S3 Montesa Cota 315R Piston Kit

The factory recommended piston to cylinder tolerance for the 250 is 0.035 to 0.050 mm, 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 piston is measured front to back and 15mm 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.