Hey,
I'm an XR guy, with no experience with KLX's. Furthermore, I hate to start another oil debate. However, I have found that using a good 4-stroke motorcycle oil, rather than automotive type motor oils really helps to better lube the tranny and enables much smoother shifting. In my case, I use ProHonda GN4 (non-synthetic), and it was amazing the difference in the feel of shifting the first time I used it. After a 2 or 3 good rides, I can feel the shifting getting harder, so I know it's time to change the oil. Thumpers that use the same oil for the motor and tranny are able to break down the oil very quickly, especially with the added heat of aircooled XR's.
Tell your buddies to try a 4-stroke motorcycle oil if they don't already use it, and change it and the filter quite often. Otherwise, maybe you do have to grind on some of your tranny parts like mentioned above. Good luck.