ok, i was on here a while ago with essentially the same problem, maybe ill get a fresh perspective on it.

I have an 82 kz550 that i have pulled, cleaned and then rebuilt the carbs, they're balanced out (far as i can tell.)
I also put caps on the nipples on the center two going into he head that are not connected to the air hose system, that helped it start. I also took out condenser plate, took it apart and scratched the corrosion off and that too helped, but now im in the same place. I turn it on, hold clutch and starter and i may be holding it for 2 minutes and no start. it may chug (yes gas is on, its on prime, and i watch the gas flow in transparent line) if i put the slightest hint of a choke on, i get no more chug and it only has the starter running. sometimes the slightest bit of choke helps but any more than a hint and i just get starter running. same if i put the throttle on at all when starting. sometimes after the 2 minutes of holding the starter i let go and it still puffs a bit, usually it takes a few of these for the puffing to keep going and it may slowly get up to idle. when it gets running i can rev and put on choke and do whatever i want, but when it's cold, it doesn't want to start. Ive pulled plugs and they were a little black so i adjusted the mix for more air (carbs still set at about 2 to 2 1/2 turns) and the problem remains, if anything it got worse. I rebuilt the carbs using stock kits and everything got replaced but the needles, i couldnt get them out or i'd of chewed up some screws getting to them but all jets and the rest got replaced. And it runs when it starts, so something tells me the needles are not the problem. starting fluid makes it rev up, like it's supposed to. when it gets warm, it will restart fine, even if its a little warm i get some of the cold start problem. so the colder the bike gets, the harder it is to start, new air filter. doesn't seem to have a problem drawing fuel or air, I pulled a spark plug, and when holding it, it shocks me pretty good (same as another of my running bikes...yeah im weird, i compare shocks from different bikes).
Im wondering if voltage regulator is flipping out since i seem to be able to melt fuses when i get it on and rev the hell out of it, and if that is going bad, would that contribute to the cold start problem?

I have a clutch slip problem i think as well. I get on and have to convince it down the drive way, off the clutch and rev the engine it will die. ive has times where im at 6500 rpm, easing off the clutch, it will pull me a little then it will die. I replaced friction plates, springs and oil, thinking next is steel rings to help. sometimes i have to power walk the bike for the momentumfor the clutch to engage and not kill the bike, interestingly enough i can let the bike idle or rev it and get it nice and hot and i still have the cluth problem until i get going, after a bit of shifting it wrks like its supposed to.

all in all this bike has problems when it's cold for some reason. if anyone can help, i greatly appreciate it.
thanks i advance.

p.s. i was thingking about it, and the air piston and hose system. A while ago i pulled the piston and doused it with wd40 and a bunch of black junk ran out, i put it back and thought nothing of it, im wondering if the black stuff could of been grease lubricating the piston and without it, now piston doesnt want to operate? hence no proper air movement until i get a little heat in the air from running the starter so much? or maybe its a vacuum leak being 28 year old vacuum hoses maybe not sealed like they're supposed to? a little heat on the metal, metal expands and helps the seal? or am i just over analyzing a potentially stupid idea?
thanks again

 

The KZ manual has a great troubleshooting guide. Shows you how to inspect the ignition, timing, capacitor, rectifier, etc. Good stuff. What fuel level did you set your floats at? Replace the float valve needles on a carb rebuild since they tend to get a groove worn into them so they tend to seep gas while sitting. Good luck with your troubleshoot and welcome to KF.

 

I searched the manuals and got very little describing my particular problem. So I don't know if it's one problem or many problems. It reads like this "starter runs but bike won't start. could be weak battery, or no fuel to engine or air filter clogged or spark plugs fouled or... etc." also, i couldnt find a particular of "starter runs and engine chugs" for a header.
The fuel valves were replaced on rebuild, I thought they were sticking too due to a small fuel leak so i tore them apart, cleaned them again, also bent the floats to A. make them even and B lower the fuel level, I set it close to where the book showed, it didnt give exact measurements just showed about where level sits in bowl so i tried to match. yes no more fuel leak, but still have problem.
I got new vacuum hose the other day so i'm going to replace the old and see what happens. i pulled the plugs and they're kinda black so im thinking it's air starved since i cleaned and adjusted the carbs to an inch of their life, and seeing as vacuum hose is cheap, ill start with the cheap parts first, lol.

and thanks, I like the community we have here. Much nicer folks than the shops around who won't barely talk to me because i have old steel.