you dont need very many tools for the qt50. I own one myself.
Every thing on it is metric (its a japanese bike) The tools i use the most on it- 12 and 10 mm socket, and a philips screw driver. Thats about all :)
As for the carb cleaning- the carb on a qt50 is the simplest carb ive ever seen. There are only like 3 pieces that you take out of it to clean.
Take it all apart, and let all of the pieces sit ina container of gas (like a small coffee can) and let them soak for about 5-10 minutes. Then take it out, and use compressed air to blow thru all of the passages. Then re assemble
The qt50 is not the fastest bike around (27mph) but she will run for ever :)
If you have any other questions about the qt50, ask me, wayne, or just post it on the site