New air compressor gets loud and dims lights at 50psi

[Throwawrench]

So fellow tool lovers I've got a problem. Normally I get my info from searching old threads but this is something I can't seem to figure out myself.
I have a new, like 4 month old 30 gal oil lubed compressor from Minard's. Yes I know not the best but figured it would cut the mustard. It's done good for a while. It sounded funny for a few days and then dimed lights and was sounding loud. It runs and sounds perfect up till 50 psi then belt stops turning and compressor stalls. Any thoughts?
I did an oil change after about 5 hours of use, oil was very dirty. Belt tension seems good and pulley seems lined up. Correction the pulley moves when I turn it on. Just watched it move on the motor shaft. I realized that may need tightened but would that cause my issues or would that happen inspire of a bigger problem? The only modification is I have two lines coming from it one goes through a air filter and regulator. the other goes through just a half inch rubber hose to void air restriction to feed my impacts when I have a Honda crank pulley bolt or something along those lines to kill.

 

[Throwawrench]

Update before I tuted my own horn thought I'd investigate more. From the factory probably in China somewhere the motor pulley was not tightened on the shaft. So I pretended like I was a Chinese factory quality guy and I tightened my own bolts down and confirmed tightness of all seen fasteners. Wonder whats going on with ones I can't see?

 

[American Locomotive]

What was likely happening is the motor shaft would start slipping, the compressor would stop/slow down, and then because the compressor pump was in a loaded state (pressure pushing against the compressor head), the motor didn't have enough torque to get it spinning again when the shaft started to grab.

Compressors typically have a device called an unloader, which removes air pressure off the compressor pump for starting.

 

[Throwawrench]

I feel dumb because I didn't think to check tightness of pully. Thought it was a bigger issue than it was. I'm not overly impressed with the unit. It does what need it to do. Maybe it will do better with pulley tightened. Run time to get to pressure seemed to vary. I'm surprised it worked as long as it did. I did a timing belt two clutches and a timing chain using air tools with that compressor got through all those projects before pulley stoped

 

[Throwawrench]

BTW thanks for the info about compressors and responding to my Post. You guys always seem very willing to help even if someone is not on here very often