I bought an 80-gal Husky tank that the former owner had put a Kellogg 2-stage pump on. Got it home, bolted it down, plugged it in. It makes a terrible clatter when it runs; I only ran it a few seconds. The motor is fine. If I didn't have so much time & effort in it I'd have taken it back. Darn thing weighs a ton.
I removed the pump and took apart the 4-pc head, didn't see a need to split the the crank case. There are no visible problems inside, nothing broken that would make such a racket. The pistons and cylinder walls are smooth. What could be making that awful noise? I'm afraid to run it for fear it'll explode.
It has a tag for the model # but it's been cleaned off with solvent. It has little reed valves if that helps pinpoint it.

I already put the head back together with silicon gasket material and I'd rather not crack it open again. So (sorry) you can't see the valves. When you disassemble the head they just fall out. I had a helluva time getting them to stay in their little grooves while I up-ended the head to put it back together.
It was filthy inside. The former owner had run it a good long time in a carpenter shop without an air filter.