mine hits 170 (the fan switch) only when im going slow in trails, or up a long hill, which is quite often
i keep it jetted as lean as i can on the bottom without having it stall too easy
heres the biggest open spot on "the happy trail" , lots of logs and lots of deadfall left there to make it better

and by the tougher obstacles theres happy balloons, and theres people overheating, and people looking at a log thats across the trail level with their front fender going"wtf this is in the race", and people that just retuned their pipe... and happy balloons
without a fan ill boil if i stop at all when its hot out (on the happy trail), but if i keep moving and its not a mudbog, or up the side of a mountain in 1st for a mile i wont boil, without a fan
the 450 will have less power and will be harder to start, and will be heavier, but to make up for it it will require more maintenance.
4stroke=dead fish