tune bad spot out of GK71B

[hutchwilco]

Hi there,
I'm looking for help with eliminating some problems with my 85 GSXR400. (GK71B)
If there's a better forum more suited to my bike (twin carbs) please let me know.

I have a problem that when starting from a stop, the very first application of throttle and engaging of the clutch causes a muddy 'hole' ('flat spot' doesn't seem to do it justice) and bike seems to hesitate, until the revs hit about 3k (my tachometer starts at 3k) when it takes of like a rocket and seems to take good application of the gas throughout the range of speed and revs.

I've adjusted the pilot screws, finding too lean and too rich and found about 3 turns is best (factory settings says 2 turns).
I've also tried to adjust the floats but only ever made it run terribly so just reset to factory.
The pilot jets have been cleaned out by me, as have main jets. The needles don't appear to have wear.
As I understand it, the bike was overhauled (exact work done I don't know) prior to being stored for 8 years after which I bought it.

Does anyone have any advice for eliminating this symptom of very low rev, moving from stop to starting to roll? The 'hole' would only exist for a few yards of movement forward. The problem is disconcerting when moving in traffic and generally makes me feel unsafe and unsure I could quickly move to avoid another vehicle.

Also, it seems to get worse as it heats up which implies a richness problem but I can't seem to eliminate it by setting the pilot jet screw leaner...

Thanks for any thoughts