Suzuki GS and GSX Carb O-rings.

They don't make it easy...
Whenever a vehicle is designed, it's very important for the manufacturer to use odd sized O-rings. Forget rounded-up to the next millimetre sizes, you are guaranteed that the vital one needed will be 3.67mm in diameter and 0.89mm thick. Should you, by good luck, find an identical size, it'll probably be of the wrong material. 
And don't even get me started on the old "universal" box of O-rings you can buy! These were a great money spinner for someone, but they won't actually fit anything, and you'll be left with a full box thirty years later.

So when it's time to rebuild the carbs on your GS/GSX, it's nice to know that someone has already done the hard work, and research, for you and can supply the complete set for a great price. Without the right ones, your bike will never run properly.
Robert Barr's website http://www.cycleorings.com not only has the right parts, but also comes with tips to help you do the job. I'd already bought some of the O-rings for the GSX carbs, but the ones niggling me were the tiny ones for the mixture screws. I struggled to find the right size, so decided to buy the complete kit for US$16 delivered. Awesome service!

GSX750 - Cleaning the Carbs, Carbies or Carburettors.

Call 'em what you will...
But this is the thing, the 6Sigma jet kit was ready to be fitted; the carbs were looking a little worse for wear; they needed a damn good clean; and I bought a damn cheap ultrasonic cleaner.

That last point, and my grammar, was a problem...
Now the bike ran ok - ok it didn't idle properly (but then it was in a pretty bad state), but it gave me enough of an inkling that most of it was pretty good inside. And that's half the battle. If you have a non-runner, "do it up" and find something's not right afterwards, it can be hard to pinpoint the problem. At least now when it all goes tits up, I'll know it's probably something to do with a part I've stripped - like the carbs.

Initially, they looked like this.
Dirty on the outside and, due to an air filter that was long overdue for replacement, not too good inside either. So onto eBay for an ultrasonic cleaner.