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Cheap performance upgrade for a 50cc Chinese Scooter

While we were living in limbo over the summer, I bought a used scooter for my daughter to get herself to work.  The 2008 Roketa MC-17-50(SICILY-50) was slow. Dangerously slow. Going down a level road on full throttle, the speed topped out at 30mph unless I was going uphill (20mph) or downhill (40mph). At 2.9hp I wasn't sure if I was maximizing the performance.

I made a mental note to do something about the performance when I had a place to work on my stuff. 

Scooter internals were foreign to me.  They have a CVT transmission which I knew nothing about, however I quickly learned that the "Variator" is a neat little device driven by centrifugal force which works in conjunction with the centrifugal clutch to vary the gearing automatically as the rider goes down the road.

Like having someone change gears on my bicycle for me, the variator changes the front gears and the clutch changes the rear gears.

Online research pointed to several easy upgrades such as:
  1. removing the variator washer
  2. removing the exhaust restriction
  3. changing the jetting on the carb
When I began poking around, I discovered these performance restrictions did not apply to my daughter's scooter.

A little more poking and more google-fu and I discovered that I could change the gear shifting behavior by altering the centrifugal forces in the variator by changing the roller weights inside. 

These scooters come stock with 8.5g rollers which causes the scooter to upshift too soon and ensures the scooter never hits the meat of it's power band. I removed 3 of the 6 weights (making sure not to upset the balance) and took it for a spin to see if there was any difference from the seat of the pants and was pleased to find that the engine revs much higher now and I was able to hit 35mph on a gradual incline going up the street in front of our house.  Success!

On order are a set of 6g rollers. I decided to buy a new set of rollers instead of leaving them out in case the rollers need to apply some pressure as they do their business inside the variator and I figured 6 is better than 3 for balance, centrifugal force and potentially wear on the rollers.

I think I almost doubled my useable power for about $20.

Maintenance performed during the roller weight replacement:
-starter clutch replacement (the old one was getting a little slow in engaging, might be worthwhile spraying some lubricant in it)
-clean belt facing variator surfaces with brake clean and scotch bright
-lubricate drive shaft sleeve
-wax the variator roller surfaces (using spray furniture polish because I ran out of silicone spray)

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