When I ordered a new motor from AMEL 2 years ago, this is what I got.
Maud told me the original MBT86 was not available anymore. I only realised the new one was smaller diameter when it arrived.
I used some 2mm rubber strip to wrap around the motor so it would fit more snugly in the black housing end piece.
It appears there is no way to service the brushes on these motors.