They won't run without the air box.
You can make them run w/o the box but it is not worth the effort.
If you don't have it get one on FleaBay. Or get some up jets, and an open filter. Or get a a 20mm carb, and filter that is already jetted, and an open air filter for like 30.00 bucks.
That will get you 2-3MPH.