I am thinking about changing to a 47 tooth rear sprocket for larger outdoor tracks with a few tight corners. Has anyone done testing of gearing set-ups for various track conditions? I heard that gearing-up helps with reducing rider fatigue and improving cornering for most outdoor tracks. I am concerned about stalling the bike or loosing time in the tight corners. I am an intermediate weighing in at 185lbs and I have increased the fly wheel weight by 4 oz. Your inputs would be appreciated. FYI. PowerNow works really well in both the 450F and 250F The Jardine RT4 exhaust system on the 450F is awesome. Better than FMF in my opinion. I bought both and sold the FMF. I also own an 03 250F. The improvement on mid and top from the Big Gun on the 250F are incredible. The bike screams on top like my old ported/polished YZ125's. I tried Dr D's and Yosh first but preferred Big Gun Race exhaust system.