Runner VXR - exhaust and Rollers?

Hi I have a vxr 4stroke - it has a 200cc gearbox and a 180 engine, with a leo vince 4road pipe. my top end is about 70 mph this cannot be right? surely should be quicker than this?

it has 11.2g rollers in it and apparently it is meant to have 10.2g in it? can anyone shed any light on this for me? also what else could I do to increase the performance on this bike? I had a 172 2 stroke and it was way way quicker and top end was about 95mph.

any help would be great thanks

 

My Aprilia Scarabeo 200, with the 180cc engine, goes 80mph......and I put 11 gram Dr. Pulley sliders in it, for acceleration......if you put too light of rollers in it, your top speed is going to go down, not up!