1-S55
MX5100, WSM
ENGINE
[3] SERVICING
(1) Cylinder Head and Valves
Top Clearance
1. Remove the cylinder head.
2. Move the piston up and stick a strip of fuse on the piston head at
three position with grease.
3. Lower the piston and install the cylinder head. (Use a new
cylinder head gasket and tighten with a specified tightening
torque.)
4. Turn the flywheel until the piston exceeds top dead center.
5. Remove the cylinder head and measure the thickness of the
fuses.
6. If the measurement is not within the factory specifications, check
the oil clearances between the crankpin and bearing and
between the piston pin and bushing.
• After checking the top clearance, be sure to assemble the
cylinder head with a new cylinder head gasket.
W1020190
Cylinder Head Surface Flatness
1. Clean the cylinder head surface.
2. Place a straightedge on the cylinder head’s four sides (A), (B),
(C) and (D) and two diagonal (E) and (F) as shown in the figure.
3. Measure the clearance with a feeler gauge.
4. If the measurement exceeds the allowable limit, correct it with a
surface grinder.
• Do not place the straightedge on the combustion chamber.
• Be sure to check the valve recessing after correcting.
W1027737
Top clearance Factory spec.
0.575 to 0.675 mm
0.0227 to 0.0265 in.
Tightening torque Cylinder head screws
93.2 to 98.0 N·m
9.50 to 10.0 kgf·m
68.8 to 72.3 lbf·ft
(1) Piston (2) Fuse
Cylinder head surface
flatness
Allowable limit
0.05 mm
0.002 in.
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