I was wondering when you would chime in Gray. Great points. I grew up with an RM80 then stopped riding for 20 years due to loss of riding area and other life experiences. I returned to the sport with a 2002 YZ250F. It seemed easier to ride and my skills grew by leaps and bounds. I then moved to the 2005 YZ250 and remembered the need to control both the throttle and clutch for power management. I was slower around the track on the 2t than the "weaker" 4t. Partially due to the added chore of minding the clutch and partially due to the loss of my crutch the engine braking. Having felt confident with the 250F, I decided to move to the 450 and have never looked back. Had I not had the time aboard the 250F which allows longer rides with less fatigue, I may not have progressed to a confident 450 rider as the power is much more abrupt (even on the stock 09 Yamaha which is a pussycat) than the 250F. The extra ride time allowed me to develop excellent technique as I could ride continually making adjustments to my style and feel the difference immediately rather than get tired, take a break, then go out and make the same mistakes again. I will mention again one potential drawback of learning on a 4t vs a 2t can be reliance on engine breaking for corner slowing. I developed a nasty habit of allowing the bike to "coast" into turns and never used my rear brakes. I have been trying hard to break this habit as it will allow a much faster corner entry. Developing great braking habits is a huge step towards lowering your lap times as most size matched bikes accelerate at the same rate. The longer you are on the throttle and harder and later you hit the brakes the faster you will be. The 4t can retard the braking learning process if it is not addressed by a good trainer or natural instinct.