I just fixed my shifting problem. As I found on this site others have had this happen also. After only about 8 hours my new bike I lost my shifting, and the bike kept popping out of gear. I read other post about the shifting problem being due to a nut falling of the detent lever and spring. I checked with my local dealer and they were up front and honest with me about what it was and told me the same thing. WELL thats what it was. A really simple problem to fix if you have the right tools. First you must drain the oil, then pull the rear brake pedal off, then remove the right side cover bolts and cover. Next remove the clutch spring bolts and clutch disc.(this is where the "right tools" come into play) You need a clutch hub holder. Basically it is a clamp that holds the clutch hub still while you loosen the nut that holds it on. I picked up a Motion Pro tool for $35.00. You then remove the clutch hub and carrier basket. And in the bottom of the case I found my detent lever, spring, spacer, washer and nut. I dried my parts and located the threaded stud that the nut was attached to. It is behind the small sprocket just to the right of the large shaft the clutch was on. Mark the teeth of the sprocket to remount it in the same spot you remove it from. Remove the cir clip holding the sprocket on and remove the sprocket. I then got RED locktite and put it on the studs threads and on the nut. Place the spring and detent lever on the stud and torque to spec.(the service manual from the KX450F FAQ thread on the top of the forums first page really helped out) Then reassemble every thing, fill with oil and your back in business. I rode immediately after my repair and after about 10 min. of riding my bike shifts like a dream. I hope this helps someone else. Ohh yea, i took some pics. Email me if you would like to see the parts in a picture.