wont run

ok the bike 83 KZ750 L3 now the back round this bike was in boxes i have put it together cleaned carbs 8 times lol lined the tank new air filter bike is stock i had bin riding the bike before i got the air filter and it worked ok put the air filter in adjusted carbs as best as i could by ear i know not good enough noe when i ride for about 20 min i cant keep the bike running

See if it will run longer with the gas cap unlatched. I,m thinking maybe the tank vent is not venting properly.

Good compression? Should have 130 PSI all four cylinders minimum. Spark? Should be a hot blue spark and "Snap" when it fires.

Fuel delivery o.k.? not obstructed by restrictive fuel filter(s).Carb float levels been checked?
Valve clearances been checked lately?

Sparkplug caps and wires been replaced? They age and fail over time.Sparkplugs properly gapped?(.028 to.032)is the range. Correct sparkplugs?

Hi there krazinite2003,
Synching the carbs by ear does not work even for the experts and is apt to do more harm than good. If they are seriously out of whack the bike will want to die after 20 minutes or so. I bought a Morgan Carbtune and like it and if you do a search here you will find many posts from people who built their own carb synch tools.
Are the carbs Mikunis ? Search also here for "bench synch" which would be a good starting point for a full and proper synch using vacuum gauges.

Good luck