I have 6 gallons per minute water pressure and the pump still constantly surges. I have not been able to use it yet. Looks like the throttle is in a fixed position but there is no information other than the engine manual which says it should be adjustable. The web sight is unfriendly. Very low information. I waited to long to use it and found out the speed governing system is not designed properly and everyone seems to be having the same problem. No wonder they dropped the price. I won't be able to send it back so my only option is to do what Karcher should have done and modify the mechanism to work properly.
Pressure cycles high to low continually like it's not getting enough water. I am using 3/4" hose with 60 psi and no obstructions. Still on the first tank of gas.