Gilera runner 172 roller issue

Hello guys im new here i have a gilera runner 172 specs are stock malossi 172 kit with pm proxy piston jasil 52mm full circle crank malossi variator malossi delta race clutch green springs malossi secondary gearup kit stock belt delly 25mm carb running 105 main jet airscrew 2 full turns out from closed idle screw 4 turns out malossi reedblock 24mm inlet manifold pm59 exhaust issue is ive tried 12.5g rollers 20by17 ones bike seems heavy from pulloff clutch dont bite floats upto 50mph but dont go above 60mph any advice would be appreciated