Does anybody know how to adjust the pressure regulator oin 2600psi troy bilt?

Ok, first you don't ever want to start adjusting a pressure regulator on any pressure washer unless you have a pressure gauge on it. When you do the adjustments not only do you adjust the water pressure but also the back pressure when the trigger gun is not in use. You can destroy a unloader in a matter of hours with excessive back pressure.

Not knowing your exact pressure washer, most regulators have a large spring on it, with a knob or screw on the end, the pressure is adjusted by slight turning to cause the spring to tighten or loosen.

Also remember that a 2600 PSI pressure washer new from the box may not actually put out 2600, this is an @ figure, they can range up or down about 200 PSI and still be considered in range.

Also you can change the pressure of the water by different size tips, I don't mean red, yellow and green, that is only the angle of the spray, but all tips have sizes, if you go up or down a 1/2 size in the tip you can get several hundred more or less pounds pressure by merely changing tips. Tips should be replaced often on heavy used equipment, most professions will change their tips every couple months.

A pressure regulator is actually controlling flow. By increasing the spring tension you are forcing more water out of the nozzle and less into bypass. At some point you reach maximum flow (pressure) and tightening the knob does nothing.
To answer the question.. . Tighten the adjustment spring while your trigger is squeezed and you will feel the increase. Listen to your engine to make sure you don't run out of HP.

Please be very very careful if you merely "tighten down the spring"

If and when you release the trigger gun, you can get too much back pressure and destroy the seals in your pump. The back pressure is greater than the output pressure by a percentage at proper pressure, but as you tighten the spring the back pressure increases greater than the output pressure.

While it may not destroy the seals at one moment, it will shorten their life greatly. That is why you see a lot of home units, with water often coming out of the pressure relief.

And using the correct tip can change pressue by several hundred pounds very easily.

Nitrous...

I have a Husqvarna 3300 Pressure Washer. I want to lower the overall pressure of the machine for minor cleaning jobs. How do you adjust the pressure regulator? The plastic knob to adjust the pressure will not turn. I assume the pressure regulator is set at the maximum, but how do I turn it down? Does the machine have to be running to do so? It is almost like the company made it to where it is unadjustable, even though it is supposed to be adjustable.