K 3.86 M, UNIT SURGES WHEN WAND TRIGGER IS RELEASED

Have you tried servicing the motor. Fresh air filter, new fuel filter and a fresh spark plug? That will help narrow down what the problem could be.

Maybe press regulator was reset before the unloaded was installed and needs to be set at lowest and then increased as needed.

check for blocked jet at the wand end

indicates a blockage at the wand jet

If you are unable to shut off the pressure from the wand, there may be an issue with the unloader valve that is stopping it from switching into bypass mode when the trigger wand is released. The unloader valve is designed to respond to the spike in pressure created when the trigger wand is released, and to divert the flow of water coming from the pump to bypass the pressure hose and flow back into the intake end of the pump. If the unloader valve fails to switch into bypass mode, water may continue to flow out of the trigger wand. This may also cause damage to the wand. If you are unable to shut off the pressure from your power washer, stop the engine and discontinue use immediately. The unloader valve should be removed and possibly replaced if found to be malfunctioning. The inability to stop the flow of high-pressure water from the wand can be dangerous and should be fixed before continuing to use the machine.

spill valve is stuck and needs to be cleaned and greased common problem....also check all connections for blockage in line

Have a helper hold the trigger of the wand open while you try it again. If it starts that way you have a sticky unloader valve in the pump. DO NOT RELEASE the trigger for more than 10 seconds if the engine continues to strain when released! If the engine doesnt run freely when you let go of the trigger, pull it again and shut down the unit!
Add some power steering fluid to your supply hose (about 3 or 4 ounces at a time) and restart the unit with the trigger pulled. Allow the oil to flow through the pump for 1 - 2 minutes for each treatment. Several treatments should make the pump and valve happy again.

Hope this helps.

check filter in wand and clean out nozzle hole for starters

Re-kit the unloader.

common for not starting unless trigger engaged as you are turning the pump as well as engine creating pressure,as for stalling pump has unloader valve which is probably in need of grease(use good silicone grease)this allows water to ciculate when trigger released.