Hello,
I would start with a new set of 6 gram rollers. Either Polini or Dr. Pulley rollers are good. Also a Malossi RED rear control spring. Get yourself a NEW Bando drive belt too. These are improvements over stock, and are the first things I would do on a used bike bike.
Torque settings on the Var nut make no difference in performance...
As suggested by Martfart, check/replace the small triangular bushes on the ramp plate in the var.. They are a wear item that needs replacing just like a belt.
When you replace the rollers use a small drop of motor oil or grease on the crank shaft, and inside the variator bushing. This is only to help these parts seat, and after that they "self lube".
Use a drop of Blue Lok-Tite on both the crank nut, and the clutch nut.
Get a new spark plug, air, and fuel filters, and start the bike.
Turn the idle mix screw clockwise untill you get the Highest rpm you can. If it only falls lower turn it Counter clockwise for the highest rpm. That's when you turn the slide control screw to get th recommended idle rpm.
i would carefully check the intake coupler to the carb for cracks or air leaks. These are the first part that fails on most Kymcos.
All of this will cost well under 100.00US, and will most likely have you going.
IF you have access to a leak down tester I strongly recommend testing for case leaks. The crank shaft seals do go bad, and most people sell bikes that have bad seals because they cannot figure why the bike runs sh**ty.
I would also do a compression test. You should see at LEAST 120 psi on this
Pressure Testing a Minarelli Horizontal 2-Stroke Scooter Engine
