I've sold and ridden over 100 Speedfights in 2 years+ that I worked in a dealership and saw them come and go later with different mods and user experiences. One that "stuck" with me for a while was when a guy put in a rather cheap 68cc kit (I have no idea which manufacturer, but it was not the polini/malossi bunch) on a completely stock scooter. That bike was virtually as fast as the Speedfight 100 (air cooled 9hp, 2 stroke), and still quiet as stock. Funny thing is, the cylinder/piston kit was cheaper then the stock 50cc replacement. He did over 12k miles on it before I quit that job, so it was reliable too. That thing would spin the rear wheel (bare in mind that this scooter is only 200lbs or so) at full throttle from stand still. Ridden at a normal pace the fuel consumption also wasn't any worse then stock. I'd never use a sports variator or exhaust on mine. Mine DID come with the Leovince ZX pipe, but I took it off. The scooter had same MPG figures as my 650cc Kawasaki with it which makes no sense. Anyways, SF and SF2 were rather specific scooters and a lot of knowledge of different scooters doesn't apply here. The stock CVT and carb are good enough even with a tuned engine. I just wish Dr Pulley sliders were available back then so I could have experimented with those too as I have in my Downtown 300 (and it did wonders). Long story short, to the original poster, I'd get just slightly lighter rollers and take it from there. I hope there weren't many differences between different markets regarding CVT parts. I'm not sure if the stock weights on mine were 9gr, that sounds a bit high. I'm sure 5.5gr would blow the engine up in a few hours.