This is what "mechanics" do with your carbs. This is wrong but it does work and it helps their simple brains by simplifying things. Another reson they do it is because the idle circuit cut off valve is broken. They could snip the plunger off and set them normally and sometimes that has been done so pulling the wire off doesn't do anything - unscrew it and have a look if that happens. Back to what the mechs do: They screw the idle speed screw right in then set the idle speed with the throttle stops and mixtures with the screws on each carb like "proper" carbs. That's fine but why do this when you can balance the carbs once and then set the speed without disturbing the balance whenever you want using the idle circuit speed screw? I wouldn't be surprised to find yours like this.
LHS carb view from LHS RHS carb viewed from above LHS carb view from above View of whole engine LHS carb view from rhs/inside rhs carb view from lhs/inside Does that show all?
You are going to have to ignore my waffling about idle circuits. Your carbs don't have that, they are simple earlier (i'd guess) ones. Therefore you and your chosen ones will have been doing the right things I'd guess as they're very basic.
i di i didnt want to presume you were wrong. Not a lot of people have these carbs as far as i have seen so far.
Do check the cut-off valves are working though and for me, unscrew one and see if it has a moving plunger on the end or a jet.
That has idle jet built in. Check it's not blocked on the side you can't adjust and check it works too. If not I have some, one is bound to work. It should click with ignition on when you unlug/plug in it's lead.
I still think it's balance though - when you carbs are even a bit out, you won't be able to adjust the mixture on the lazy side as it's not doing enough to change the engine note.
Back to the carbs - the plastic knobs at the bottom are where the mixture screws are in the later ones so I'd say they are them. So the big ones are what - they would be idle speed on a single carb. I would try setting the throttle stops so they are just touching then minor adjustments to balance with the meter and if it's not running fast enough, unscrew those big screws to speed it up. You might have to go round a few times.
To keep it running you will have to do above on the hoof - i.e.if you reduce tickover with a throttle stop, try speeding up with the big screw. If it works carry on.
