hmm, thinking basics here. Make sure carbs are clear, all rubbers are clean and no leaks, and a synch with fresh fuel. Oh, I'd prolly change the plugs during this as well. Get a baseline or fresh start as you will.

edit: If the fuel pump is of concern, then test it.

 

also make sure you check the vent on the gas cap.some gaskets are bad and the tank will build up vacumn.

 

Nothing but frustration.....
I changed all the fuel lines. Cleaned the petcock. Changed the fuel filters. Cleaned the carbs, cleaned the spark plugs (which may need to be replaced.) New gas, and everything I cna think of but the damn thing likes the same. Idles fine. But when I accelerate it tries to cut out. What the hell? I researched a little and found out that the bike doesn't come with a fuel pump origianlly.
Could it be the valves? How can I tell?
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I did not see a fuel pump on the 76 kz900.
Did you synchrinize the carbs yet? At what rpm is it cutting out?

 

I'm not sure how to sync the carbs...I'm still pretty new to this game. I'm learning as I go. There is no RPM guage. I have the original one, but took it off because the bracket was broken. This is a bobber style bike. I guess I could plug the guage back in just to get a reading. But the bike acts like it does it say around 2500 to 3500 RPM's (that's just guessing idle is from 1000 to 1200 RPM's) like it was before.
Now, I can ride the bike. It just have to tweak the choke to get it up to speed. Once I'm going I can leave the choke alone.
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Once you know that the synch is good, then you can play with jetting, needles, etc.

 

did you cleen your piolet jets and the idle circuts atfer cleening did you blow air through the the passages