This is a great site that appears to be dominated by the k5 guys ! lots of good info that I've been wondering about for a few months now ! I used to race a yz 490 , then a cr 5 20 yrs ago , and decided to try and clear the big double and see what dirt tasted like on the other side of the fence ! so I gave it up and am now just getting back in a k5 with a 98 k5 525-530 ( whatever a 88 mm bore is ) . No more racing for me ! I have too much to loose now days , so I just ride in the u.p. of Michigan , Silver lake sand dunes , or in Wisconsin .