5-40 ENGINE TOP END
Piston Wear Inspection
Measure the outside diameter [A] of each piston 18 mm
(0.7087 in.) [B] up from the bottom of the piston at a right
angle to the direction of the piston pin.
If the measurement is under service limit, replace the pis-
82.969 ∼ 82.984 mm (3.2665 ∼ 3.2671 in.)
Service Limit: 82.82 mm (3.261 in.)
Piston Ring, Piston Ring Groove Wear Inspection
Check for uneven groove wear by inspecting the ring seat-
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 mea-
surements with a thickness gauge [A] to determine piston
Piston Ring/Groove Clearance
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
If the width of any of the two grooves is wider than the
service limit at any point, replace the piston.
0.03 ∼ 0.07 mm (0.001 ∼ 0.003 in.)
0.02 ∼ 0.06 mm (0.001 ∼ 0.002 in.)
0.17 mm (0.0067 in.)
0.16 mm (0.0063 in.)
0.92 ∼ 0.94 mm (0.0362 ∼ 0.0370 in.)
1.01 ∼ 1.03 mm (0.0398 ∼ 0.0406 in.)
1.02 mm (0.0402 in.)
1.11 mm (0.0437 in.)