Here are a few usual suspects:
Change the in-tank fuel filter....they are old and made of paper and disintegrate, sending pieces of paper through the fuel line right into your carb. So you clean your carb, everything looks cool, reinstall, fire it up and in a few minutes, you're right back to where you were before.
Check needle and seat....most scoots have enough hours on them to have ridden to Alpha Centuri and back, twice, and these carb parts are usually way worn.
Check/lube your choke cable... sometimes it will stick 'on' even though the choke lever is down or off.
These are some of the quick and dirty ones. Let us know how it goes. Also, there are some really good scoot/sport threads over on mercurysnowmobiles.com
Good luck!
BHM