These were “leaned out” a little stock, weren’t they?
No, they weren't. They were tuned precisely for the engine's needs using stock components and not laying a soot coating inside the exhaust system. If you make alterations to the intake and exhaust components without telling the carbs to alter their output, and guess what, they don't provide proper fuel mixtures. Is that really a surprise?
Also, the screw that I’ve indicated in the other photo DOES control the accelerator mix, right?
Nope, it doesn't. It controls the mixture ratio at idle. Which is tuned to ideal mixture for idle operation (Max idle speed increase).
The idle mixture isn't enough to overcome the loss of fuel jet suction when you lift the mechanical slides. It would naturally stumble unless you add some fuel for the air inrush. That's where the accelerator pump comes to bear. It shoots raw gas into the carb throat as there is an inrush of fresh air. Viola! No more stumble off idle.
You will need to pay attention to that accelerator pump. It's really a useful device on these carbs. Just needs attention if it's been neglected.
It's a diaphragm at the bottom of float bowl two. Is also has two check valves to control fluid direction. They need to pass fuel in only one direction. I've always gotten them to work right with lots of carb cleaner flushing. Never had to dismantle those. The diaphragm has two holes in the surrounding "gasket", that must be widened to the same diameter as the holes they seal.
There are also inline restrictors on the tubing the links the carbs. These are important to make each carb position squirt the same amount.
Finally the posts at the cab entrances must have clear exits. It took me three tries to fully understand how to make the pump system work properly, but once that was sorted, wow, what a difference. The IMS can be set for minimum delivery, yet anytime you twist the throttle, instant power.
Watch out for replacement diaphragm parts. Some had a rod that was too short. So, compare its length with the old one if you believe it is original.
Cheers,
