I bought a 60 gallon Craftsman air compressor off of craigslist last fall. It has great specs, 11.5 cfm at 90 psi. It is a 220v model.
When we went to check it out we ran it and it was loud lout loud. A real clack clack clak… You can’t talk to someone next to you. I thought this was the normal sound for large compressor and I bought it and we brought it back to the workshop. A friend who is building a Harmon Rocket has a new compressor and Dan mentioned it is really quiet compared to the beast I bought. Well I finally tore is apart and after consulting with Dan and some engine guys at work, the crankshaft bearings are scored and beat up. So I ordered a new set and we will see if that solves the problem. In the meantime I am cleaning it up from all the paint residue inside and out from the previous owner.
Interesting side note on the bearings. I could move the connecting rod back and forth on the crankshaft and wrist pin and clack against the shoulders on the crankshaft. The bearings are narrower than the width of the connecting rod and cap. But there does not seem to be any wear on the sides of the connecting rod and end cap, I assume the crankshaft would be harder than the others. I guess you would call this side play on the connecting rod.