ENGINE TOP END
3-5-32
Piston/Cylinder Clearance
Piston/Cylinder Clearance
◆
Subtract the piston diameter from the cylinder inside
diameter to get the piston/cylinder clearance.
Piston/Cylinder Clearance
Standard: 0.051 ~ 0.069 mm (0.0020" ~ 0.0027".)
Piston Ring, Piston Ring Groove Wear
Piston Ring, Piston Ring Groove Wear
◆
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 to determine
piston ring/groove clearance.
Piston Ring to Groove Clearance:
Top Ring:
0.020 ~ 0.060 mm (0.0007" ~ 0.0023")
Second Ring:
0.020 ~ 0.060 mm (0.0007" ~ 0.0023")
Service Limit:
0.12 mm (0.0047")
If the piston ring groove clearance is greater than the
service limit, measure the ring thickness and groove
width as follows to decide whether to replace the rings,
the piston or both.
Piston Ring Groove Width
◆
Measure the piston ring groove width.
○ Use a vernier caliper at several points around the
piston.
Piston Ring Groove Width
Standard Service Limit
Top:
Second:
1.22 ~ 1.25 mm
(0.0480" ~ 0.0492")
1.32mm
(0.0520")
If the width of any of the two grooves is wider than the
service limit at any point, replace the piston.
Piston Ring Thickness
◆
Measure the piston ring thickness.
○ Use a micrometer to measure at several points
around the ring.
Piston Ring Thickness
Standard Service Limit
Top:
Second:
1.17 ~ 1.19 mm
(0.0461" ~ 0.0469")
1.10mm
(0.0433")
Measure Here
Measure Here
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