Idle is messed up

[xxenzor]

1980 GSX400

I have changed
- All carb o rings
- Choke plunger o rings
- Throttle shaft seal,
- Intake O ring,
- Adjusted valves
- New throttle cable
- New spark plugs
- Adjusted float height
- Synced Carbs

The bike starts good and idles smooth at 500-800 and will come down after a quick throttle blip. But the bike will come down and stall after i ride it and rev it around 6k.

If i turn the idle to 1000-1100 where it’s supposed to be. as soon as i touch the throttle the bike will idle at 2000-3000 and i have to turn the idle screw down.

I have no clue what could be the issue. I’ve checked for vacuum leaks with propane, Carb cleaner and starter fluid. Nothing.

[Nessism]

Is the airbox installed?

[xxenzor]

yes. stock airbox

[Rob S.]

1980 GSX400

The bike starts good and idles smooth at 500-800.

Idles smooth at 500?!? That's odd.

[tom203]

I’d be suspicious of those new carb boot o-rings…maybe you got skinny ones

[Lorenzo]

In addition t? all the above, I would take the carbies off and check both intake and air boots; even a slight crack or slit can get air in, which Is probably the cause of your problem