One more time...I have a B20E much modded in a '70 142S...it was running on Mikuni HSR45's, but the Float bowls always weep after shutdown, winter or summer. I had a Fuelab $300.00 pressure regulator set at minimum 1.5 psi that helped, but the float bowls had a mind of their own...
A friend offered me a pair of Polished HS6's for 400.00. I thought this would be my answer once and for all...
I mounted them and and a appropriate throttle linkage on my lovely polished two stack B18B Intake manifold. I tested the butterflies for leakage... with a reverse vacuum cleaner...very minimal. I tried to fit new KD needles from VP Auto, but the shoulders stuck out 1/16, and all the stuff online says it should be flush with the piston face. So I put the older thicker needles back in.
At first the float bowls overflowed. I put in new needles and seats, and lowered the floats 1/16". Now they are fine.
Everything works as it should, one piston is slightly harder to raise than the other, but they both fall at the same pace, and return to the bridge.
The engine starts easily and races to 5K and stays there. It sounds wonderful, there's no smoke, no stumble. The butterflies are fully closed, The main jets are 12 flats from the top...the pistons are about halfway up, the float bowls are not overflowing. If I pull off the brake booster hose, it slows to 4000 and stumbles a bit, back on it goes to 5K, happily racing along. Upon shutdown it shuts off nicely, no dieseling.

Any thoughts???