[rdorman]

I have had the vent issue on side hung float bowls that even the vent 'whistles' didn't fix. Being to cheap at the time to replace bowls, floats etc I took a loop of fuel hose and connected the two vents together with a hole cut at the very top to act as the vent (cut the hole with the hose OFF the carbs and flush out the junk before putting the hose on!). Worked for me.
Rick