TOPIC:

1978 kz650 no air box. please help! screws on carbs one and a half turns out and only benched sync. thanks

Only runs on choke. Sounds lean to me. Only runs when you choke off the air to the engine. Look for bad carb manifolds. Look for cracks and chunks missing. Have jets been changed to match lack of airbox. Try put airbox back on.

I will guess the bike sat for awhile? It sounds like the carbs need cleaning. The pilot jets are clogged.

Put some air filters on the bike and rejet appropriately. Bike is over lean because of no filters and stock jetting.

Listen to WG, he be the MAN!
The carbs on a 78 650 are not equipped with a REAL choke but an enrichment circuit that feeds more fuel to the engine while it is cold. same principal which is to enrich the mixture while cold but this doesn't restrict the air.
the pilots and needle jets may be stopped up or not but
those carbs won't run right until you put a stock air box on or some pods and jet for them no matter how clean the jets. (voice of experience)