I had a missing and a damaged vent tube on a 4100 carburetor I bought. I made replacements using brass tubing available at hobby shops where it's cheap, like under $2.00 a 12 inch long tube. I assume e-bay has it, probably Amazon too, but in bulk quantities. A Dremmel tool with a cutting disc was used to cut the length and make the slot. Set the slotted end in the vent hole in the carburetor and with a piece of wood over the end, tap gently it to get it in.
From what I've been told, the tubes are available but without the cut slot, are difficult to install.
Jim
