Mikuni 34 idle jet, yes, that old chestnut.

The bike has always started on choke since installation . However, others have said to turn the choke off after a few seconds. If I do this the engine dies under about 2000 . If the choke is off it runs badly with the occasional backfires until warmed up . All perfect when warm ! I run a 35 pilot jet and I'm going to try 37.5. Anyone had this problem ? Roy. Ps it takes about 2 mins to tick over without choke .

If it runs good once it's warm leave it alone

How many turns out do you have the idle air bleed screw for maximum revs when warm?
I have identical setup as you and I use choke to start and immediately turn off the choke.
After about 20m seconds it will idle at about 900 rpm (with trispark that I think really improved cold idle).
Drives fine after 20 seconds of letting it warm up a bit
When warm idles about 1200 rpm.
I wonder whether your carb needs a cleaning, especially those two little holes the idle mixture comes out of downstream of the main jet.
Dennis

Mine does the same if I turn the choke off before the bike is warm. As others have said: leave it alone.

Yes.
When you start the bike turn in the idle screw raising the slide. About 2 or 3 turns of the wrist. Then the choke which you turn off immediately when it fires. If it really cold then leave the choke on as little as possible

I normally start the motor with the enricheners with the throttles closed and let it idle until it slows slightly, then take the enrichers off. When the motor is cold, it needs richer mixture - you need to wait. The slow running cycle in the carbs, probably works with the cut away until you have about one-third throttle. A bigger idle jet might slow the bike slightly, when it is ridden away from a stand-still.
Richer mixture than the optimum does not give better performance, even though more fuel contains more energy. Best performance is as lean as possible without burning valves or pistons. If your motor misses - stop and fix it.

I had exactly the same problem. When I changed from 30 to 35 everything was fine. I would recommend you just try the 37.5 nozzle and see what happens...

It's appart for cleaning and inspection at present so I will try the 37.5. Thanks, might help ? Roy.