Piston Rings/Ring Grooves

Check the pistons for uneven groove wear by visually inspecting the ring grooves.

If all the rings do not fit parallel to the groove upper and lower surfaces, the piston must be replaced.

Clean the piston ring grooves.

Fit the piston rings to the pistons. Check, using feeler gauges, for the correct clearance between the ring grooves and the rings. Replace the piston and rings if outside the specified limit.

Piston Ring Groove Clearance Check (capg)

Piston Ring to Ring Groove Clearance Check

Piston Ring/Groove Clearance

Top ring

0.02-0.06 mm

Service limit

0.075 mm

Second

0.02-0.06 mm

Service limit

0.075 mm

Piston Ring Gap

note
The piston ring gap, with the piston ring fitted in the liner, must be checked before final assembly.
  1. Place the piston ring inside the liner.
  2. Push the ring into the top of the cylinder, using the piston to hold the ring square with the inside of the bore. Continue to push the ring into the bore until the third groove of the piston is level with the cylinder top, around the full circumference of cylinder.
    3. Cylinder Liner (cduo_3)

    Aligning Piston Rings using the Piston

  3. Remove the piston and measure the gap between the ends of the piston ring using feeler gauges.

Piston Ring End-Gap Tolerances

Top

0.15-0.30 mm

Service limit

0.42 mm

Second

0.30-0.45 mm

Service limit

0.57 mm

Oil Control

0.20-0.70 mm

Service limit

0.84 mm

note
If the end-gap is too large, replace the piston rings with a new set.If the gap remains too large with the new piston rings, both the pistons and barrels must be replaced.If the gap is too small, check the cylinder bore for distortion, replacing as necessary. DO NOT FILE PISTON RINGS!