While I was cleaning the venturi clusters, I noticed that one of the emulsion tubes of the primary cluster was cracked. I read up on this a bit and found it to be a fairly common problem. Some guys leave it alone, others solder the crack. I decided to try to remake the tube. The tubes are .2175" inches outside diameter with a flare on the end of .279". I found that 7/32" brass tube from the hobby shop is only 125 thousandths too large and 9/32" tube is 225 thousandths too large. After a few failures, I figured out how to accurately solder the large tube over the small tube to kind of simulate a properly expanded flare. The emulsion holes in the tubes are right at .040" and I had some .040 drill bits handy (1mm) so I laid a piece of transparent tape over the holes of a good tube and transferred them to the fabricated tube. Finally, I chucked up the tube into my drill press and sanded the "flared" end down to .279". I then pressed the tube into the venturi cluster making sure to aim the holes in the same direction as the originals were. By the way, I did try to find an old carb, venturi cluster, or even replacement tubes but came up empty (for less than $25). Otherwise, I wouldn't have bothered.