Carburetor Modification For High Altitude Operation - Benchmark BW4400 Mode D'emploi

the pressure back to the factory setting turn the pressure regulator
clockwise until it stops.
Note
DO NOT try to turn the pressure regulator past the built in stop or damage
to the pump may occur.
DO NOT overtighten the regulator knob. This will result in an immediate
loss of pressure and costly repairs to the unit.
DO NOT attempt to increase the pressure above the factory setting.
Attempting to do so will void your warranty and may damage the pump.

5.5 CARBURETOR MODIFICATION FOR HIGH ALTITUDE OPERATION

At high altitudes, the standard carburetor air-fuel mixture will be too rich.
Fuel consumption will increase and performance will decrease. A very
rich mixture will also foul the spark plug and cause hard starting.
If using the pressure washer at high altitudes, change the main
carburetor jet or adjust the idling-screw of the carburetor. If always
operating the pressure washer at altitudes above 1,000 meters, contact
an authorized service center to have the carburetor modified.
Conversely, if the carburetor has been modified for high altitude
operation, the air-fuel mixture will be too lean for low altitude use.
Operation at low altitude my cause the engine to overheat and result in
serious engine damage. In this case the carburetor needs to be returned
to its original specifications.
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BW SERIES