Hard to start..1980 kz650

When its warm outside, It will start ok, but only with no choke. Once it fired off with no choke I could ease into the choke. It runs and drives like new after it idles for a second.

Now thats its cold outside, It might fire for a second, but thats it. I've played with choke and no choke to no avail. Whenever it finally fires I try and work the choke on and it dies.

Your either getting too much or too little fuel, or your spark is really weak.

Have you tried to clean out the carbs yet? Sounds like something in either the choke (enrichner) system, or pilot system is gummed up.
You may perhaps need to have the carbs vacuum balanced (syncronized) as well.

Pull the carbs, do 1 at a time. Remove all the rubber stuff a put it aside, and spray everything else clean with a can of carb cleaner. Use the included straw and slice 1 end of it into a narrow point. It will then fit into the jets (once removed), and you can make sure the cleaner passes thru. Hold the jet! Don't let it blow away. Blow cleaner thru all the carb passage ways, and check the openings in the carb as you do, to make sure the cleaner is passing thru.

Make sure all the float heights are the same before re-assembling.

Perform a manual bench sync.

Re-install, and pull full choke (no throttle), and hit the starter.

Good Luck! If any other info needed, it can be found in prior posts via the search function.

Check your spark by pulling a plug, attach it back to the wire, and hold the plug against the head while cranking the starter. The plug will spark, and it should be bright blue-bluish purple. Iy very yellow/dark, your ignition system is weak, or your plugs are dirty/need replacing.

Cheers!