Honda GX 120 Tech Manual page 5

H. Main jet and main nozzle:
Main Jet Size: maximum #70 (0.028) no
thru jet.
Main air jet: 0.0394" maximum #60 (0.040") no go - at back of hole.
Main jet access passage: 0.094" maximum #41 (0.096") no go.
Main nozzle:
1.
Main nozzle bore 0.069" maximum #50 (0.070") no go.
2.
Main nozzle will be checked with a NOGO Gauge ( 0.429") If gauge goes over dump tube – carb is illegal.. This is
best measured using a 0.452" rod type gauge with a 0.429" flat area to be used as a go gauge.
3.
Air vent holes on the side of the main nozzle must not be plugged.
4.
Main nozzle must not be fastened into the carburetor body by anything other than the main jet. It must not be
epoxied or positioned by any other means.
I. Slow speed system:
1. Pilot jet: 0.0138" maximum #79 (0.0145") no go.
2. Pilot air jet: 0.050" minimum 1.25mm (0.0492") go.
3. Pilot screw: no spec
4. Pilot seat diameter: 0.035" maximum #61 (0.039") no go.
5. Tip of pilot screw: 0.019" minimum.
J. Float bowl vent : 0.118" maximum #31 (0.120") no go.
K. Needle valve seat: 0.065" maximum #51 (0.067") no go.
L. The butterfly screw, the butterfly, and the throttle shaft must not be removed from the carburetor. Any evidence
of tampering will be a disqualification and suspension.
M. Decimal equivalents of numbered size drills chart on page 20
(MUST BE TIGHT)
go. Jets must be stock no stepping or funneling of jet No Go must not go
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