Compressor problems

[fred d]

I had a 3HP motor running a Quincy 216 compressor My dad had it when I was a kid and my best guess is that it’s close to 50 years old.
I went out one day and the compressor was not up to its normal pressure. Started to look at things and saw some black soot at the bottom of the base of the motor fins, and figure the motor head finally went out after a very long life.
Purchased a new motor installed it and it came on and ran great.
Went to use it today and realize that the compressor at 70 psi The pump seems to go into a bind if you will, and won’t continue to roll and the motor is acting like it is overloaded.
Turned off the breaker checked it out, pulled a relief valve to bleed off a little pressure at the top of the tank then tried to start it again and got about two revolutions before it stalled again.
After just dumping a bunch of money for a new motor I’d really hate to have to dump an equal amount for a pump.
But I need a compressor.
Below are a couple of pictures. Any help would be truly be appreciated

 

[FredWanaker]

don't know but I would pull the belt and see if the motor runs smoothly without overheating. Then I would try to rotate the pump by hand to see if it turns. The unloader valve could have gone bad, trapping compressed air in the compression chamber.

 

[The Cobbler]

when you shut the breaker off & released air from the tank, it most likely didn't unload the head so it would be trying to pump against pressure right away . that would explain that issue.
the reason it sort of binds at 70 psi? I am assuming you're using the same HP motor . belt tension is not too tight or too loose? belt and pulleys are aligned ? pump spins easily by hand with no sense of binding or bad bearings? check valve is not holding back air entering the tank and allowing the head pressure to build higher?

 

[fred d]

Wasn’t sure where to start looking. I will pull the belt and make sure that everything spins freely as it shoul.
the motor seems to run fine but I haven’t checked it running for any length of time time.
It won’t let me post a video here but I have a video of it running and experts might be able to diagnose by hearing it.

 

[MacMcMacmac]

Is the new motor running the same rpm as the old one?