Mowerfreak,
Again it is the use of common sense as you would not apply full pressure at point blank range. Carburetors and exhaust are usually avoided as well as electrical systems. I have access to 4000 psi washers and they can do some real damage if used incorrectly. What Slashnburn used was probably something in the range of 2400-2700 psi if gas engine powered or 1800 psi if electric motor driven. These are a lot safer to use for engine and equipment clean-ups.
I do use the setup Speedy mentions to clean with 120 psi air except I do use an explosive mix of 50:1 of 2 fuel mix to cut though particular oily buildup on the engine exteriors as I usually in more a hurry due shop time constraints. This is done outside away from any potential ignition source. This is something I don't recommend as it can be very dangerous if precautions are not observed. Smoking is strictly forbidden at my shop.
