The engine runs strong. Mid to top end feels about the same as the 2008 crf450r. Off idle throttle response is impressive. Bottom end up to mid-range pulls stronger the the 08. No bogging, even if a gear hi. Feels much lighter than the 08 it feels light like a 2-stroke. It likes to be kicked twice to fire up and it don't like immediate throttle not a good combination for a hare scramble but maybe we can work that out. Springs and valving a little harsh for a 160 pound-er in the woods. That's been taken care of. Traction is phenomenal and it turns great. It seems to ride a little higher than the old bike but he thinks he likes that better. Haven't had in a actual race yet but some timed test suggest it may be good for 90 minutes on fuel but that might be a stretch. Hope to have oversize fuel tank with a quick fill in a few weeks. I miss the sight-glass for checking the oil, it has a dipstick. Can't decide what to do with the gearing I had the 08 geared down a little but this one has good snap and pulls the stock gear well. Planning to race this weekend that will tell the tale.