And so it begins - GT250 carb advice please

[Bikenbass]

GT250 A.
Choke lever level or pointed down for normal running please?

This is a weird one;
Both air screws are wound out 6 or 7 turns from fully home. The engine runs, ticks over at 1200 but slowly dies. If I put the choke lever into the down position, the engine sounds crisp but both exhausts smoke and it dies after ticking over at close on 2000 rpm.
If I wind the air screws in to 1 1/2 - 1 3/4 turns from fully home, the engine screams up to the red line and I have to kill the ignition to save damage.
Anyone had this happen, any solution?
Right cylinder and exhaust feel hotter than the left.
Both carbs are marked Z 77
Thanks in anticipation.

[Kettletimes3]

Are you using the choke to start,that’s lever down.
When engine warms up and and choke knocked off will engine continue to run or does it stall,
If it stalls it sounds like you have block pilot jets.

[Bikenbass]

Are you using the choke to start,that’s lever down.
When engine warms up and and choke knocked off will engine continue to run or does it stall,
If it stalls it sounds like you have block pilot jets.

It starts on choke and sounds nice and crisp. With the choke off, it's not very responsive to the throttle and gradually dies.
I think a total strip down of the carbs to investigate is needed along with a thorough cleaning.
Thanks for your reply.