A few notes here - that motor drove me a little crazy when i got the machine.
First off - Lifting Stern PFs -
-- First rule - go slow and be careful. Stern resorted to lighter (cheaper?) parts here and it just doesnt feel as solid as Old B/W.
-- Lift PF up by the apron, and slide forward until the slider assembly "hits" the end of the bracket - all of that under the PF, the silver "arms" on both sides.
-- Pop out all four balls.
--Keep the PF centered while doing this, or you will scratch the sides.
-- Make sure the slider assembly is against the bracket before lifting the PF up! I know a guy whose Notch was over one of the brackets - when he lifted up, his PF fell into the cabinet and broke nearly all of the read playfield items.
-- Push the PF up toward the backbox, rest on the head.
The motor.
It varies by machine as to the sound. Sometimes, mine sounds like a jet engine. I see that the louder it gets, the more action i get off it, so i dont mind the sound. The sound is also drowned out by the games music, so i dont mind it as well.
The rubber disc "rests" on the motor shaft, the motor shaft just spins the disc. No magnets, its a pretty "simple" device, and the rubber disc should be completely balanced on the shaft. Any off side motion should be corrected. To check, just pull the PF forward (rest it on rails, or pegs), put the target bank down (via diagnostics mode), and get your hand in there - the disc should be flush with the PF.
When i got my game the disc wasnt wild. It spun, but the ball just wasnt getting any action off it. Heres what i did - and now that thing is AMAzING!
1. Wiped down the disc with a cloth with alcohol - the alcohol cleans and somewhat dries out the rubber, which gives a better grip to the ball.
2. Replaced the back rubber behind the disc with white - white rubber is bouncier and promotes more action off the rubber / onto the disc / disc gets ball faster now and flings it fast.
3. Oiled the disc motor - 3 in one oil, applied to a straw, top and bottom of the shaft, dropped a bit in. This promotes a faster spin.
After 100 plays, it all came together, and by far its the best toy in Pinball.