I totally agree with burn&file. Valves before anything. Once those are good, the carb mod is wicked simple and cheap. Get a Mikuni VM26 off ebay for $39 and get a jet kit for $10-20. Start with a 110 main. Once you get the carb tuned get a 17 in front. See if that is enough on the top end. If not grab a 45 for the back. I like my low gearing but I'm mainly off road. I like wheelies too
The bike has it's quirks but for the money they are great!