Ta Da! I'm gonna put my new standard answer... It's a cut paste deal. BUT Before that For ME: The reasons I tune are not to "gain 2-3mph" I tune because as Juice pointed out Kymco makes cookie cutter parts. MILLIONS of them. If you simply SPEC or BLUEPRINT an engine you will gain performance. The reason is tolerances. Say a cyl is .001 spec clearance... add 0005 variance, put in a piston with the same spec, and you are now at .002 or OUT of spec. by 001. JUST ONE example, and there is NO denying, or getting around it. I tune because I like the things I own to be the best it can be or I don't need it. So here is my cookie cutter answer...
Close your eyes, hold your breath, and jump in head first! Welcome to OUR world!
A few things to consider... How much do you like your scoot? Fits well, rides well, like the style? If yes to all... Is it just under powered for your needs? Tuning a BBK WILL take ALL your free time for several weeks. First finding the parts that will work, then finding the best price. Next comes learning all the "tricks" to preparing the raw parts for install. Now it's together... Getting the carb right for the new kit. That's done so you now have to tune the cvt to work with the carb. and BBK. If you are LUCKY that will be the end of it. BUT since you have learned Sooooo much about your scoot you may want to add a performance pipe. RE DO the carb to work w/ the pipe. RE DO the cvt to work w/ the new carb settings, and the pipe. Well yuo might as well do the air box now to really feel the new stuff. RE DO THE RE DO'S. Well now it runs better than any other scoot of it's type. Just noticed the OEM tires don't really hold that well... New set. Hmmm that rear shock feels "springy"... Where do you get those brighter headlights? Whats the best Ignition coil to use? Where the F' did my wife go?
If you have the time, and like tuning I say GO FOR IT!
You all will see this post again cause I'm copying it!
We can all help if you decide tuning is for you. Just taking the engine apart, and replacing out of spec OEM parts will give you a 4-5 mile boost if you know how to do it.