BEMF is likely interferring since you have two motors.
Look up how to turn off regulated throttle and move it to standard throttle.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
How did it run before you changed the decoder?
Did you remove the noise suppression capacitors from the Bachmann circuit board?
Did you try adjusting any of thre CV's?
Newer Bachmann motors are very good. I'm not familar with that loco but have many other Bachmann locos. The motor is not likely the problem.
I would suggest removing the factory circuit board and hard wiring the decoder directly to the lights and motor.
Sheldon
I installed a QSI revolution and found the engine not to run smoothly.....took apart the trucks and looked at all the gears and everything looks ok. This model was the one that was released ~ 1 year ago with DCC on board.
Unless you have one of the really old Bachmann DD40X engines that had only one vertical (pancake) motor mounted right on the rear truck, there's no reason to replace it.
I've never found any reason to replace a newer Bachmann motor in any of their models -- they are can motors that run very well, Why do you think you need to change them?
I am pretty far along in detailing my new release Bachmann DD40X, including putting on proper grab irons, sand hatches, Microscale decals, and other assorted Detail West parts. I'd like to upgrade the motors in the engine - I realize there are 2 motors in this engine - has anyone replaced a Bachmann motor with a better performing model and if so can you share the manufacturer and model?
Thanks.