Choke turned off turns to lurching and dying

I recently finished a top end rebuild which included a carb rebuild. I bench synced them and turned all of the vacuum screws 3 turns out (they were completely screwed up before the rebuild, so I didn't have anything to work off of). I started the bike with the choke on and it ran very very weakly. I hopped on and turned the choke off and the bike started to lurch (similar to popping the clutch with no throttle), then died.

While it was running, it would shoot out big blue sparks from the pipes (unspent fuel charges?).

I don't own a vacuum syncronizer, so I'm wondering if I should get one and if a sync would solve this issue. 1982 GPz 750, stock.

Could be the cam chain is off by one . Just a thought

Double check your cam timing and if it is correct, your carbs are still dirty and clogged.

What baldy said ^^^^.

It it still does it then yes the carb is too lean and needs the choke to help it out.

The GPz models used the Mikuni carbs, which required a complete carb rebuild, not jut spraying with carb cleaner. New o-rings also. PITA, but they work well in the end.