yamaha neos 50cc 2002?

hi can any one tell me how to get a bit more speed from my neos as i have been told that they should do 50 to 55 mph and mine dose 42mph.i have put a new piston and head on it 50cc naraku.new variator high speed naraku.and a new exhurst naraku.as well the main jet is a 78 and rollers are 5g with red springs in the clutch.so any help would be nice.thanks lee