Beogram 4004: DC Motor Restoration

I recently received two Beogram 4004 DC motors for restoration. This is the report on the first one. This shows the motor as received:

I disassembled the motor to get the bearings out for oil infusion. These motors use Oilite porous brass bearings infused with oil. After decades of service these bearings run dry (oil gets slowly extracted on the shaft as the motor spins). Luckily, they can be replenished by immersing the bearings into motor oil under vacuum. This shows the disassembled motor:

The bearings are the two small rings on the black pad. I put them in the oil and pulled a vacuum:

Immediately, bubbling started. This indicated that air is drawn from the pores in the brass material, making room for oil to diffuse into the bearing.

After about 24 hrs the bearing stopped and I extracted them from the oil:

I reassembled the motor and installed it into one of my Beogram 4002s. I ran it for 24 hrs, while logging the RPM in 10s intervals with my BeoloverRPM device (available to other enthusiasts - just send an email/message using the contact form). This is the RPM stability curve I measured:

This is as good as it gets...this motor is ready to spin some records again!