you can do anything you want to the 749r or any 749 now that the dyno is no longer used as long as you don't make the motor bigger. granted you wont see a grid full of them because there isnt much money to win. that bike used to be excluded from the class only the 748 was allowed, but they decided to allow it since the dyno kept anyone from building one that would dominate the class, now the dyno is gone but the bike is still allowed. there is no doubt that is by far the best bike for that class. pegram rode one succesfully in ama fx in 2007 with a slightly bigger bore.