INSPECTION


PISTON AND CONNECTING ROD ASSEMBLY
Piston Protrusion from Crankcase Top
    caution Do not fail to check piston protrusions. The engine performance are directly influenced by them.

    Standard value: 0.55 - 0.77 mm

1.Position each piston at the TDC.
2.Check for piston protrusions of each cylinder. There are five reference points A on the upper crankcase assembly. For each cylinder, measure the piston protrusion at the specified 4 points using the closest reference point as zero level. Average the 4 point readings.
B: Measuring point (16 in total)
3.If the average deviates the specified standard value, measure clearance at each section of piston, connecting rod and crankshaft.

    Standard value: 0.07 - 0.08 mm
    Limit: 0.15 mm

Connecting Rod End Play

1.Measure end play of each connecting rod.
2.If the measurement exceeds the specified service limit, replace defective part.

    Standard value: 0.15 - 0.45 mm
    Limit: 0.6 mm

CONNECTING ROD BEARING

caution
  • Be sure not to use the connecting rod bearings expanded forcedly.
  • When either one of the connecting rod bearings is replaced, replace both in pairs.

    Free Span
Measure free span of the connecting rod bearing s 4. If the reading is less than the specified service limit, replace both in pairs.

    Limit: 58.8 max


Connecting Rod Bearing-to-Crankshaft Clearance (Oil Clearance)
    If the reading exceeds the specified service limit, replace defective part.

    Standard value: 0.03 - 0.05 mm
    Limit: 0.1 mm

PISTON PIN / CONNECTING ROD / PISTON

1.Measure the clearance between the piston pin and piston. If the clearance exceeds the specified service limit, replace defective part.

    Standard value: 0.007 - 0.021 mm
    Limit: 0.05 mm

PISTON RING END GAP

1.Place the piston rings in the cylinder bore of the crankcase using the piston.
2.Holding the piston rings in this state, measure their end gap using a feeler gauge. If the reading exceeds the specified service limit, replace the piston ring.

    Standard value:

      No.1 ring: 0.3 - 0.45 mm
      No.2 ring: 0.3 - 0.45 mm
      Oil ring: 0.25 - 0.45 mm
    Limit:

      No.1 ring: 0.8 mm
      No.2 ring: 0.8 mm
      Oil ring: 0.8 mm
caution
  • In order to insert the piston rings level in the cylinder bore F of the crankcase, be sure to use the piston 9.
  • The piston rings must be placed at the less wearing bottom part of the crankcase cylinder bore F.
  • Replace the piston rings in a complete set.

PISTON RING TO PISTON RING GROOVE CLEARANCE


1.If the specified service limit is exceeded, replace defective part.
2.The first compression ring is a full keystone ring.Press it against the piston with a straightedge and measure the side clearance using a feeler gauge.

    Standard value:

      No.1 ring: 0.03 - 0.08 mm
      No.2 ring: 0.07 - 0.10 mm
      Oil ring: 0.03 - 0.06 mm
    Limit:

      No.1 ring: 0.15 mm
      No.2 ring: 0.15 mm
      Oil ring: 0.15 mm
3.
caution
  • Remove deposited carbon from all the piston ring grooves in the piston before measurements. Make side clearance measurements over the entire ring groove.
  • Replace the piston rings in a complete set.

CONNECTING ROD BEND AND TWIST


1.Install the connecting rod bush and piston pin into the connecting rod.
2.Measure the bend A and twist B of the connecting rod. If the readings exceed the specified service limits, replace the connecting rod.

    A: Bend
    Standard value: 0.05 mm
    B: Twist
    Standard value: 0.05 mm
caution
  • Install the connecting rod to the connecting rod aligner with the upper and lower connecting rod bearings attached.
  • Tighten the connecting rod cap by specified procedure.