A KLX is going to need a lot more than an additional 50cc to do the Full-Tilt Boogie.
I took the TE450 through some gnar-gnar at a good clip today, pretty much the first time I've tried to carrry some speed through tight, rocky & root infested singletrack with it. For a woodsie bike, that 450 was beating me to hell. The problem was primarily my throttle inputs -- I was turning the right grip too far, when I should've tried to even my pace out. I was smoked after only a few miles of
my race pace.
