I have a Simpson PS3835 pressure washer with a Honda GX270 engine.
Background
When I was replacing the spark plug for the first time, the threads stripped out of the cylinder head as I was removing the spark plug. (Yup.) And I didn't use the pressure washer often during the winter, and the fuel stagnated. So, I replaced the cylinder head, carburetor, and all associated gaskets.
Problem
When I replaced the cylinder head, I adjusted the valve clearance to spec. I used the Honda service (not owner's) manual for the GX270 engine while I repaired it. I also used to be a Honda (automotive) mechanic, so I'm relatively comfortable repairing/rebuilding engines. All new gaskets everywhere for the cylinder head and carburetor.
Nevertheless, I cannot get this engine to start. I nearly ripped my shoulder out of socket, too. Ugh. So, I'm following the standard start up procedure as listed on the pressure washer. Gas valve set to ON, engine set to full choke. Fresh gas in fuel tank. Fresh oil change. Bleeding air out of all water hoses.
When I pull the starter cord, the engine is, for the most part, difficult to turn over. I know there are a lot of variables, but could there be something simple I am missing? Should I bleed air out of the fuel system at the carburetor? I don't know.
Update on 4/6/2020
So, I removed the cylinder head and then the valves. I pressed on the valves/valve springs to simulate them being opened, and it appeared that one of the valves was hanging. Hard to describe. Anyway, I removed, re-installed, adjusted valve clearance, re-assembled the cylinder head and carb. Now when I try to crank, it's like it was before this problem occurred. Much smoother, less resistance. I don't have time to hook up the pressure washer to test it out. I'll do that on Thursday. Update in a few days.
Update on 4/9/2020
I cranked the pressure washer today and it started up on the first pull. The problem was valve-related. I just had to remove and re-install the valves, valve spring retainers, and valve springs, ensuring that both valve assemblies moved freely. One of the valves was hanging up on the retainer, I believe.
Best Answer
Since this is a pressure washer and no one has mentioned it - when I have a hard time starting one, I will hold the trigger of the spray wand while starting so the pump can't build any pressure. Unless the engine is in perfect "start on the first pull" condition, this is a requirement because the pump will build pressure and make it harder for the engine to turn.
You used to be a mechanic, so I'm not going to talk about checking for fuel, spark and air - I assume you've done all that, so we are left with why the engine is hard to pull start and for me, its normally the compressor.