Greg E. alerted me to a problem in the K-4 pilot truck which can contribute to derails. He has this fix documented at his website found at
www.elmassian.com/index.php under the "Misc. info/tips" link.
The shoulder bolt that holds the pilot truck has a sharp lower edge on the head, which can gouge into the sliding surface, causing a bind and subsequent derail. The fix, is to
1. remove the truck,
2. use the bolt head to remove all paint from the sliding area,
3. remove the sharp edge by sanding/filing the backside of the bolt head while chucked in a drill,
4. Lube area with moly or graphite grease,
5. reassemble with washer and spring.
Greg also suggests placing three #4 washers around the threaded portion of the shoulder bolt to increase possible downward travel.
While performing the above, I discovered another issue with the shoulder bolt that required correction.
The edges of the slider slot had burrs on them, causing the bolt to bind in the middle and at the extremes of movement. I filed down the slot as shown in the pictures.
Now the pilot moves much smoother throughout its travel, without binding.
Re-assembled Pilot truck.
This last pic is for those interested in seeing the underside of the K-4. The track pickup wires are easily seen.
Jim C.