Hi. the dealer i spoke to said that they replace roller weights, remove variator washer, new carb jet n remove airbox restriction. mine currently does 44 mph flat, smooth road, no wind, 47 mph downhill, redlining it. its done 2500 miles so well run in, its faster than the 1 at my dealers (by 13mph), they garantee with a de-res kit, it will do at least 65mph, but reckons it will do 75mph. apparently the factory top is 78mph. i also plan to get a 70/80 kit in the summer. hopefully add bit more muscle, maybe get it up to 80/90mph (fingers crossed), as i would carry passengers, on a full license ofcourse :)