I bought a 3/4 hp bench grinder, Asian type, 1/2 inch shaft cheap because it was MISSING the capacitor that normally fits inside the hollow area of cast iron base.
I took it to our local electric motor repair place here, and they brought out a very large capacitor that was way too big for under the base.
So,,,I mounted the capacitor behind the grinder on a plywood base for the motor, and ran the wires up inside the motor.
It now starts instantly, and has as much wheel power that I can stand without danger.
So, if you have to you can mount a capacitor outside,, instead of trying to cram it all up inside the base of the grinder motor.