Www Xr2500 Engine Manual
Gray fluid is usually indicative of old oil with water mixed into it. First you have to determine if the fluid is coming out of the motor or pressure pump. Then change the oil in that, or both, and then watch the condition of the oil when you use the washer. With new oil, it won't turn gray but will get a milky coloration to it. There shouldn't be any way for water to get into the motor oil short of the engine being sprayed directly with high pressure water.
If water is getting into the pump oil you'll have to check the seals inside the pump. Answered on Feb 14, 2013. I think you might be looking for the traditional brass flat head screw that is typically found and used to adjust engine idle.
This carburetor should have a black plastic knob that you turn to change idle speed. Look where the throttle cable attaches to the cam wheel on the carb.
Xr2500 Pressure Washer Engine Manual
The knob I mentioned earlier makes contact with that throttle cam. Please write back if there are any other questions. If by chance I misunderstood your request please provide more details regarding the problem. Also photos can be a big help too since sometimes different carbs are installed. Answered on Oct 20, 2018.