Piston to cylinder selection

Estimated clearance between piston and cylinder (for new parts) is 0.05–0.07 mm. It is determined by measuring the cylinders and pistons and is ensured by installing pistons of the same class as the cylinders. Maximum allowable clearance (when parts are worn) - 0.15 mm.

Attention! The outer diameter of the pistons are divided into five classes (A, B, C, D, E) through 0.01 mm, and according to the diameter of the hole for the piston pin - into three categories through 0.004 mm. Piston class (letter) and piston pin bore category (number) stamped on the bottom of the piston.

If a used engine has a clearance greater than 0.15 mm, then it is necessary to reselect the pistons to the cylinders so that the clearance is as close as possible to the calculated one.

Pistons of classes A, C, E are supplied as spare parts. These classes are sufficient for selecting a piston for any cylinder, since pistons and cylinders are divided into classes with some overlap in size.