I forget what the name of it is but many of the body parts on K bikes are made of a white fiberglass-ish stuff that cracks when damaged. What I've found works well for repairing cracked body parts is to use a fiberglass repair kit (can be found at auto parts stores) to fix the cracked area from behind. The kits come with instructions and doing this sort of repair as a DIY job is pretty easy. Then fill and sand the outside of the crack.
Here's an example of a badly cracked K75 belly pan that I fixed. I used three layers of fiberglass to make it a beefy repair.
Before applying the fiberglass I scored up the area where the fiberglass was going to be applied with a Dremel cutting wheel and then cleaned it of with rubbing alcohol to maximize adhesion.
Since I knew I was going to have it coated in Line-X truck bed liner which would hide any minor inconsistencies I just did a quick and dirty fill and sand on the outside.
This RS had a broken windscreen upright and was my first fiberglass repair. I let the painter I hired do the fill and sand on that crack repair because they have the right filler and sanding stuff to do a professional repair job on the outside. After it's been painted there's no evidence that it's been repaired.
Anyhow, this is a good and easy way to save some $$$ when fixing up a K or other bike.
Tip: When mixing the fiberglass resin and hardener do not do it in a plastic or styrofoam cup. The mixing is an exothermic chemical reaction (generates heat) that welt melt syrogfoam or plastic. I usually use something like a glass salsa jar and throw it away after the job is done.
