Kawasaki J300 - Service manual > Piston Ring, Piston Ring Groove Wear Inspection

• Check for uneven groove wear by inspecting the ring seating.

  The rings should fit perfectly parallel to groove surfaces.

  If not, replace the piston and all the piston rings.

• With the piston rings in their grooves, make several measurements with a thickness gauge [A] to determine piston ring/groove clearance.

Piston Ring/Groove Clearance
 Standard:
  Top 0.015 - 0.055 mm (0.0006 - 0.0022 in.)
  Second 0.015 - 0.055 mm (0.0006 - 0.0022 in.)
 Service Limit:
  Top 0.13 mm (0.0051 in.)
  Second 0.13 mm (0.0051 in.)

Piston Ring Groove Width Inspection

• Measure the piston ring groove width.
  • Use a vernier caliper at several points around the piston.

Piston Ring Groove Width
 Standard:
  Top [A] 1.00 - 1.02 mm (0.039 - 0.040 in.)
  Second [B] 1.00 - 1.02 mm (0.039 - 0.040 in.)
 Service Limit:
  Top 1.1 mm (0.043 in.)
  Second 1.1 mm (0.043 in.)

If the width of any of the two grooves is wider than the service limit at any point, replace the piston.

Piston Ring Thickness Inspection

• Measure the piston ring thickness.
  • Use the micrometer to measure at several points around the ring.

Piston Ring Thickness
 Standard:
  Top [A] 0.97 - 0.99 mm (0.038 - 0.039 in.)
  Second [B] 0.97 - 0.99 mm (0.038 - 0.039 in.)
 Service Limit:
  Top 0.92 mm (0.036 in.)
  Second 0.92 mm (0.036 in.)

If any of the measurements is less than the service limit on either of the rings, replace all the rings.

NOTE

• When using new rings in a used piston, check for uneven groove wear. The rings should fit perfectly parallel to the groove sides. If not, replace the piston.

Piston Ring End Gap Inspection

• Place the piston ring [A] inside the cylinder, using the piston to locate the ring squarely in place. Set it close to the bottom of the cylinder, where cylinder wear is low.
• Measure the gap [B] between the ends of the ring with a thickness gauge.

Piston Ring End Gap
 Standard:
  Top 0.10 - 0.25 mm (0.004 - 0.010 in.)
  Second 0.10 - 0.25 mm (0.004 - 0.010 in.)
  Oil 0.20 - 0.70 mm (0.008 - 0.028 in.)
 Service Limit:
  Top 0.50 mm (0.020 in.)
  Second 0.50 mm (0.020 in.)
  Oil 1.0 mm (0.04 in.)

If the end gap of either ring is greater than the service limit, replace all the rings.

Piston, Piston Pin, Connecting Rod Wear Inspection

• Measure the diameter [A] of the piston pin with a micrometer.

Piston Pin Diameter
 Standard: 14.994 - 15.000 mm (0.59031 - 0.59055 in.)
 Service Limit: 14.96 mm (0.5890 in.)

If the piston pin diameter is less than the service limit at any point, replace the piston pin.

• Using a cylinder gauge, measure the diameter [A] of both piston pin holes in the piston and the inside diameter [B] of the connecting rod small end.

Piston Pin Hole Diameter
 Standard: 15.002 - 15.008 mm (0.59062 - 0.59086 in.)
 Service Limit: 15.04 mm (0.5921 in.)

Connecting Rod Small End Inside Diameter
 Standard: 15.016 - 15.034 mm (0.59118 - 0.59189 in.)
 Service Limit: 15.06 mm (0.5929 in.)

If either piston pin hole diameter exceeds the service limit, replace the piston.

If the pin hole groove shows excessive wear, replace the piston.

If the connecting rod small end inside diameter exceeds the service limit, replace the connecting rod.

See also: