I have a 435cc 1972 Dyane, I want to check the carb is set correctly, I have read to set the idle with the butterfly stop screw located on the rhs of the carb roughly in the middle, which I have done once the engine is up to normal operating temp. Then at the bottom of the carb at the back is a large knurled nut, I read to turn this in until the engine runs rough (almost stalls) then back off half a turn. I did all this but I can almost wind it seated and all that happens is the revs increase to a fast idle? Now I have no idea where the proper setting should be, since owned it sprays black soot over the rear wheel (side exit exhaust) and in the snow it makes the snow black so it's running rich

Ken/Sean/ anyone please help I think the carb is a 34 pics 4 or 5 I need to check for sure if you need this info

Many thanks in advance

Sounds like time for a new (reconditioned) carburettor. If the spindle or housing is worn (out) you have no hope of ever getting the adjustment right.

Does it sound like I am adjusting it correctly? It's a 34 pics 6 by the way, winding in the knurled red knob on the back just makes the tickover increase

Before attempting adjustment of a carburettor, everything else needs checking/adjusting. Compression test, valve adjustment, points and timing, air filter even breather test. If all this is OK, then carburettor is to fiddle with.
The red rear adjuster is the fuel/air (mixture) screew. The idle will respond to adjsuting the mixture screew. There is another screew (spring loaded) which will adjust the air (idle) Many a photo would be good

As requested Viking

Is there a standard setting from seated for the rear screw? , timing is ok, tappers set, not checked compression or vacuum as I don't have a tester or manometer. It's just running rich I think as snow black as is rear wheel

The idle is adjusted directly on the spindle activating the butterfly. Feel the play on the spindle. If flapping around too much, it is very hard to get a smooth idle. Too much air is sucked in distorting the idle and the fuel mixture.

Spray some carburettor cleaner around the base of the carburettor and listen for any change in idle speed. Do the same on the inlet gaskets between the mainfold and the cylinder heads, often not sealed properly also sucking in air.

If the carburettor is worn out, you can't adjust your way out of it. You may need another carburettor.

If the idle becomes too fast as you lean off the idle mixture by turning the idle mixture screw inwards, don't you just need to back off the butterfly stop screw slightly?
Note that with unleaded fuel, it's not possible to gauge whether the engine is running rich at tickover by looking at the colour of the snow where condensate from the exhaust has dripped onto it...
If the mixture was too lean because of a worn spindle, the engine would tend to falter and cut out at idle.

Also note that when you're adjusting the idle mixture screw, you need to wait about 5 to 10 seconds after turning the screw for the change to take effect because of the distance the gas has to travel from the carburettor into the engine.
If you haven't achieved a satisfactory setting after a couple of minutes of idling, rev the engine to 'clear the tubes' before carrying on.

Edit. Almost forgot, the pitch of the thread on those idle mixture screws with a plastic head is coarser than on the later version with a slotted head, so 'about' 2 turns out from fully home should be a reasonable starting point.
Bear in mind that it's very easy to damage the fine point on the idle mixture screw by winding it in too hard, which is why I usually advise not using that approach.
On these particular carburettors, as long as the original spring is present, that should minimise the chances of such damage.

ken

thanks ken, i will try again tomorrow, although as i wound in the idle mixture screw and backed off the tickover screw, it got to a point where the butterfly screw was not actually coming into contact with the carb at all (fully wound out with a visible gap between the end of the screw and the carb lobe. and the tickover was still racing. admittedly i did not rev in between. I will try two turns out from seated, and i am aware not to wind it home to hard as risk of damage to the seat.

thanks ken