Running on 3 cylinders

My GPZ 550 (4 cylinder ) bike is running on 3 cylinders.

I took the carburettor assembly off a while ago to clean it, because it ran very bad. Everything on the bike is standard.
I cleaned all jets with carburettor fluid and compressed air. No cracks in the diafragma. Air box is clean.
Starting the bike causes no problems. But the left cylinder is not getting warm. The spark plug gives of a mighty spark, so not an ignition problem.
The spark plug is not wet, black or anything. So it seems to me there's a fuel problem for the left cylinder. Appaerantly cyl no. 1 isn't getting any fuel.
What is your first impression what it could be ?

Sounds like inadequate carb cleaning. Did you fully disassemble all the carbs and soak all the metal parts in carb dip?

I've cleaned it, but i didn't soaked it overnight. So you could be right. Maybe it's better if i took the carbs to a guy whith an ultrasonic cleaning device.