've heard it referred to as a "Dead Loss" system as well. He points out some other advantages: no worries about failed stator coils or demagnetized flywheel magnets, no ignition coil, and a guaranteed strong spark for as long as the battery remains charged. Further mass reductions can be achieved by grinding off the cooling fins as well, since many racers have removed their shrouds, anyway. With the side covers off, or with the entire body opened up or removed, airflow can provide adequate cooling. Know that old flywheel with the broken fins? You didn't throw it away, did you? Drawbacks include an increased risk of over-revving when you miss a gear. Also, you'll have to rev the engine a bit more to get the scooter rolling from a dead stop, because you'll have less rotational inertia to trade off. Plus, your spark will only last as long as your battery, so this won't be practical for an endurance race. The newly-lightened flywheel should be rebalanced to prevent vibration or failure. Modifications from stock specifications may result in equipment failure, injury, or death. Such modifications should be performed only by qualified technicians. Contact your favorite shop for details. |
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