hey lt. gust, I have no idea the answers to your questions, but I can offer theories or thoughts that I can think of.
first the 18 inch tire. I know they didn't last to long, my thinking is maybe they did this to change the rotational mass, rims are light and gobbs of rubber are heavy. so if they use an 18 inch rim and a lower profile tire wouldn't it decrease the rotational mass? if I'm wrong tell me, but when I look at pictures of guys racing my bike back then they don't look like they are leaning into the corners much, it looks like they are more concerned with the upcoming staights then the twisties, remember these are just thoughts.
ok as far as the v-4 goes, well there are several things I can think of, the first is better performance, see many engines are designed to run at peak efficency, not peak power, I have seen on several car engines before that if they add new cams and reverse the rotation they can get as much as an additional 15-25% power, but the cost is very high, on a bike it would be cheaper. my second thought would be maybe they wanted to move the running gear to the other side of the bike for better wieght distribution or to make clearence for an exhaust or something, what do you think?