Hi All,
I have edited this first post several times so the responses will seem a little strange. This is to avoid having to go through a list of posts and corrections to find the real information. There is some interesting posts on the net about these o-rings and especially the effect the air screw o-ring has on low speed running. See post #37 at
http://www.gixxer.com/forums/showthread.php?p=3035021
I did not even ride my own 3TJ1. Looked at the colour of the exhaust, started it, pulled tank to reveal fuel leaks all over the place and rusty tank. Stripped the carbs to reveal that all the o-rings were rotten.

A cross-reference is available at http://www.allensperformance.co.uk/ Even if you avoid genuine and buy Mikuni parts you should save a heap of money. Table is shown below. This should suit all Mikuni BDST carburetors.
Of course the table shown at Sudco doesn't match.
http://www.sudco.com/carharori.html

These two are for fuel and breather banjos
822-14147-00-00 (36Y-14147-00-00) x 12 =
3LK-14147-00-00 x 4 =

My original assumptions about JIS were mostly wrong. As I mentioned in another post if I can get my own float bowl o-rings done then I might see if I can source these in bulk quantities to put kits together. In Viton of course.
Some of these sizes are specials but there are O-rings that are close enough to be acceptable.

FUEL TAP - Just based on what seems a good fit.
large one AS-125
small one AS-13. (AS is American Standard)

cheers
Blair

it would be better having the dimensions of the O-Rings to find out the source.
For material NBR should be up to the job.

Thanks for the reply. I live in Thailand and a lot of the fuel is gasahol, so I will be using Viton to be on the safe side. The parts books do not list sizes and that is what my question is asking for. I do not understand what you mean by source. JIS is Japanese Industrial Standard, sorry if that wasn't clear.

I think what he's saying is basically strip a carb and measure what's there. As you say O rings should be cheap oce you know what you're buying

Thanks Evil! You are like a translator changing my mumblings into something that is comprehensible.
I have nearly got them all done. Just waiting to sort out the air mixture screw o-ring. It is going to cost about four dollars for all the o-rings for the 4 carbs. A bit better than the $4 for one that the parts companies want.

By the way I did the fuel tap also.
These are not JIS. Maybe the fuel taps were made by someone else. Anyway I am just replacing the large one with an AS-125 and the small one is an AS-13. (AS is American Standard)
I have not assembled the tank yet as I have to derust it first. I will let you know if it works out ok.

Just a note to say that I updated the first post. A work in progress.
Please feel free to contribute if you get a better match than me.
cheers

Another note to say I updated the first post. It now has sizes and Mikuni part numbers.