KZ650 hard to start (after sitting)

Hi everybody,

I already introduced my self in '' new members'' section and mentioned that my first project bike has a trouble to start after few years of standing.

So, I have Kawasaki kz650 1978, made a project bike from it 4 years ago, ridden 500 kilometers and parked it in my workshop. I removed starter from that bike to save some space on battery and as long as that bike always started from one or two easy kicks I thought there is absolutely no need for a starter. So.. after build I never had a problem to start it, but during those 500km I had to replace three spark plugs ( 1 cyl, 1cyl and 3rd). My jetting is not stock, it's 17 Pilot Jet and 110-Main jet, neddle in the middle.I thought maybe mixture was too rich and it kept fouling my spark plugs. Yes, they were pretty dark, but it is possible to foul spark plug in just 100km ?? And fun fact, when those bad spark plug were making spark when removed, but cylinder didn't worked when they are installed.. So, they were failing for some reasons.. And then first winter came in!

I decided to leave it with fuel and start it occasionally.. It starter and sounded great every time I did it. Then after over half year fuel evaporated completely and it was abandoned for 6-10months or so.. And HERE IS WHERE FUN TIMES BEGAN!

I refueled it, tried to start - no luck.. I sprayed some starting fluid, then it started, after minute or two it worked very nicely. From that time, I can't start it after sitting for a while without starting fluid. But after I start it with fluid, I can turn it off immediately and it will start from first kick, whenever i want.. until it will be left again for some hours and then it will be impossible to start it.

So okay, I removed, checked and cleaned carbs, fooor ten? twenty times already? Started to play with needle height, float, jets (back to stock and etc..).. Nothing.. As I have to expect as it worked perfectly before.

Changed plugs, measured compression and its 11-12 in all cylinders, replaced and adjusted ignition points, replaced coils too, but new coils gives way weaker visual spark, so after unsuccessful test I went back to old ones..

As long as compression numbers are pretty good I'm thinking should I check my valve gaps? They have to be good enough as long as I get popper compression.

So in current situation I have :

1) OEM jetting 15/102.5 , synced, clean carb (checked every .
2) New plugs, coils, points.
3) 11-12bar compression in all cyls.

So I got this problem for last two years, and in beginning of the summer I try to find a solution. What I am missing? I believe that I'm blind and forgot something obvious.
Hope to receive some genius ideas

Have you measure the voltage at the coils, (got battery???).
A bad connection in the ignition wiring/connector/coil can effect a huge voltage drop = lean spark.
(Battery negative) to frame, engine, wiring ground negative okay???

Yes, check valve clearance. This shouldn't even be a question...

Yes, all grounds are checked ant they are good! ( I even tried to attach new one between battery and frame / engine just to be sure )

Looks like valve clearance check is waiting for me this evening.

Thanks, Tomas.

Valve clearance gap is just perfect, it remained same as I adjusted them few years ago. More idea?

When you cleaned the carbs did you make sure the small hole in the choke pick up tube was clear?

Sorry for late answer, face with very busy week at work. Yes, I checked all air/fuel passages few times, looks like everything is clear and flowing as it should. I just noticed strange thing (from first time i started it) that when I open choke, I hear pretty loud air draw sound, and looks like that I have to shut down choke very fast, after 10s of work, otherwise engine will want to shut off.. Is that sound normal for KZ650 carbs? never heard something similar.

Check the choke liftets are tight and have a good gasket seal to the carb body