TaoTao ATM50 . . daily target for commuters and soccer moms . . improvements so I can really upset these people when I can pass them!
139QMB performance enhancements typically make the engine LESS reliable! Replace the scooter with at least a 125cc that is more compatible with traffic. Include the Bintelli 150's and Lance 200i's (169cc) in your research.
Why stop there Tortoise? I was thinking along the lines of a 283!! :-)
Unfortunately I do not have the room or the tools to be able to do any mods on the frame if the replacement engine does not line up but I was thinking along the same lines in the not to distant future!