Hi I just bought a bachmann street  trolly it has the old style motor assy.I purchased it new from local hobby shop going out of business no refunds or returns. I opened the box myself it was still in the tissue paper .I took it out put it on the test oval of track it would not run. I then loosened the screws slightly on the motor box it started to run jerking and stopping. I then opened the motor box to find a cracked brush mount and  repaired it cleaning all oil from it and then using super glue.
I put it back together and got it to run without stopping but jerking as it went . I then tried it today it runs slowly makes and makes some grinding noise .I have another trolly same make and model. With a new style motor box no spring contacts on bottom. Old style has two spring loaded legs. Has anyone modified an older unt to run better? IF YOU HAVE PLEASE EMAIL ME WITH INFO