3500 rpm stall 02 rx carb

[JACKOMO]

Not sure why but if I hold the throttle at 3500 rpm the engine will stall. If I let go of the throttle I can save it from stalling.

Here's what I've done

New plugs
Carbs cleaned including accelerator
Hs ls Needles adjusted
New fuel lines
Fresh gas
Filters cleaned including water separator

The only thing I have not done is replaced the selector
valve.

I think I will replace the selector but other then that any other ideas?

 

[Bills86e]

Might be the fuel water separator/filter cup is cross-threaded or just bad 0-ring and letting air into the supply.
Any other performance issues?