I have a 1994 Yamaha Timberwolf 250 2X4.  If I leave the gas turned to the "ON" position when not running, gas runs out the drain tube connected to the bottom of the carb??  Any idea what is causing this?  Obviously it makes the bike hard to start as even if I turn the gas to "OFF" the gas will drain the carborator dry.  It does not appear to leak while running.  HELP!!  I am guessing I have some kind of bowl or float issue.  Should I just replace the carb?  

Try tapping the bottom of the carb ,the bowel part .The float is getting stuck open .It happened to mine 250 4x4 and I tapped the bowel and it stopped .I hope this helps  

Yeah it sounds like the float is getting stuck.  There should be a little screw on the float bowl, make sure it is tight, or turn the gas off and wait for the float bowl to empty and take the screw out and check the o-ring.  If neither of those work, u will need to take the float bowl off and check the float to see if it has a hole or getting stuck.  keep us posted