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I know we all don't use pressure washers on roofs but alot of us have them and use them elsewhere. I got a pressure gauge yesterday and tested both my machines.

One is a honda 4gpm 4000psi belt drive unit (no stickers or numbers on machine, thats just what I was told). Test results: With the unloader fully tight the operating pressure was 3500psi under load with all the tips but the pressure would jump to 4800psi when I let off the trigger. I adjusted it down so that pressure only jumps to 4000psi and operating pressure is still at 3500psi. If I adjust any lower I will start to lose operating pressure.

The other one is my old 3000psi 2.7gpm. Test results: Same as above. Operating pressure is 2500psi and jumps to 3000psi when I let off the trigger.

So does this sound normal for pressure washers? I've see larry's video on adjusting the unloader so this seems normal to me.

Is my machine really a 4000 or 3500? I think 4000 because both machines have operating pressures 500psi lower than they are rated for.

Sounds like you're on the right track. The pump on the bigger machine is most likely either a 3.5gpm @ 4000 or a 4gpm @ 3500. Both sizes are pretty common. Either one will make you the money . I get a 200 psi drop on 200' of hose. The pump should have a name on it somewhere, along with a serial number. I used one of those machines to put food on the table when I first started. Not the fastest machines in the world, but more than capable to do the job with the right person behind the wand. I'm always glad to help if I can. Congrats on the new setup!

If with a "PROPERLY FIT" unloader your gauge jumps to 4800, that's because you have it slam bang tight. When set to 4000 it's set right. You can not go by what tip is in, you go by where it stops at-as you have done. I have an 18hp 4000 psi machine, but turn it down to 2500 psi. I don't want to blast most things, I want the extra water flow. You can't have high water flow and high pressure-CHOOSE.