My 1978 Kawasaki KZ 200 with 5000 original miles on it, makes a loud , resonant honk or moan for a second or so after the engine initially fires when cold, as if it is releasing pressure somewhere ?

 

As far as I know, there are two places which release pressure and that is the combustion chamber and the crankcase as the piston alternately cycles up and down.

You might try this experiment. Using the kick starter, slowly rotate the crankshaft with the ignition off to see if you can replacate the sound. If you can, listen where its coming from. Check to see if your crankcase ventilation hose is partially blocked. If it's the combustion chamber, you should hear sound coming from the carb so see if you can remove the intake to hear it better.

I don't own one, but KZ's are cool little transportation bikes.

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I will give that a go thanks .

 

Yes, if yours has the air suction valves , inspect. Basically reed valves that get weak and start to Flutter
I am not sure on your model, but the 1983 550 had them. It was a US emissions thing