First thing I would try a size or two larger main jet and buy a jet kit instead of paying per jet price like this kit
http://www.partsforscooters.com/114-...ategory=133078 Most of us do this first off .
How fast does it go ? How many miles are on it ? Ever had the valves adjusted ?
Prodigit is right as if its screaming at top end then even half a gram heavier would as well as if it is not redlining lighter weights would help .
I had a used Geo Metro with over 100k miles so instead of using 10w30 I tried 20w50 and man it did not perform as good . I drained it and went with 10w40 and it was way better . I opted for thicker oil since it had so many miles on it .
A performance variator often has steeper ramps and a larger diameter and has more top end .
My Echarm topped a 65 new and 70 after broken in . I replaced the 12.2 rollers with 12g DR Pulley sliders and gained 5 more MPH .
This place only sells GY6 parts and has performance goodies like high compression piston kits and more
http://scooterelements.ecrater.com/ More compression means more horse power .
I would skip the open airfilter since it means no riding in the rain . Many drill two holes in the airbox and rejet to get more flow and still prevent rain from getting into the carb and engine . A performance exhaust may have some gain and would also require rejetting which makes having the jet kit a great idea since you have the extras on hand if yo make mods