I have an 05 YZF 450 here. Seems like it takes 10-15 kicks to start when cold. Also poor throttle response and severe bog when throttle is whacked open suddenly. Other than that bike runs good- great power engine sounds good idle-so-so. I checked the valve clearance and it was within factory specifications. I took the carburetor bowl off and it is immaculate. Bike is low hours-never raced.

I see this all the time. "yeah I cleaned the carb". Dont believe it.

Remove the bowl, clean out the pilot jet, the leak jet, the 1 way valves and then set the fuel screw to 2 turns out initially and tune. ALso remove the hotstart plunger, clean & grease it and then make sure the cable has slack in it. Make sure you can see through the jets after cleaning them