GX22 GX31 Carburetor & Air Filter Tune-Up Kit

Key Features

• 4-Cycle Precision Calibration: Specifically jetted for Honda's small-displacement 4-stroke engines to ensure stable idling and high-torque performance without the need for oil-mixing.
• Enhanced Cold-Start Response: Features an integrated primer system and optimized internal fuel passages to provide reliable ignition even after long periods of storage.
• Complete Maintenance Solution: A comprehensive kit that includes a pre-calibrated carburetor, high-density air filter, fuel lines, and gaskets for a full fuel system restoration.
• Durable Alloy Build: Constructed from a high-grade, corrosion-resistant alloy designed to withstand the heat and vibration levels typical of tillers and blowers.
• Ethanol-Ready Internals: Equipped with modern diaphragms and seals engineered to resist the drying and cracking effects of ethanol-blended fuels.

Replaces / Cross-Reference Part Numbers

• 16100-ZM5-803
• 16100-ZM3-848
• 16100-ZM5-809
• 16100-ZM5-003
• GCA91

Compatibility & Fitment

This kit is the primary replacement for Honda's premium 4-cycle handheld engine series. Key compatible models include:

• Honda Engines: GX22, GX31, GX31N.
• Honda Tillers: FG100 mini-tiller and cultivator.
• Honda Trimmers: HHT25S, HHT31S, UMK431 series.
• Honda Power Equipment: WX10 Water Pump, HHE31C Edger.
• Note: Since these are 4-cycle engines, ensure you are not using 2-cycle "pre-mix" fuel, as it will clog the internal jets of this carburetor.

When to Replace

• Hard Starting: The engine requires excessive pulls to fire, indicating the internal primer or low-speed circuit is restricted.
• Loss of Power / Bogging: The engine starts and idles but dies or "stumbles" when the throttle is applied to engage the tiller tines or blower fan.
• Fuel Leaking: Gas is dripping from the carburetor throat or the primer bulb, which can lead to a fire hazard and poor fuel economy.
• Clogged Air Filter: The engine runs "rich" (black smoke or fouled spark plug) because the air filter is saturated with dirt or oil.
• Stuck Float/Needle: The engine floods constantly or won't draw fuel at all, often caused by "varnish" buildup from old fuel sitting in the bowl.

Installation Tips

• Fresh Oil Check: Since the GX22 and GX31 are 4-cycle engines, check the engine oil level while the unit is level before starting it with the new carburetor.
• Gasket Alignment: Pay close attention to the mounting gasket. If the pulse hole is blocked or the gasket is installed backward, the carburetor will not pump fuel correctly.
• Fuel Line Routing: Use the included fuel lines to replace the old ones. Ensure the "filter" line is in the bottom of the tank and the "return" line is just barely poking through the grommet.
• Purge the Air: After installation, press the primer bulb until you see fuel fill the bulb and flow back into the tank through the clear line to remove all air pockets.
• Avoid Over-Tightening: Tighten the two mounting bolts evenly to prevent warping the carburetor flange, which can cause an air leak and a "surging" idle.