I'm trying to start my 850 after 12 years in the basement.
I took the carbs apart, they looked good, I cleaned them anyway
put it all back together. I've got good spark and gas is getting into the cylinders, fresh gas, good compression.

The bike will run momentarily after I tickle the carbs, then dies.
The choke is on full, fuel taps open, throttle closed.
It revved once when I opened the throttle right after I kicked and it caught. It sounds like it wants to run.

What am I missing here?

Thanks for the help

Sounds just like my '72 combat when I first got it. The problem was solved by clearing the idle mixture orifice. This can be done without taking the carbs off by removing the air mixture screw and gently fishing through a guitar string. Be careful not to enlarge the orifice with your wire just gently clear any debris. I was amazed by a one kick instant start after this procedure but found they soon clogged again and bit the bullet and pulled the carbs off for a full cleaning. No problems since. If you just finished cleaning your carbs then a little attention to the idle orifice may be all you need. Good luck.

I heartily concur, it is all about cleaning the idle passages. It require a chemical soaking of real carb cleaner not just a spray job. often the blocking plug needs to be removed and the passage scraped with the correct # drill bit then a good back blow with a needle air blow tip.