Does anyone know what is under the small round cover with the hose on it and two screws on the "L" carb? It's near and to the rear of where the throttle cable bracket is on the right side. I had mine blocked off, but I'm told it should be connected to a nipple in the front of the carb. Supposedly there's a diaphram in there. What's in there, what does it do and what would be the symptoms of a malfunction????