Honda GX 120 Tech Manual page 7

M. Decimal equivalents of numbered size drills chart on page 20
ENGINE COOLING SHROUDS
A. All pieces of the stock engine cooling shroud must be properly installed.
B. There must be no addition or subtraction of any material from the shrouding except for the covering of the switch hole (any
material). Starter cup may be altered to be used as washer retainer for the cooling fan.
1.
2.
3.
CYLINDER HEAD, HEAD GASKET, VALVES, SPRINGS
Remove cylinder head.
Head gasket thickness:
Measure from head surface to top of valve head:
This is best done with a depth micrometer or a bridge type dial indicator. Bridge type does not require removing
carbon from head surface. See photo on next page.
Combustion chamber cc:
Remove engine cooling shrouds. Remove valve cover.
Zero Dial Indicator after exhaust bump. (0.050) ref.
Maximum valve lift will be checked from the top of valve spring retainer. Valves may be adjusted to zero
clearance or shims may be installed to create zero clearance. This may dictate making special shims as it is
difficult to insert feeler gauge blades so as not to interfere with indicator contracts on retainer.
Valve lift:
0.040" minimum thickness of inner rim.
Intake:
Exhaust:
Intake: 0.245" maximum
Exhaust: 0.255" maximum
maximum 0.210"
maximum 0.210"
10cc ref. with stock spark plug.
minimum 0.178"
minimum 0.178"
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