Bob:

If it rolls easily, it is not the counterweight.  I bought my second K from Caboose last April.  I had them fix the counterweights before they shipped it to me in Virginia.  It has worked perfectly since then.

Chuck N

Bob:

This sounds a lot like the counterweight problem.  Do the drivers turn freely and are the side rods straight across all four drivers, on both sides?  If you haven't replaced the counterweights or at least shimmed them, that could be the source of your problem.

Chuck Naeser