Well I am normally on the 250F but I need a little info on the 450F. A guy I know (who is used to riding old school yamahas) just bought a new WR450F (an 03 I believe). He had the dealer put on the exhaust tip & throttle stop, but other than that he is not sure what else they did as far as jetting or grey wire. He said the thing has got "no low end". It sounds crazy that a 4 stroke 450 would be lacking in the low end dept. I am assuming that it is a jetting/carb problem. The things want to stall at low RMP and is a pain to start. My husband did the grey wire on his 250f and loved the difference. My brother-inlaw did it on his 426 and hated it because he lost a lot of low end, and sputtered at low RPM's. Did any of you feel that you lost low end after cutting the grey wire? We are planning on tearing apart the carb and seeing what in there. We are assuming we may need to just richen the pilot, maybe the MJ, and go from there. I am going to see If I can talk him into the JD jetting kit. We will also check the grey wire. How does the WR450F low end torque compare to an XR400? I know I am comparing apples to oranges, but the race bikes perform with better responce and Yamaha's are known to hit harder. If you are used to old school smoother more gradual power, maybe it feels like it has less smooth low end. I am just guessing here. Any advice you can lend is much appreciated.