81 KZ305 bogging down on light acceleration and lean surging

Bike starts and idles fine, but bogs down just off idle to 1/4 turn. Give throttle a good crank and bike accelerates fine. Also lean surge when gentle riding 35 - 55 mph.
Shimming the needle .050" helps, and shimming to .080" is almost acceptable. I'm considering shimming to .100", but would like some input from the group as to why I need to shim at all.
Carburetors, air box, exhaust is all stock. NOS Kawasaki air cleaner, Replacing needles and needle jets with genuine Keihim parts did not help. Fuel level checked with clear hose. Slides seam to raise and lower normally with carbs on bench connected to shop vac.
What am I over looking?

ive got the same issue minus the lean surging.

im all stock, 77 kz650 except ive shimmed the needle clip by .050 at position #3..

ive got no idea why its so bad off of stopped throttle

I ended up shimming needles .100" above stock. It's running great now. I found no intake air leaks. With air box, exhaust and carbs stock, I can't figure out why I had to do this. I'll just keep riding this way, as I haven't found a down side yet.

ckahleer wrote: I ended up shimming needles .100" above stock. It's running great now. I found no intake air leaks. With air box, exhaust and carbs stock, I can't figure out why I had to do this. I'll just keep riding this way, as I haven't found a down side yet.

shimming .100 above stock.. this mean .100 richer than the third clip?

The needles on my kz305 were not adjustable. I had to improvise and use shims.

ah, gotcha, a kz305, so you shimmed by a kz650 1 step richening up the mixture by raising the needle