There is no restriction on the s200. Your restricted by power, that's it. I have extensively tuned my girlfriends s200 and she hits 80 on the speed o no problem. The s200 has a tps based cdi so you don't h want to swap it, there is no "rev limit". If you want more top speed, the BEST thing you can do on the s200 is order yourself a Dr. Pulley variator I've seen them as low as $80 on eBay new. Also get 12g Dr pulley sliders. This will get you to about 70. Another great upgrade for that bike is a larger carb, both my gf and my cousin i have upgraded their carb to a 30mm cvk off of 250cc Kymco. This is the main upgrade in top speed but fairly expensive. A cam will help you too, but that is a pretty involved installation of you haven't done it before. The s200 had amazing potential and with a grand or so i could get it going 100mph pretty easy. All the parts I've listed will be four the gy6 engine, because the s200 shares almost all engine and trans parts with gy6, so if you order the variator make sure it says will work with gy6 150cc. Good luck, pm me if you need more tips! (Ps i have a 250 carb for sale too 😉)