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I have recently acquired a MTH Railking F-3 from a RTR set.  Dual motored.  PS2.0   It runs in forward, both motors spinning.  When I hit the direction button (MTH DCS remote to put into reverse), it starts to move and the headlight turns off and the entire engine dies.  I can "rock" it forward by hand, and the light re-lights (and sounds come back), indicating to me that there is a short somewhere in the "system", but I'm guessing.  I took all parts off the chassis frame - everything - and couldn't find anything obvious.  I re-installed everything and it still does it.  I didn't try "rocking" all of the parts, but noted when I rocked the front can motor, it seemed to go in/out of "connection".  Note that this never trips any circuit breakers on the TIU or 180W bricks.  Any ideas?  Thanks in advance, Dave

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Everything looked very clean with no binding, but I'll check again.  I had it going forward and reverse around the layout a couple times without issue, but only after "rocking".  When it was going around, all the sudden minor sparks would fly out of the front wheels where they touch the rails, but only for an instant, and the engine kept running.  The sparks were somewhat disturbing.

 

I thought all screws were tight, especially after I re-assembled and the symptoms didn't change.

 

The part that is perplexing is at idle, with the light bulb burning and sounds going, when I put a finger on the front motor and push it gently towards the rear, it "rocks" a couple degrees, and the light and sounds shut down.  If I rock back forward, everything comes back on.  Behaves like something must be loose.

I'd say you are close to the issue.  Have you checked the motor mounting screw on the bottom of the truck?  It should be tight.  If the motor still moves AT ALL in relation to the truck, then maybe the two screws that hold the motor to the motor mount are loose. 

 

If either of these are true, it can cause it not to want to run in one direction as the torque changes the engagement of the worm.

You guys were right.  I took a more detailed look.  The front motor mounting screws were cross threaded and that was where the "rocking" was coming from.  After un-cross threading, I also noted that this motor would hang-up slightly.  Added some lube to the gears and it helped, but I still think the motor should probably be cleaned, too, just in case.  Not 100% sure it fixed everything, but I ran forward and backward about 20 times and there was no power-down.  Thanks, Dave

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