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???

Your weeping Mikuni cards, they are supposed to be gravity fed on a chopper, so..... Get a chopper fuel tank & duct tape it to the roof, I thought about bonnet mounted chopper gas tank, but I think the cops might frown on that...

The Serious Answer:
• You need to bleed the pressure out after you turn it off.
• Some short bits of 1/4" & 5/16" pipe, preferably cad plated like Volvo use.
• 1st, a piece of 5/16", 2" long, half way along, drill a small hole, braze or silver solder a 1" long piece of 1/4" or 5/16" pipe to it, stick that on the hose feeding your fuel pump.
• 2nd, a piece of 1/4" and/or 5/16" pipe & make a second T-piece out of & stick that between your regulator & carburettors, the hole you drill in the side of that should be as small as possible.
• Connect the bleed T-piece & the pump pick up T-piece together with the appropriate sized hose.

This will solve the Mikuni problem.

The SU's: Take them off & see if the throttle blades are the right way around & you can't see daylight around them when you hold the piston up, that's the only real source of air/fuel mixture that can make it idle fast smoothly. Other sources of air after that will make it pop & backfire. Some wick-in Loctite should be applied to the throttle blade screws AFTER you are sure they are Hunky Dory/Ridgee Didge!

Cheers,
Paul.

Update...

I've now blocked off the suction tube I was using for the Brake Booster with a tight fitting Rubber Tube Cap...no change ...easy start and race to 5000...

Damper oil?
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com