Ok. I tried cupping my hand over the throat. The front carb has a lot of vacuum and sucks my hand down if I get anywhere near the throat opening. The rear carb is another story. I have to put my hand completely over the throat before it affects the idle speed at all. Having said that, I've tried the propane thing around all of the carb gaskets, connections, etc and cannot find a source of a leak. Could it be somewhere else? Intake? Head?
