Piston Selection

^ Tools Required
- J 8087 Cylinder Bore Gauge

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





1. Measure the piston diameter and record the reading. When measuring piston for size or taper, measurement must be made as shown with the piston pin removed. If worn or damaged, replace with a standard or oversize piston.





2. Measure the cylinder bore, with the J 8087. If worn beyond specifications, rebore and hone to size.
3. If the cylinder bore must be reconditioned, measure the new piston diameter then hone the cylinder bore to the correct clearance.





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