Ok, just to play devils advocate, the '01 YZ is a great bike! Really, I have no jetting issues at all in stock form. Its very forgiving on jetting based on temperature, runs great from 40 degrees out to 85. (Can't complain there.) The 38mm carb is notorious for making very little bottom end, however, that comes with a very distinct advantage: incredible topend power. If you riding skills include being good at staying on the pipe, the powerband issues won't hurt you at all. And it is a fact, in repeat tests, my '01 YZ125 will pull ahead and stay ahead of my buddies '03 KTM SX125, both in stock trim. So the YZ is making hella power! Great suspension, 6 speeds in the gear box (That would steer me away from an '02.) The KX in 2000 is a pretty decent bike, good motor. No experience with the RMs, and the Honda CR125s of the last three years, well, I've heard LOTS about issues of lacking power.