Vertex Sherco 290 Piston Kit

Piston Sizes

The factory recommended piston to cylinder tolerance for the 290 is 0.027 to 0.037mm, 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.

Please be aware that some of the 2011 - 2012 bikes came with a slightly larger piston, it is stamped 75.965 on the top, if you are replacing one of these you may need check the size of your cylinder to see if you can replace it with a size C piston.

These pistons usually come without the half moon shaped cutout on the bottom of the skirt on the inlet side, some Sherco's have the cut out some do not even straight from the factory, we find it makes no difference which piston you use.

18mm Gudgeon Pin by 52mm long
Centre of the gudgeon pin to the top edge of the piston 29.1mm
Overall height 68mm
Height from top to the edge of the piston 4.5mm
Weight including rings, gudgeon pin and C-clips 328 grams