Honda GX 120 Tech Manual page 10

B. Measure from surface of head to top of valve guide.
C. Measure from surface of head to lowest machined area in the bowl of the port. This dimension will be:
D. Thickness of head. This will be measured from valve cover surface to head gasket surface at the side at a
position in line with upper intake & exhaust flange bolt.
Note: Most heads in the field have a thickness of 2.914.
INTAKE AND EXHAUST PORTS
A. Ports will be in "as cast" and factory machined condition and there must be no addition or subtraction of
metal or any other substance to the inside or outside of the cylinder head.
B. No alterations of any kind to be made to the intake or exhaust port.
C. This includes any grinding, polishing, etching, sand blasting or glass beading to interior surface.
D. Valve seats must be a stock single 45 degree angle. Multi angle valve seats are not permitted. Valve seats
must not be replaced.
E. Intake and Exhaust ports at valve:
Note: Cleaning of the combustion chamber or changing the finish of such chamber is illegal.
Maximum 0.265"
This dimension will be:
Intake 0.925 Max.
Exhaust 0.905 Max.
Intake: 1.063" maximum
Exhaust: 1.010" maximum
Maximum 2.917"
Minimum 0.2911"
Intake: maximum 0.752"
Exhaust: maximum 0.675"
Minimum 0.250"
0.925" Max.
minimum 0.745"
minimum 0.665"
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