Taken from Aaron's post in the rule change thread:

Quote Originally Posted by Kingpin
Suggest chage to section 2.2.3 Class displacement and configuration limits.

Section A: Middleweight super sport

Suggest changing From up to 600cc four cylinder
To. 640cc four cylinder

Reason is to allow for potential of 2013 zx6r just in case some one wants to buy one.
(P.S. no I'm not buying one) but thought it would be good not to restrict their new bike offering.
Questions I have -

1) Should the rule be re-worded: "up to 640cc as originally produced by the manufacturer"

2) Should overbore be allowed for motorcycles that were not produced as 640cc?