I only have had seven PS4002FK's, so I am no expert on these. But here is what I have had; All but one had starting problems
until I changed to 7 tooth pinions and 35 tooth crowns on the hardbody cars. Even after re-aligning the brush hoods, which I believe
is not the root cause. I had one with the can end bearing bound up on the armature shaft. This was fixed by shifting the bushing
around until the arm spun freely with the brushes out, and soldering it in from the outside. One started acting erratically in the middle
of a race. I checked the motor and could not find anything specific. But since I had removed, then re-installed the brushes, I can only
assume that there was a brush hung up in the hood. The motor ran fine afterward. This all on Mike Swiss's flat track.
I haven't had enough experience with these on the king track, but one of the other racers who does gave me a motor where the endbell
had completely melted, to see if I could figure out why. The bushing was free on the shaft, and still had some oil left on it, so I don't
believe the bushing overheated. Most of the distortion was on the legs between the bushing mount and the flange that fits into the can.
This allowed the arm to rub on the magnets. One brush was noticeably shorter than the other. I have found on some other PS motors
that the part of the spring which reaches from the spring post to the locking tab sometimes bears down on the top of the brush, and must
be bent slightly away from the brush. Otherwise, there is too much pressure on the brush and it binds against the comm. In this case, the
heat from the brush might have been transmitted through the brush hood and caused the endbell to melt.
In any case, I feel the manufacturer needs to get involved, because I don't see these problems as user created.