Sherco Top End Engine Rebuild Kit - 125cc - 2014 to 2019

Piston Sizes

The factory recommended piston to cylinder tolerance for the 125 is 0.02 to 0.03mm (or 0.04mm in the 2015 workshop manual), if you are considering putting the next size up piston in please be aware that your original piston will have worn down and any wear in the cylinder is unlikely to be uniform down the bore so please check the bore size all the way down the cylinder and from left to right as well as front to back, the factory measure the piston and cylinders at 24 degrees C. The piston is measured front to back and 19mm up from the bottom of the skirt, be aware that the pistons are manufacture tapered (larger at the bottom) and oval (larger front to back) to allow for unequal expansion of the piston in use.

16mm Gudgeon Pin by 47mm long
Centre of the gudgeon pin to the top edge of the piston 29mm
Height to the top edge of the piston 58.6mm
Overall height 61.6mm
Weight including rings, gudgeon pin and C-clips 186 grams

The base gaskets are available in different thicknesses to allow the correct squish clearance to be achieved. The standard gasket is 0.5mm thick and is commonly used with one of the thinner shim gasket, some bikes even come from the factory with 3 gaskets.

The factory recommend you set your squish (the gap between the top edge of the piston and the cylinder head) to a minimum of 0.50mm.