KX100 C series or D series - what's the difference

Check the frame for cracks or if its been welded up . There are a lot of little things to check for on any bike but on smaller KXs what comes to my mind is this : stripped drainplugs, broken/cracked R/S clutch cover where the shift shaft cracks the case in a fall, stripped shifter shaft splines. Loose spokes esp rear wheels , low compression . noisey motor piston /crank wear leaky forks etc. The newer carb is larger for an attempt at more peak powwer . And has a crescent shaped slide which can also add low end power . The older99 and newer 02/03 are pretty much alike except for the different carb and fuel tank and shrouds . They are good fun bikes and should be OK if you find one thats been maintained . GOOD LUCK in your search .