My 250 was making nasty clacking noises from the top end. Checked and rechecked the valves...all in spec. Pulled the KACR, no change (other than the effort to kickstart). In desperation replaced the cam chain tensioner and exhaust cam.No change....Sheesh.... Yesterday changed the exhaust cam follower; the thing that actuates the ex. valves. The face was galled and scarred, making too much clearance with the lobe of the cam. Hence the racket. Now it sounds like new ! KLR's have notoriously weak cam-lobe hardening, and are prone to cam-face galling. I've heard the same noise in other 250's and have heard people say that a noisy top-end is typical from this bike. The lesson I learned is to always replace the follower with the cam as a matched set. It's an easy fix !