Take a look at
http://www.kymco-ersatzteile.de/shop/catalog/default.php?cPath=101_1579_514_520The roller weights (6) are sitting beneath the crankshaft (on its long left side in the variomatic).
They are separated in a cage (7) with a track which is narrowing to the outside (in respect to the diameter of the rollers).
If the crankshaft starts to turn, the rollers develop a centrifugal force according to their weight.
The centrifugal force drags them outside, so they push (5) towards (3), the belt (11) between those both pulleys moves up.
The counter force for the rollers centrifugal force is made by a big spring (without number above 12).
Weight and rotating speed make centrifugal force - more weight, less engine rotation needed (for the same transmission lenght).
The rollers move - move with friction makes wear.