When I first got my cb750, 3 of the 4 carbs were constantly leaking gas from the overflow tubes even after I adjusted all the float heights. When I examined the little brass standpipes in strong sunlight, I saw that they were split almost from bottom to top...undoubtedly from some water being in them over a cold winter. I tried to pull them out of the bowls, but saw that I was going to damage them. I went to the local Hobby Lobby and purchased a package of brass tubing for a few dollars. The size is critical. I bought 5/32 in. OD. I cut pieces about 1 mm less than the exposed part of the standpipe in each bowl. I made sure there was no burr on the inside of the cut pieces and then tapped them down over the standpipes. It got a little tricky towards the very end because they fit so tightly. After the first one, I thought about cutting them a little longer and then trimming them later. I don't think it makes much difference as long as you don't end up with something longer than the original. It is very important, however, that you have a nice square cut on the bottom end and you drive it down all the way. In my case, they fit so tightly that I never had to do another thing. I never had another drop leak out and I believe they will last the life of the bike...especially if I make sure to drain all the gas out of the carbs when freezing weather comes in the winter. Really an easy fix.
