Honda GX120 Owner's Manual page 26

SERVICING YOUR ENGINE
MAINTENANCE SCHEDULE
Emission-related items.
*
Internal vent carburetor (See page 7
)
with dual element type only.
(Cyclone type every 6 months or 150 hours.)
* *
Replace paper element type only. Cyclone type every 2 years or
600 hours.
(1)
Service more frequently when used in dusty areas.
(2) These items should be serviced by your servicing dealer, unless
you have the proper tools and are mechanically proficient. Refer
to Honda shop manual for service procedures.
(3) For commercial use, log hours of operation to determine proper
maintenance intervals.
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