Kärcher HD 9/23 G service schedule

Pressure washers · Current model

Every maker's service job for the Kärcher HD 9/23 G, counted in hours, with the oils, filters and parts each one needs. Add your implement to Farmyard Workshop and it works out what's due from your hours and dates, and keeps the service history.

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Versions: HD 9/23 G (Honda GX390); HD 9/21 G (Honda GX340)

Service intervals

Job	When
Engine air cleaner clean or replace	every 50 hours or every 3 months
Engine oil change (Honda GX390)	every 100 hours or every 6 months
Fuel sediment cup clean	every 100 hours or every 6 months
Spark plug check and gap	every 100 hours or every 6 months
Spark arrester clean (dealer in Europe)	every 100 hours or every 6 months
Spark plug replacement	every 300 hours or every year
Idle speed and valve clearance check (dealer)	every 300 hours or every year
High-pressure pump oil change	every 500 hours or every year
Water filter and detergent filter clean, frame mounts check	every month
High-pressure hose, gun and nozzle check	when needed
Frost protection: drain and flush with antifreeze	when needed
Engine storage: drain fuel tank and carburettor	when needed

Service jobs and parts

Engine air cleaner clean or replace

Engine · every 50 hours or every 3 months

Honda's GX390 schedule says check the air cleaner each use, clean it every 3 months or 50 hours (more often in dust) and replace the paper element every year or 300 hours.

Part	Qty	Notes	Part number
Air filter element	1	Honda part number not found; check your handbook	check your handbook

Step-by-step

Remove the wing nut and air cleaner cover.
Foam element: wash in warm soapy water, rinse, dry, dip in clean engine oil and squeeze out the excess.
Paper element: tap it clean; replace it every year or 300 hours.
Oil bath type only: empty, clean and refill the case to the OIL LEVEL mark (80 cm³ for GX340/GX390).
Refit. Never run the engine without the air cleaner.

Tools: Warm soapy water, Clean engine oil

Engine oil change (Honda GX390)

Engine · every 100 hours or every 6 months

Kärcher says engine maintenance follows the engine maker's manual. Honda's GX390 schedule says change the oil after the first month or 20 hours, then every 6 months or 100 hours, and check the level before each use. There is no oil filter, so this task is oil only.

Part	Qty	Notes	Part number
Engine oil	1	Honda: SAE 10W-30 API SJ or later, 1.1 L. Kärcher lists 15W-40 as order no. 6.288-050.0. Aztec Oils match: AGRITEC LAWNMOWER 10W-30	6.288-050.0

Step-by-step

Run it only outdoors. The exhaust contains carbon monoxide, which is poisonous and odourless; never run it in a closed building.
Warm the engine, stop it and pull off the spark plug cap so it cannot start. Let the muffler cool.
Drain the oil from the engine drain bolt into a tray, refit the bolt.
Refill to the top of the filler neck (about 1.1 L per Honda) and check on the dipstick. Do not run below MIN.
Dispose of old oil at a collection point.

Tools: Drain tray (2 L), Spanner for the drain bolt, Funnel, Rags

Fuel sediment cup clean

Fuel · every 100 hours or every 6 months

Honda's GX390 schedule says clean the sediment cup every 6 months or 100 hours.

Part	Qty	Notes	Part number
Sediment cup O-ring	1	Replace if it leaks; check your handbook	check your handbook

Step-by-step

Outdoors, engine stopped, no flames. Turn the fuel valve OFF.
Remove the sediment cup and O-ring, wash the cup in non-flammable solvent and dry it.
Refit the O-ring and cup tightly, turn the fuel on and check for leaks.

Tools: Non-flammable solvent, Rag

Spark plug check and gap

Ignition · every 100 hours or every 6 months

Honda's GX390 schedule says check and adjust the spark plug every 6 months or 100 hours.

Step-by-step

Remove the plug, check it and clean it with a wire brush.
Set the gap to 0.7-0.8 mm.
Refit by hand, then 1/8 to 1/4 turn for a used plug.

Tools: Plug spanner, Feeler gauge, Wire brush

Spark arrester clean (dealer in Europe)

Engine · every 100 hours or every 6 months

Honda's GX390 schedule says clean the spark arrester (on engines that have one) every 6 months or 100 hours, and says that in Europe this should be done by your servicing dealer.

Step-by-step

Check whether your engine has a spark arrester.
If it does, have a Honda servicing dealer clean it every 6 months or 100 hours. They brush the carbon off the screen and replace it if holed.

Spark plug replacement

Ignition · every 300 hours or every year

Honda's GX390 schedule says replace the spark plug every year or 300 hours.

Part	Qty	Notes	Part number
Spark plug	1	Aftermarket: NGK. Honda specifies NGK BPR6ES; Honda's own part number not found. Gap 0.7-0.8 mm	BPR6ES

Step-by-step

Gap the new plug to 0.7-0.8 mm.
Screw in by hand, then tighten 1/2 turn to compress the washer.

Tools: Plug spanner

Idle speed and valve clearance check (dealer)

Engine · every 300 hours or every year

Honda's GX390 schedule says check and adjust idle speed and valve clearance every year or 300 hours, as dealer jobs.

Step-by-step

Book with a Honda servicing dealer; figures are in the Honda shop manual.

High-pressure pump oil change

Pump · every 500 hours or every year

Kärcher says change the high-pressure pump oil after 500 operating hours, at least annually, and have the machine serviced by Customer Service at the same time. Check the pump oil level weekly; if it is milky, call Customer Service.

Part	Qty	Notes	Part number
Pump oil	1	15W-40 engine oil, 0.35 L	6.288-050.0

Step-by-step

Before any work: set the engine switch to 0/OFF and remove the spark plug connector. Let hot parts cool.
Weekly: check the pump oil level in the sight glass. Do not run below the middle of the glass. Milky oil means water in the oil: call Customer Service.
To change: put a catch bin under the pump, undo the pump oil drain screw and drain the oil.
Refit the drain screw and fill slowly to the middle of the sight glass, letting air bubbles escape.
Have Customer Service carry out the annual or 500-hour maintenance.

Tools: Catch bin (about 1 L), Spanner for the oil drain screw

Water filter and detergent filter clean, frame mounts check

Pump · every month

Kärcher says monthly: clean the water filter and the filter on the detergent suction hose, and check the fastenings between motor and frame for cracks (have cracked ones replaced by Customer Service).

Step-by-step

Shut off the water supply.
Unscrew the union nut and remove the filter cup downwards. Clean the filter insert and cup, check the O-rings, reassemble and tighten the nut.
Clean the filter on the detergent suction hose.
Check the rubber mounts between engine and frame for cracks.

Tools: Spanner for the filter union nut

High-pressure hose, gun and nozzle check

Safety · when needed

Kärcher says check the high-pressure hose for damage daily (risk of bursting) and replace a damaged hose immediately, and check hose, gun and safety devices before each use.

Part	Qty	Notes	Part number
High-pressure nozzle	1	Size 048; Kärcher part number not given; check your handbook	check your handbook

Step-by-step

High-pressure injection injuries: a jet or pinhole leak can force water and dirt under the skin. Treat any such wound as serious and get to hospital at once, saying it was a high-pressure injection. (General first-aid guidance, not from Kärcher.)
Never point the jet at people, animals, live electrics or the machine, or at yourself to clean clothes or boots.
Wear gloves, goggles, protective clothing and hearing protection (this machine is 90 dB(A)).
Daily: check the high-pressure hose for damage and replace it immediately if damaged.
Stop the engine and squeeze the gun to release pressure before changing nozzles or hoses.

Tools: Gloves, Safety goggles, Ear defenders

Frost protection: drain and flush with antifreeze

Pump · when needed

Kärcher says freezing water can destroy parts of the machine. Store it in a heated room in winter; otherwise drain it and pump antifreeze through it.

Part	Qty	Notes	Part number
Antifreeze	1	Conventional frost protection agent; follow its maker's instructions	check your handbook

Step-by-step

Unscrew the water supply hose and the high-pressure hose.
Run the machine for no more than 1 minute until the pump and lines are empty.
Unscrew the water filter and empty it.
Pump conventional antifreeze through the machine. This also gives some corrosion protection.

Engine storage: drain fuel tank and carburettor

Fuel · when needed

Honda's GX390 manual says petrol can start to deteriorate in as little as 30 days. For storage either add a fuel stabiliser and run the engine 10 minutes, or drain the fuel tank and carburettor.

Step-by-step

Outdoors, engine cold, no flames.
Either add petrol stabiliser to a full tank of fresh petrol and run the engine outdoors for 10 minutes, or drain the tank and carburettor.
To drain: put an approved container under the carburettor, remove the carburettor drain bolt and gasket, and let the fuel drain. Refit the bolt and gasket.
Store the machine frost-protected (see the frost task).

Tools: Approved petrol can, Spanner for the carburettor drain bolt

Oils, fluids and capacities

System	Oil or spec	Capacity
Engine	Honda GX390 389 cc single-cylinder four-stroke petrol (HD 9/21 G: Honda GX340)
Engine oil	Honda says SAE 10W-30, API SJ or later, for general use. Kärcher's table gives 15W-40 engine oil, order no. 6.288-050.0 (see notes: conflict)	1.1 L (Honda GX390 manual); Kärcher's table says 0.9 L. No oil filter
Coolant	Air-cooled
Valve clearances	Check and adjust yearly or every 300 hours (dealer job); figure in the Honda shop manual
Engine oil	SAE 10W-30 API SJ+ (Honda) or 15W-40 (Kärcher 6.288-050.0)	1.1 L (Honda) / 0.9 L (Kärcher)
High-pressure pump oil	15W-40 engine oil, Kärcher order no. 6.288-050.0	0.35 L
Fuel tank	Unleaded petrol (E10 allowed); not two-stroke mix	6.1 L

Specifications


Working pressure	40-230 bar (HD 9/21 G: 40-210 bar)
Flow rate	530-930 l/h (HD 9/21 G: 250-850 l/h)
Safety valve	270 bar
Nozzle size	High pressure 048; low pressure 250
Max inlet water temperature / pressure	60 °C / 10 bar
Engine spark plug	NGK BPR6ES, gap 0.7-0.8 mm
Sound pressure level	90 dB(A): wear hearing protection
Operating weight	71 kg

Known problems

Carbon monoxide

Kärcher and Honda both say never run the engine in closed rooms; the exhaust contains poisonous carbon monoxide.

Fuel

Unleaded petrol only (E10 allowed). Never use two-stroke mix. Do not refuel with the engine hot or running.

Engine oil spec conflict

Honda's engine manual says 10W-30 and 1.1 L; Kärcher's table says 15W-40 and 0.9 L. Fill to the dipstick mark and follow the Honda grade unless your dealer says otherwise.

Repair guides

Petrol engine won't start or runs badly (Honda GX390 on the HD 9/23 G) (Easy, 20–45 minutes): Engine will not start, starts then stops, lacks power or speed so the pump will not reach pressure, or the wrong fuel has gone in.
Engine oil level, Oil Alert stop and the Honda/Kärcher oil grade conflict (Easy, 15 minutes): Engine stops and will not restart with fuel in it, oil below MIN on the dipstick, or unsure which oil grade and quantity to use because the Honda and Kärcher books differ.
No pressure, low pressure or pulsing: air, filters, nozzle and unloader (Moderate, 20–60 minutes): Weak jet, gauge low, pressure hunting up and down, machine cycling on and off with the gun shut, water bubbly at the nozzle, or no water at all.
Pump leaking or knocking: seal and valve kits, milky pump oil (Specialist, Owner checks 20 minutes; seal and valve kits by Customer Service): Water dripping from under the pump, pump oil milky, pump knocking or pressure unsteady even with clean filters and no air leaks, or oil leaking from the pump.
Frost damage: draining, antifreeze flush and what to check after a freeze (Moderate, 30 minutes (drain and flush); Customer Service for damage): Machine left wet in a frost; cracked pump head, water pouring from the pump or boiler, gun or hose split, no pressure after winter, or getting it ready for frost.
High-pressure hose, gun and lance leaks (and safe tyre cleaning) (Easy, 15–30 minutes): Water spraying from the hose, a bulge or exposed braid, drips at the gun or EASY!Lock joints, lance working loose, gun trigger sticking, or a tyre that discoloured or blistered while being washed.

The full step-by-step guides are in Farmyard Workshop once you add your implement.

Sources

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