Ray,
if memory serves correct, you should be able to pop off the plastic cap on the bottom with a small flat-head screwdriver, though be prepared to catch the gas that will fall from the float bowl. the o-ring just slips over the plastic cap.
if this solves your leak problem consider yourself blessed, i ended up practically rebuilding mine while solving the leaks.
also... if it's one thing i've learned w/ these carbs, if you're gonna do one carb you might as well do the other.
and i also learned a lot from reading these docs:
http://www.sterlingbritishmotoringsociety.org/files/CarbsI.pdfgood luck, Steve