I'm in the process of doing the top end on my '90 kdx200. I've owned the bike for a year and so far it has been a strong runner. I've dis-assembled the s/a and given it a thorough cleaning. My question is what is the best method to clean out the stock pipe? Given the condition of the s/a, I am sure there is a lot of carbon build-up.
Try taking an old chain saw chain and run it in one end then the other and shaking then blow it out with air, works great. If you dont have chain saw chain you can use a bicycle or motorcycle chain as well, but the saw chain works best.