Cylinder Diameter Measurement Diagram
- A, B - measurement directions
- 1, 2, 3 - measurement belts
Piston identification
- a = 8.1 mm, mod. DR
- a = 4.4 mm, mod. D.S
Order of execution
1. All parts of the connecting rod and piston group must be cleaned and washed with gasoline.
2. Check pistons. Measure the piston skirt diameter at a distance of 15 mm from the bottom edge of the skirt, perpendicular to the axis of the piston pin. The piston must be replaced if the measured diameter differs by 0.04 mm from the nominal diameter of 80.98 mm. To measure the clearance in the piston ring lock, insert the ring into the cylinder and advance the piston, like a mandrel, to a distance of 15 mm from the base of the cylinder. Measure the gap in the lock with a feeler gauge. If the gap exceeds 1.0 mm, the rings must be replaced.
3. Measure the backlash between the piston rings and the grooves on the piston at several places along the circumference. If the gap exceeds 0.15 mm, replace the rings or pistons.
4. Measure the diameter of the cylinders with a bore gauge, as shown in the figure Cylinder Diameter Measurement Diagram. The diameter of each cylinder is measured at six points, 10 mm from the bottom of the cylinder, 10 mm from the top of the cylinder and in the middle in two perpendicular directions. If wear from a nominal diameter of 81.01 mm exceeds 0.08 mm, bore the cylinders to the repair size. If wear reaches the limit in only one cylinder, all four cylinders still need to be bored, otherwise the engine will not be balanced.
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