I found the clutch is actually more important than the vario. You wont see any MPH gains so it stays in the shadows. What you will see is the ability to hold the engine like a stretching rubber band, and release it at is strongest point.
It all begins with the shoes, and the bell. You must have a CNC cut bell to assure it is true, and aluminium is the best dissipater of heat. Semi Metallic shoes will GRAb when they are supposed to, and will not slip so they are also mandatory in my book.
Adjust-ability is the real key. Once your rollers are set you want the engine to spin freely untill it makes it's MAX power. Usually 7-9k on OEM type kits, and 9-12 k on race kits. You shouldn't even move untill this power is in. Thats where the fly spring work. Find the springs that hold the shoes in till you get to the power band.
Once you feel the shoes grabbing they should LOCK. If they dont... This is the job of the weights/spring retainer settings/or spring cams. Adjust these settings to allow the shoes to fly out with momentum
, and the clutch will lock.
When you start to roll you will feel when the rear pulley opens. When it is set w/ the wrong contra spring (too soft) the rpm will drop, and it will feel like a shift point.
When it is right the rpm will be steady right up to full throttle.
If it too stiff the bike will never get to top speed, and will rev like a demon
Even a stock scoot can benefit in drive-ability, take off, 0-whatever mph will be faster, and up hill lag will be cut to a minimum. Almost ANY vario will do its job. It holds rollers. Thats all.
The clutch delivers the power, and determines the performance of the engine. The more adjust-ability the clutch has is the key to eliminating all the variables between all our bikes, and rider weights.
Given a choice between a Polini jug kit, and a stage6 RtII clutch... I'd take the clutch. Every time.
There are lots of ways to make power but only one way to deliver it.
