[SLESTAK75]

The CVT transmission can yield nice gains in overall performance with proper tuning. CVT weights and Contra springs are used to tune the CVT. Also the clutch and clutch springs. To understand how each of these parts affect performance it is important to understand what they do and how they interact. First of all it is important to know that tuning the CVT does NOT create power. The CVT transfers the power from the crankshaft to the rear wheels. A CVT that is not tuned properly can rob alot of power, so the objective is to create the most efficient transfer of power possible. The variator is a pulley in two halves. The outer half is stationary and the inner half is moved in and out by weights that run on ramps. The weights are thrown outward by centrifugal force as the rpm's increase. This causes them to ride up the ramps which pushes the pulley halves together. As the halves squeeze together it causes the belt to ride up the pulley faces. This in turn causes the belt to get pulled deeper into the rear "driven" pulley or torque sheave. The tension of the rear pulley is adjusted by the contra spring. Here is a link that shows a CVT shifting so you get the picture.

http://www.google.com/url?sa=t&rct=j...,d.dmQ&cad=rja

After looking at this video I wish I hadn't written so much but oh well. The heavier the weights in the variator, the quicker they are thrown outward and the lower the rpm's needed to shift. If you go too heavy your shift begins almost immediately robbing the takeoff power of the low gear. If you go too light you rpms will be higher as the shift occurs which gives you the benefit of the lower gears power for takeoff and climbing, but it is possible to go so light that the variator never fully closes which robs top end speed. This interacts with the spring on the rear pulley. The stiffer the spring the slower the shift and the more weight needed in the variator to accomplish a full shift. This is desirable when doing lots of hill climbing as the stiffer spring causes the CVT to downshift faster. A lighter spring will speed the upshift and slow the downshift and requires less weight in the variator to achieve full shift. This is desirable when constant cruising speed is your goal( such as in the case of a scooter). Most often a stiffer spring works better on a buggy due to its weight. There is no absolute perfect combination of components for the CVT. The components must be tested and catered to the preference of the owner. There is a range that seems to work best. Ultimately what I look for is the combination that gives the desired rpm thru the shift and still allows the CVT its full range of motion. Slider weights seem to perform better and last longer than roller weights. Most choose either a 1500rpm or 2000rpm Contra spring, and anywhere from 10gram to 14gram weights depending on the contra spring. 10-12 for 1500rpm 12-14 for 2000rpm. This is only a suggested starting point and beyond that the user will have to determine what they want. Higher rpm's = lighter weights. Lower rpms = heavier weights. A clutch with larger pads will grab and hold up better. Different clutch springs will determine when the clutch engages. Lower rpm rated springs will engage the clutch at lower rpms and vice versa. Please feel free to add if I missed anything.