Doesn't it suck when you can't find some parts of a dis-assembled thing? Happens all to often around here.
No experience with the 250s, but the most important thing is the carb jetting. A lean mixture even in cool temperatures will burn up the top end. 100+ degreesF will add to need for a proper mixture. I got so skittish with my 350, I was rejetting every 10 degreeF change. That's changing between morning and afternoon rides the same day, and stopped melting pistons. Until I would get lazy, that is.
And because the performance loss of rich, I tended to leave it on the lean side.
Water cooling, properly set up, is a good thing. Over cooling is possible, but with our engine location, rarely seen.