A
altermad
Guest
Horrible ain't it!
I had a similar carb overflow problem (when I set the petcock to prime) before I stripped, cleaned and replaced the o-rings in the carbs. I was advised it was likely a sticky float (which turned out to be correct) Try gently tapping the underside of the #4 bowl with the plastic handle of a screw driver (when the bowl is full) to see if it stops the overflowing.
Did you replace the the Large O-rings on the carb boots that are mounted on the engine? (accessed by removing the boots) Leaking O-rings might explain the sound of air sucking that you are hearing.
Did you replace all the O-rings in the carbs itself when you cleaned them? What did you clean them with?
I replaced all rings from cycleorings.com they are great. Including the intake orings. When I opened carbs they were very very clean. You can tell they were dipped recently. I hit them with carb cleaner spray from napa (In every crack and crevis) and then put on new o rings and new bowl gaskets.
Before I took them down they did the same thing (Dripping from #4 bowl drain) but it wouldn't even run then. So I am now taking airbox off to get to carb bowl screws and I'm going to drop floats to 24mm till it stops leaking. Does this sound like a decent aproach?