If you were to search the forum for posts by me from early spring through late summer, you would see the agony my mobies put me through. I am glad I stuck with them. I love them now, and have 4. no other moped is appealing to me anymore. But the lows were really low.
It sounds to me as though your spark may not be strong enough to keep up with the constant flow of gas coming at it.
-Did you upjet?
-Bad Coil/Coils?
-Right Plug (I like champion L86c)
-Right Gap?
Or perhaps your condensor needs replacing (is it original?) my moby would stop firing after it heated up due to a old faulty condensor.
If you do not have this manual, it might help
http://mopedriders.org/article_view.php?faq=2&fldAuto=18
Good luck.
Italian peds are super easy to deal with if the moby is a lost cause