I have a Bachmann large scale loco that binds up on curves.  Runs fine on staright aways,but as soon as it goes in to curves it stops.  Seems like rear shaft is binding up.  How do I rectify this situation?  How do I know which way to turn drive shaft?
SgtMaj

I have a Large Scale 4-^-0 Bumble Bee locomotive and Im running on Piko track.  The curves are R-3 as well as the switchs.  The front truck derails on the curves as well as the switches.  Any idea why, And how I can prevent this from happening? I bgot this 2nd hand and someone glued some washes to weigh it down.