Hi, Here's the problem, it's a 98 M900 with carbs, lately when I start the bike, after its been sitting for a day or two, I have gas dripping out of the exhaust mainfold where the muffler slips on. Its not much, maybe a couple of tablespoons full, and the bike seems to run fine. I haven't noticed any gas mixing with the oil. Is it possible that one of the carbs [I suspect the horizontal cylinder] is leaking through the intake valve and filling the cylinder?  I don't know too much about the fuel system on this bike, are there bowls in the carbs, or is there a vacuum controled petcock that's leaking?
Any insight would be appreciated.
Thanks
O

There are float bowls in the carbs that stop fuel flow.  But many things can cause these to hang open, such as some debris in the fuel or sometimes the float will just stick open.

Also, the emulsion tubes/needle jets will eventually become ovaled which allows fuel to leak past them even when the needle is seated.  This will usually cause your bike to gradually start running poorly, though.

The vacuum petcock is on there to keep the cylinder from flooding if the float hangs open.  Those very commonly fail.  It is located just under the tank hinge.  The easiest way to test the petcock and floats are to drain the float bowls.  They should quickly empty, but if they continuously drain, then you have a stuck valve and probably a failing petcock.  I would suggest putting a manual petcock on there anyway because the vacuum one is so prone to fail.

Thanks for the quick reply, I'll check out your suggestions,