This is probably not new to some, but it was quite a discovery for me.
I had my carb disassembled for a rebuild, and I couldn't figure out how to get at the three small orifices under the butterfly valve to clean them.
Well, I looked and looked and it seemed the only way to get to them was to pull a core plug, but I couldn't find the post I had once read describing the best way to do this, so I sprayed some carb cleaner on the three orifices and let the cleaner pool, and watched for where the cleaner drained out.
The cleaner drained out a small hole in the bottom of the casting, so I sprayed carb cleaner in that hole, and it only came out where the low speed mixture screw went in.
So, I plugged the hole where the Low speed screw goes, and voila! At first there was only spray from the center orifice, but soon after, I got full flow from all three orifices!
I believe these orifices to be where the gas comes in for the motor to idle.
Here are some pics.
The above pic is of the offending orifices.
The above pic is of the straw from the carb cleaner inserted into the hole, and the Low speed screw hole plugged.
And the above is the result of plugging the hole and spraying the cleaner.
The flow actually looks like little geysers when going full bore with the cleaner, but I was trying to spray the cleaner, plug the hole, and take a picture at the same time, so It doesn't really do justice to the full effect.
Hope this helps somebody.