Carb "O" Rings..........

Yeah, that's probably as good as the other way, which would be using one of those fuel stabilizers, but even with those, 2 years seems like it's pushing it.

If you buy a carb rebuild kit, you get the the stuff for each carb, but nothing for the fuel and vapor rail, which need to be replaced, too.

The fuel system o-rings are almost certainly made from Buna-N or Nitrile rubber, which has a 10 year shelf life, and probably a 15 to 20 year service life. So they're going to have to be replaced at some point soon. Nitrile is the material used for gasoline, oil, diesel fuel, in short, any hydrocarbon or petro-chemical. But not brake fluid, alcohol, water, etc. There is one compound of Viton which is pretty good for gas and alcohol mix like we use here in Calif, but Nitrile is the standard.

In my case, the 1997 vintage o-rings were rock hard when I pulled the carbs apart, and had been seeping, for the record. I was thinking like you that they'd swell back up again, but no bueno.

So I measured the fuel and vapor rail o-ring grooves, and having designed things that use o-rings in many various applications, I figured out what was needed. I ordered them from this place on line- and they were way cheaper than the Honda units . I'll try to post a photo of the receipt showing the sizes, prices and supplier. No guarantees on the posting part on the first try.
Check out how much o-rings really cost! The shipping was just about as much as the o-rings, and I bought way more than needed.

They worked perfect, assembled easy and were nice and tight, and don't leak.

My insert image button ain't inserting too well- here's the sizes:

Vapor rail and fuel rail

N1.30 x 008 - 1.3mm cross section x 8mm ID, Nitrile (12 cents each)
N1.78 x 007.94 - 1.78mm x 7.94mm ID, Nitrile (20 cents each)

from :

The O-ring Store
Lewiston, ID
203 413-6377

also online