Cylinder kit from Polini, big bore racing with a 52mm bore and a 29.2mm stroke, 84 cc with 1 poston ring. Polini Big evolution cylinders goes into the classes above the 70 ccm. With the Big evolution cylinder line,Polini has come out with 2 cylinders. The first is a 84 cc (with original 39.3 mm stroke) and/or 94 ccm. You will need to bore the engine case, see directions included for exact instructions on how to do this as per your model of scooter Performance-related to the 84-ccm-Version should be on the level of the 70-ccm-cylinders, however with clearly more torque. If you will want more power,who does not, you should go with the 94 cc version.