This comes up here once in a while, so I thought I would share my experience. Yesterday, Unisaw is working fine, then suddenly it will only hummmm and not start. Hmm, checked the breaker, voltage level, low voltage controls, etc. Nope, no joy, must remove motor.
These suckers are heavy and not easy to get close up and personal with.
Anyway, got it out on the floor. Tried it again, no spinnie, just hmmmmm.
So I take the bugger apart. Disconnect the wiring from the saw and get it up on a bench. Damn, how can so much dust get inside what appears to be a well sealed motor? What part of T-otally E-nclosed F-an C-ooled don't they understand? The junction box and the capacitor housings were completely full of fine dust.
The secret fix is inside the bell end of the motor. Took the bell off, took the fan off the shaft, take the tie rods out of the motor, mark the ends so we can get the alignment back correctly, then knocked the end cap off. The centrifugal switch area was completely filled with dust. Clearly the part that slides on the shaft was being held away from the switch contacts and holding the start capacitor connection open.
Blow that area and the whole motor out with compressed air. It looked like an Iraqi sand storm in my shop. Put it back together in reverse order and it works perfectly. Very straightforward to do, and any woodworker should be able to handle it.
Check the V-belts while you got it out. Easy to change them now if needed. Lifting the motor back in place is the hardest part of the whole job. Hang the motor with the sheave on the belts, then get SWMBO to push the pin in place while you hold the motor. You will enjoy this part cause you will need to snuggle up real close to get both of your bodies close enough.
This is the kind of thing that will always happen in the middle of a big project, but don't panic, if you are lucky it will be something this simple to fix.