Check with Digitrax.
  www.digitrax.com

 A friend and I each have K27's and of course they both had floppy counterweights.
We shimmed, or rather he did, both of them with .015 styrene. This is a real tight fit but worked perfectly.  Should last as the only load on the styrene is compression and it ain't going anywhere. Took about 45 minutes per K
Both K's run very smooth and look great double headed.
   Locoron

Thanks JD
I have one of the tanks and will have to check the parts bag.
Appreciate your offer.  Helpful people is a factor in making this a great hobby.
Ron

By the time I got around to gluing the K27 and freight car covers on I found I had lost one off the tender and one off a boxcar. Drat!
Are these going to be available in the near future?
May try to resin cast a few.

Got the thing apart and replaced LED with Miniatronics # 12-510-05 Yeloglo white LED. Much better than the anemic original.
All the innards come out the front so I carefully drilled a 1/8 dia hole in the rear cover.Then used a blunt tool to push, and ya really gotta PUSH, which popped out the lens, bulbholder and bulb. Installed new LED and then used a hole punch to create a small disc of thin styrene.  Glued that over the hole, painted it and it looks fine.
   Locoron

Bachmann deserves  the equivalent of the Nobel Peace Prise for the K27.
Beats the heck out of the $ 3000 engines.  However there has to be a nitpicker in the works and I be guilty. Didn't like the orange color on the classification lights. So replaced them with Miniatronics Yellowglow white LED's
What worries me is the headlight. If that LED burns out, which they  do once in a while, how the heck does the headlight come apart?

Received my K27 and a Sierra sound system on the same day. Stroke of luck.
Very pleased with both and the Sierra is reasonably priced.
  Locoron