I ride nothing but tight HOT (it doesn't get below 80 here in the winter) single track trails with my '02 YZ426. once i switched to engine ice a year ago i have yet to experience any boilover problems. as far as mud pits go, i've learned to trust this bike & open the throttle. friend of mine has same year WR426 & only difference is his is slower...
I run Engine Ice
and I have found that I will not boil
over as long as there is at least some air movement over the radiators...even going very slow in 1st gear. When I am going to be in really tight stuff I run 13/50 gearing and that combined with the Rekluse
, auto-decomp cam, and a trials tire makes my '02 an excellent trail bike. Heck, I race harescrambles like that...on a really tight course the bike is unstoppable. Is it the most nimble bike out there? No, but the power delivery and the way it lays down traction more than makes up for it IMO.
When I ride in more open stuff I throw on a knobby and a 14 tooth front sprocket.