Im an KTM guy and have previously owned a few KDX's. I picked up a well used 97 200 with the idea of making it into a "second bike" while I do maintenance on the primary bike. Reading all the forum talk and the KDX tech stuff I wanted to build a decent trail bike with the knowledge learned here. I knew this bike needed some work but while changing the sprockets I noticed some play between a brand new countershaft sprocket and the countershaft splines. Did I get into something thats going to cost me more than the bike is worth? Is this a common wear issue? And, Is the gnarly wood pipe the best pipe for Eastern wood riding?
There should not be much play in the countershaft sprocket. The c/s sprocket should slide on easy, but there shouldn't be any sise-to-side movement. How did the old sprocket fit? Did it have the same play? If not, try a different manufacturer c/s sprocket.
Regarding the pipe, what are you looking for performance wise? Many seem to like the FMF Fatty. I like strong topp end power with a good mid-rev punch, so I use the PC pipe on my KDX.