Well, after advancing my timing to YZ in hopes to eliminate my 1/2 throttle bog/sputter I am still in the same boat. To summarize my efforts to date: Bike: 02' WR 426 YZ ex. cam w/ YZ timing (Im pretty darn sure now ) Air box lid off James Now BK mod (0.5 secs) Stock exhaust w/ Pro Moto insert Alt./Temp: 500-2500'/55-75F Combinations tested: -Stock jetting (165MJ, 42PJ, Stock needle clips 2-7) -Stock jetting w/ 168MJ, 170MJ, 175MJ. (All MJ's were tested w/ stock needle using clip positions 3-7) Items checked/cleaned: -Complete cleaning of carb (twice) -Baffle is clean and clear -Air filter is not over oiled -Fuel supply from tank is in order and the tank cap vent is clear. -Plug is fresh and gapped to spec Update: Today I tried out the new OCEMP needle from Sudco and my bog at 1/2 throttle is still there. With stock needle my slow circuit was spot on and I couldnt ask for better 0-1/4 throttle response but now with the EMP needle Im pretty sure Im running lean down low. I will bump up the pilot for that. As far as my top end sputter/bog I guess I'll check my electronics next. Cant see them going bad already, bike only has 200 soft miles on it. Any other ideas?