Spectrum K4 shorting on curves

[farrellrc]

Just got my new K4 Pacific and was immediately surprised when the loco shorted on one of the curves on my layout. This only lasted for a couple of seconds but long enough to restart the system. I found the front pilot wheel was arcing to the bottom of the cylinder which shorted the system momentarily. Close inspection showed pitting marks on the bottom of both cylinders (both sides of the loco). I finally put some Kapton tape on the cylinders and the problem stopped. What would cause this? I checked all the wheels for gage and they are OK. The pilot wheels pivot freely and don't cause any other problems. This is a real mystery to me as the engine was the only one of my 10 Bachmann Spectrum locos to do this. Also, this is happening on a 38-40 inch radius curve, which should not be a problem for a 4-6-2 loco. Any suggestions or comments.
  -Bob

[ebtnut]

Not being home and able to look at my K-4, but one thing you might look at is whether the pilot truck is turned around.  In a of lot cases the pivot slot on a model with a 4-wheel pilot truck is off-set slightly towards one end so as to give a bit more clearance so the front wheel doesn't do what yours is doing.  If it is turned around, it can short.  And yes, this should not be a problem at all on large radius curves.