I've been playing with my Dean's goods. It just needed pickups and final assembly. Well, pickups were duly fitted, then modified as I had a dead short on body.
I then connected the motor and it was very juddery, eventually I found a dead short on the centre drivers. The araldite had not insulated the large brass counter weights over the insulation gaps in the spokes. Off they came, and new plasticard ones went on.
Great, test on the track. Nope, juddery still, better backwards than forward. So out with the rolling road, take the wheels off, clean everything and reassemble, taking care everything was right before moving on. Put it on the rolling road, using wander leads, still the same, whilst head scratching, in one jerky movement the frames moved forward off the rollers, away went the wheels running smoothly. Well, me thinks let's try a new motor, the one I'm using is an 1833 Mashima, the 5th one in recent times that I've binned for lacking any get up go.
I put in a slightly smaller cheapie from Fleabay, it not only runs smoothly, it can run with the body on and move more than itself.
I used to have a supply of cannon motors which I can't replace since I moved abroad. Much better than the Mashima equivalent.