Piston Inspection

PISTON INSPECTION

Piston Inspection

Caution
^ Do not use a caustic cleaning solution or a wire brush to clean the pistons or damage may occur.





1. Clean and inspect the (A) ring lands, (B) skirts, (C) pin bosses, and the (D) top of the pistons. If wear marks or polishing are found on the piston skirt, check for a bent or twisted connecting rod.





2. Clean the piston ring grooves.
^ Make sure the oil ring holes are clean.





3. Measure the piston pin bore diameter in two directions on each side. Verify the diameter is within specification.

Note
^ Piston and piston pins are a matched set and cannot be interchanged.





4. Measure the piston skirt diameter as indicated.

Note
^ Always install the piston in the same cylinder bore from which it was removed.

Caution
^ Use care when fitting piston rings to avoid possible damage to the piston ring or the cylinder bore.





5. Push a piston into a cylinder to the bottom of ring travel using a piston without rings.

Note
^ Cylinder bore must be within specification for taper and out-of-round to fit piston rings.





6. Measure the top piston ring end gap using the Feeler Gauge.

Piston Replacement Inspection

Note
^ The cylinder bore must be within specifications for taper and out-of-round before fitting a piston.

1. Select a piston size based on the cylinder bore.

Note
^ For precision fit, new pistons are divided into three categories within each size range based on their relative position within the range. A paint spot on the new pistons indicates the position within the size range.

2. Choose the piston with the proper paint color.
^ Red-in the lower third of the size range.
^ Blue-in the middle third of the size range.
^ Yellow-in the upper third of the size range.

Piston Clearance Inspection





1. Subtract the piston diameter from the cylinder bore diameter to find the piston-to-cylinder bore clearance.

Piston Ring Clearance Inspection

1. Inspect for a step in the grooves.





2. Measure the piston ring-to-groove clearance all the way around the piston.

Piston Pin inspection





1. Measure the piston pin diameter in two directions at points shown. Verify the diameter is within specification.