Piston Selection

^ TOOLS REQUIRED
- J 8087 Cylinder Bore Gauge

IMPORTANT: When fitting pistons, consider both the piston and the cylinder bore conditions together. Production and service pistons have the same nominal weight and may be intermixed without affecting engine balance. If necessary, used pistons may be fitted selectively to any cylinder of the engine, providing the pistons are in good condition and the same weight. Do not cut oversize pistons down or the engine balance may be affected. Finish hone when selecting the piston.





1. Measure the piston diameter and record the reading. When measuring the piston for size or taper, ensure that the measurement is made as shown when the piston pin is removed. If the piston worn or damaged, replace the piston with a standard or oversize piston.
2. Measure the cylinder bore, using the J 8087. If the piston is worn beyond specifications, rebore and hone to size.





3. If the cylinder bore needs reconditioning, measure the new piston diameter and hone the cylinder bore to the correct clearance.





4. Measure the J 8087. Record the reading.
5. Subtract the piston diameter from the cylinder bore diameter in order to determine the piston-to-bore clearance.
6. Compare the piston-to-bore clearance using the specifications in order to determine if the clearance is in acceptable range.
7. If a used piston is not acceptable, inspect the service piston sizes and determine if a new piston may be selected. Service pistons are available in standard, and 0.5 mm oversize.
8. When a piston has been selected, mark the piston in order to identify the cylinder for which the piston was fitted.