Four Stroke Engine Superior To Two Strokes
A four stroke engine is a much better engine than a modern two stroke. I have raced MX for most of my life and the 4 stroke is a better bike all around. 4 stroke engines don't overheat, they don't have to mix gas, they don't burn as much gas, they don't spit out smoke and they don't sound like weed wackers.
The 2 stoke engine is faster like a 250 2 stroke is the same as a 450f however, in a top end race the 450f would come out on top, just like a 250f is faster then a 125 top end. The only reason they race in the same class is because 125 and 250 2 strokes are faster on take off and motocross racing is about getting there fast not like having a drag race.
2 strokes overheat on hot days, they burn too much gas, you have to mix it and they're just not as good as they were. I have raced people who have overheated their two stokes in a race.
So look around, no one uses 2 strokes anymore - only for tricks like Pastrana, Adams or Robbie Maddison. If your're going to race get a 250F or 450F, you'll enjoy it. It might cost more to rebuild but you don't have to rebuild it after every season such as 2 strokes, and if you're not racing but you're looking for a competition bike you'll enjoy four strokes. They're a lot smother and 10 x more reliable than guys who have been saying 2 strokes are better. They are wrong, everyone races 4 strokes and soon enough Yamaha and KTM will stop manufacturing them. Trust me I have been racing 125s, 250fs, 250s and 450fs and 4 beats 2.
Thanks for your time and have a good time on the track!