I have a 2005 Yamaha v Star 1100 with freshly rebuilt carbs reassembled synced and installed engine will start but dies as soon as you let off the throttle will not hold an idle what are possible causes?

I would pull them back apart and double check making sure you use the wire from a bread tie to clean the jets. Do a bench sync and reinstall. set the idle to 950-1050, sync and then do a lean drop and resync maintaining the idle at 950-1050.

turn up your idle???