Hm. On my bike, the drain screw is accessable from the right, not the left, and you can reach it when the carb is on the bike.
Ben - If gas comes out of the tube when it is pointed down:
A. Too much fuel is pouring into your carb
B. Your drain screw or the rubber ring on it is deteriorated or loose.
"A" could be caused by a faulty float valve pin; faulty floats (make sure they float!); or a dirty carb.
If you buy the carb kit, you have a good chance of being able to fix these problems, depending on the condition of your carb. When I got my bike I had to buy a new carb because mine was so bad and then a carb kit too.