i have a new nrg.with arrow exhaust,malossi variator and clutch.i use 98 octan fuel& full syntetic oil.it can achieve more than 115,and 125 downhill.but soon i am going to install 80 ccm minarelli racing kit.more than 20 hp and 140 kmh possible.i did 15000 km in 5 months.perfect bike.lot of fun.no 50 ccm is match for me.if anyone needs a mods advice just ask.i am a doctor