Can one update an M3 motor drive to M4 specification?

Absolutely.  The new drive system is available as a field install kit, or the grinder can be returned to Versalab for installation, for additional (labor) charge.

The cost of the kit is $525 + shipping.  It includes a new rear cover with the electronics already installed.  All five connections to the grinder are easily managed by hand.  Tools are provided to remove the original circuit board, and to accomplish the drive belt installation.

In addition a new small (motor) pulley and two belts are supplied.

See the downloads section in SUPPORT to read the installation instructions.