Help with rebuild

[nuttyprof1]

I just gone done putting together my mongrel GSXR 750/1100 with 1986 frame and engine. The engine (which is basically that of the 1200 Bandit, as you know) was all in pieces when I bought it, and I am pretty good at rebuilding, but lousy at making it work right. Right now the engine starts with at least 3/4 choke, but will not run at all if the choke is pushed in, even when it warms up a bit. Also, when I open the gas, instead of revving, it kinds of dies. At first it backfired a bit, but I tightened the exhaust studs and that went almost entirely away. The valves were adjusted to correct values. The head is ported and there are some mods, but the carbs are Keirin CV carbs. My guess is that I need to pull the carbs again and clean them more thoroughly. I kind of cleaned them, but I wanted to put everything together to see if it worked. The idle mixture screws are out 3.75 turns, and another guess is that I also need to take them out a bit more. Any other guesses as to what I should look at or fix?
Thanks  

[Red01]

What kind of mods besides the headwork?
Which Keihin carbs are on the bike?
(B12's came with CV Mikunis.)

Anyway, sounds to me if it only runs on the choke when warm your mixture is off to the lean side and that's why you have help it out with the choke/enrichening circuit. Another possibility is the CV's vacuum diaphragm(s) are leaking (pinched from assembly error or cracked from age), which could cause the stubling when you try to accelerate... as well as give you a full-time vacuum leak, which would also cause a lean condition.

[nuttyprof1]

Just to let you know: I took off the carb, gave them a thorough cleaning, inspected the diaphragm, etc., put the carbs back and now it runs without choke and responds to the throttle, so things are looking up.

[Red01]