there is a rumor going aroung that yz250f thumper can run the 125 class
ONLY if you are a pro rider amatures and beginners have to ride the bike in the 250 class
IS THIS TRUE?????
whats the actuall rules on this bike?
I'm not sure of the specific displacement of the bike, but if it's 250cc or less, it must be run in Class 1 (the class for 86cc-125cc two-strokes). If its displacement is just over 250cc, then it must be run in Class 2 (the class for 126cc-250cc two-strokes). This is from the 2000 AMA amateur rule book, page 14.
James is right on the money and that is from the "00 AMA Amateur" rulebook.
So as the rule now stands ( which COULD change at AMA congress this October)
That bike for AMA amateur competition ..is in the 125 class if 250cc or under.
If its above 251cc it would run in the 250 class.
On this subject it is exactly the same as the 00 AMA Pro rulebook.
I plan to ask at Congress what if a 4 stroke bike is 250.5 cc what class is it legal in? lol
I'm sure you will see that rule clarified
Yamaha now has info on the YZ250F on their website. They're listing the displacement as 249 cc. The bore and stroke are 77 X 53.6 mm, which comes out to 249.6 cc by my calculations. Looks like Yamaha read the rulebook before they got started on this project.
Other intereting things to note: the bike has a HUGE 37 mm carb, and it's running a 12.5:1 compression ratio, just like it's big bro. Yamaha isn't listing the bike's weight at this time.