Motor runs then stops

[Jyoung30]

Hey guys,

I have a 90s mark V with an Emerson motor. It will run briefly and then the motor just hums. If I take off the drive belt the motor runs fine, bit once the drive belt is on it won't run.
Below are the steps I have already taken.

Replaced drive and v belt
Replaced work gear and quadrant
Blown out motor to clear debris
Greased all bearings and control sheave.

It will periodically run and runs good. I am able to run it through all speed ranges, bit once I shut it off after either the high speed or low speed, the motor just hums and will perform 1-2 revolutions.

Thanks

[wa2crk]

Can you check the centrifugal switch in the motor? Some motors will run at a reduced RPM if it does not switch from the start windings to the run windings. There may be a thermal circuit breaker in the motor to save the windings.
Bill V

[Jyoung30]

How would I go about checking that?

Thanks for the help

[JPG]

First a nit-pickey detail. The start switch ONLY opens/closes the path to the start windings. The run windings are always energized when the power switch is closed.

Now since you 'blew' out the motor, you likely blew in trash onto the start switch contacts.

Try blowing around the terminal board from the internal side. Otherwise I fear disassembly will be needed.

Now belt on/off = no/run is a mystery???