VPI TNT 2

Your best bet is to replace the Hurst motor with an Anaheim Automation BLDC motor operated as a 3-phase AC synchronous motor. Link to DIYAudio thread below:

3 Phase Class D amp for DIY BLDC motor Drive

The Hurst motors are notoriously bad. I've built 5 or 6 of these SG4/MA3D AA motor setups and they work beautifully. I think there was a guy near the end of that thread who had a complete setup for sale. The BLWS motor is drop-in replacement for the Hurst motor but you need a different pulley. I use the following source but there are other options in the thread.

sdp-si.com

Let me know if I can help.