Honda WB20X Water Pump Service Guide

Honda WT20 How can you get the most out of your WB20X? Even with Honda’s legendary reliability, this pump still requires regular maintenance to ensure years of trouble-free use.


Like any internal combustion engine, the WB20X’s motor produces carbon monoxide when it burns fuel. Always ensure there is adequate ventilation when running the pump, even if it will only be on for short periods during repairs.

Even when the pump is off, parts of the engine can still be hot enough to cause severe burns. Wait at least 15 minutes after running the engine before working on it.

Moving parts on a device powerful enough to move gallons of water pose a serious safety hazard, especially when performing maintenance. Never run the engine until instructed to do so until the repair is complete.

Always keep sources of flames and sparks away from fuel-related components.

Maintenance Schedule

– Before each use: Check the amount of oil in the engine and inspect the air filter for damage and debris.

– First month or 20 hours of operation: Change the oil.

– Every three months, or sooner when used in dusty areas: Clean the air filter.

– Every 6 months or 100 hours: Clean the sediment cup, fuel tank and fuel filter. Change the oil, and inspect the spark plug, adjusting the gap if necessary.

– Every year or 300 hours: Replace the spark plug and have a professional adjust the idle speed and valve clearance as well as check the impeller and pump inlet valve.


The WB20X holds 0.66 U.S. gallons (2.5 liters) of fuel. Always shut off the engine before adding fuel, and never fill the tank beyond the top of the filter screen inside the tank.

The WB20X can run on any automotive unleaded gasoline with an octane rating of at least 86. Light knocking and pinging is normal under a heavy load, but if this happens when the engine is running at a steady speed, try using a different brand of gasoline. If knocking still persists, have the engine inspected by a professional mechanic.


The engine holds a little over half a quart of oil. Honda recommends 10W30 works for most operating temperatures, but SAE 30 can be used if the engine is only run when it is 50°F (10°C) or higher, while 5W30 can be used if the pump needs to be used below freezing.

The oil filler cap/dipstick is located at the base of the engine. To check the oil level, remove the cap and clean off the dipstick. Place it back in the engine without screwing it in. Remove the cap and check the lines on the dipstick. If the level is low, add more oil. Any excess oil will flow out of the filler opening if the pump is sitting on a level surface.

The oil plug is located down and left from the cap. To change the oil, place a suitable container below the drain plug. Remove the cap and plug, letting the oil drain completely from the engine. Reinstall the plug, then add fresh oil. Replace the cap.

Air Filter

To remove the air filter, unscrew the wing nut holding the cleaner cover over the carburettor. Slide the cover and cover washer off of the intake, followed by the filter and grid. Take care not to let any dirt or debris fall into the carburetor. Reinstall in reverse order.

To clean the filter, wash it in soapy water, rinse, and let it dry completely. Wipe off the grid and inside of the filter cover with a wet rag. Soak the filter in clean motor oil then squeeze it to remove any excess oil. Too much oil in the filter may result in smoke coming from the exhaust when the engine is first used.

Sediment Cup

Before removing the cup, the fuel valve lever should be set to “Off.” Unbolt the sediment cup, located directly below the fuel lever and clean both it and the O-ring with a non-flammable solvent. Let the parts dry completely. Place the O-ring inside the fuel valve and screw the cup back into the valve. Set the fuel valve lever to “On” and watch for leaks around the O-ring.

Spark Plug

After disconnecting the plug cap, the plug can be removed using a standard 13/16 inch spark plug wrench.

The plug should be replaced if the insulator is damaged or the electrodes have worn down. Adjust the gap so that it falls between 0.028 inches (0.7 mm) and 0.031 inches (0.8 mm.) Clean the electrodes with a wire brush before reinstalling to ensure a strong spark. Honda recommends an NGK BPR6ES or Denso W20EPR-U spark plug for the WB20X.

When screwing the plug back into the engine, tighten 1/8 to 1/4 turn after the plug seats if it was used previously, or 1/2 turn if it is new to create a tight seal with the combustion chamber.

Spark Arrester

A spark arrester is optional on the WB20X, and can be added to the muffler if needed to comply with local fire safety laws.

To access the arrester, unscrew the two nuts at the muffler’s base and slide the muffler assembly off of the engine. Remove four screws holding on the muffler protector and separate it from the muffler. Finally, remove the single screw holding the arrestor inside the muffler. Follow these steps in reverse to reinstall the arrester.

Carbon deposits can be removed with a wire brush. Replace the arrester if it has holes or other damage.

Where to Buy Honda Water Pump Parts covers all of Honda’s small engine equipment including the WB20X. They carry every OEM part you may need for your pump from spark plugs to O-rings.

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