[Aircobra101]

so the engine runs great except for one thing
starts fine with choke, but as soon as its warm and i push in the choke, the idle stumbles
i've had to bump up the idle speed so it doesn't stall. as soon as you step on the gas, it stalls
i've checked for air leaks and played with the mixture screw, but no difference.
i suspect the idle jet is not right
the carb has been rebuilt by me
ps.
is there meant to be a rubber o-ring on the mixture screw?