I'm not aware of any diaphragms that will last as long as leather. However there was a fellow on eBay selling an orange diaphragm touted to be very ethanol resistant. His name is Burchfield...seems like a good guy, but today is not selling those. Just the black rubber ones. I first bought one of these 3 or 4 years ago and was testing it...when I sold the carburetor it was installed in. So I bought more of them and have been using them since. The one I have in my YF3211S is currently going into the 3rd year of testing with no problems. And I should tell you I've let the carburetor dry completely out 4 or 5 times since I started testing it. The problem with the black rubber diaphragms is they last ok as long as you keep them wet with fuel. If you let them dry out, then they deteriorate much faster...almost instantly it seems in some cases. I've discussed this with the other Jon, and the problem is lack of demand/cost. There are materials out there which would be ethanol proof, however you'd have to have somebody tool up to make those...and there aren't enough YF carburetors still in use to make that an attractive project.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end