part to mid throttle missing? problem

[weighates]

I own a 1991 GSX750F. It is a absolutly beautiful bike. Everyone that has seen it thinks its a 2000 or later because it is flawless. She has 11,380 miles on her. Now on to the problem. It idles between 1500 and 2500 rpm when warm. It does go up and down between 1500 and 2000 usually. This isnt a big problem for me as I like the high idle. At part throttle it seems almost like it maybe running on 3 cylinders. its kinda surges abit like the 4th cylinder is kicking in occasionally. At mid throttle or past 4th cylinder kicks in and its goes great at higher rpms like say 6k on. Below 6k ish it sorta stumbles abit. It also runs poorly when cold. I pulled the plugs 2, 3, and 4 look great. 1 looks really black. So what do you guys think is the likley culprit here. I am definatley thinking of doing something to carb #1 but I am really unsure of what to do. Any thoughts?

Thanks a ton guys,

Chris

PS - Ill post pics of my bike tomorrow if you guys want. I have personally never seen a bike this old in this kind of visual shape. Its all stock but looks great.

[akarob]

Clean your carbs and resync them - particularly the emulsion tubes. Poke the holes out with a .020 wire and it'll be good as new.

[kevin2502000]

Replace ALL you rubber orings, 20 years has dried them out and created air leaks.