I must admit that this is quite the head scratcher, particularly after yesterday with the shim experiment. A couple of things come to mind. Firs Fast Larry's Bandit FAQ:
If you look in the carb section there is a listing of potential mods, and a reference to shims that can be bough from Radio Shack (of all places!?!)
The reason for buying them there, is that apparently they are very uniform at .05 width. Here's another interesting page from a Valkyre site:
Notice what this pages says about adjustable needles in STEP 9. In addition, if you change the needle jet position with shims, you need to adjust the pilot circuit mixture.
So after refreshing my memory on this, I was reminded that the pilot or idle circuit controls the mixture of the carb to 1/4 throttle, after which the the needle jet takes over. IIRC, this is exactly the throttle position where this problem is occurring, right?
So, perhaps a set of radio shack shims (Radio Shack shim part 64-3022 or 3022A) and set of calipers (to insure that they are uniform in thickness) might be worth picking up. I don't know what thickness the shims we got yesterday are, but this is really a very fine adjustment so it probably matters.
So in summary, I'd say pick up several shim packs, then try adjusting the carb mix back down on the idle circuit to stock. Add shims and check the 1/4 throttle transition. If the bike is bogging with 3 turns out and one set of shims (of unknown thickness and uniformity), then I'm guessing it's too fat right now. Or, just order a set of adjustable jet needles so we can try different needle heights:
now this may not be the *right* needle for this exact carb, you'd have to verify the number, or find one that's identical in dimesions. OK, now for one more ref from the bandit faq:
and finally, a link on the general tuning of CV carbs:
As stupid as it may seem to have to go through all this, some times they DO get it wrong from the factory. But remember carbs *can* work just fine. Several forum members here ride Suzuki DRs, which are carbed