RVL
Amen brother
It's a damn shame the 500 class is gone :(
I sure wish archived lap times on common tracks were available, then a true comparison could be done (eg, Hangtown, Glen Helen, etc.) I've never owned a 250, but they say the handling is so much better, a 250 would supposedly beat a 500 on a tight track. I think another interesting comparison would be whether all this new technology is really working---what are 250 and 125 times today as compared to old? I'll bet they're not much different, but rather the tech. has allowed people to run the same speed with less of a beating.
And I wouldn't consider a YZ426F an "open" bike. Runs in the 250 class, and the middle of the pack at that. A true open 4 stroke would have to be at least 700cc based on previously discussed volumetric efficiencies, etc. I doubt they'll ever be made.
Jack