I am 235# and I still turn faster laps on my 250f than on my 426. The '01 426 has become more of a burst motor that demands attention where the 250f needs no throttle adjustments. Feels like a light 250 2stroke that doesn't want to leap away from you at inopportune times. Pin and steer and ride for as long as you want. RosineJo if you are racing at outdoor tracks with longer motos you will have easy pickens of the tired guys towards the end. Shorter start straights the 250 will be right in the thick of things. I will be racing mine in one of the classes at Valley next Friday. Vet or Masters not really sure yet. Maybe 125B should be good for a laugh as I haven't raced inthe 125 class for twenty years.
I'm 180lbs, race in the senior novice class. This bike is making me a better rider, I'm definately faster on this bike compared to the '98 YZ400F I raced before, and it's more fun to ride and race. With that said, you will be at a SLIGHT disadvantage on starts and long staights. It will take some patience and adjustments to ride fast. If you hate 125's, this may not be the bike for you. Also, you will be riding this bike at full-throttle most of the time. Time will tell if reliability becomes an issue. I couldn't be happier with mine.
I'm 165 lbs riding 30+ B. Last year I raced the 426 and worked my way up to a top 5 finish after about 6 races. Always got extremely tired muscling the beast around though. Tried racing my son's YZ125 and it was much lighter and easier to save when about to crash, but I had to work very hard keeping it on the power band and gave up a lot on the start against the 250's. This year I got the YZ250F and I am loving it! Much easier to ride, throttle control is very sweet, much lighter than the 426, and it doesn't give up much to the 250 2-strokes. Most of the tracks that I race on are pretty tight, so I'm not giving much up after the start.
My wife bought me a 250F for Christmas, This bike is the best bike I've ever ridden. I'm 34 6' 225 and it has NO problem "haulin'" me around. In fact, I started back racing after a 12 year layoff and already collecting hardware for the mantle. I race 250 D and Vet Novice and am usually the first one to corner, even against 426's. I guess what I'm saying is after I get my 2002 250F everybody should have one ;)