The motors on these remind me of scalextric motors,
http://www.scalextricaustralia.com/S...or%20types.pdf
perhaps they are available with the appropriate length shafts?
example?
I am not sure if the brushes are the fault with these, but the
old type Johnson and RX motors, used to be able to opened up (the RX ones didnt need opened obviously) and their b
rushes could be replaced.
Then there is an interesting read
HERE, which I could see as being a problem with our locks (lack of cleaning/oiling?)