MP40 repair help


New member
I bought an old MP40 from a friend who took down his tank years ago. It sounded like a lawn mower, and I found a thread on here to change the bearings, which I did.

I used:
uxcell 698-2RS Deep Groove
XiKe 607ZZ Precision Bearings 7x19x6mm

Before, running just the dry side alone was very loud. Now the dry side alone is almost silent, but still almost as loud as before when I run it with the wet side.

Has anyone tried any grease or lubricant inside the motor? I suspect the shaft/magnet inside the motor is making contact with the plastic. If this is the case, lubricant should quiet things significantly, and if it isn't, it shouldn't hurt anything.

Is my choice of bearings a problem?

Is it possible I have a different problem with the wet side and my dry side is fine?

Is it possible I put it together wrong, even though the dry side seems quiet alone?

This is a "generation 2" pre-QD MP40


Grizzled & Cynical
If the wetside is also pre QD then it’s well past tge replacement point. They chatter as they age.