>Are you saying to lower it that low just to do the sync or for good and why?
Unfortunately, you need to lower it that much to keep the digital ignitio from advancing and causing it to pick up idle speed.
A stock pilot system calibration is going to be lean at idle even if you put a larger pilot fuel jet in. There are two pilot air bleeds, one in the carb mouth (0.7mm I think) and one under the diaphragm, a 1.4mm.
The one under the diaphragm is shut off by the 'coast down' valve (the diaphragm on the side of the carb) at high vacuum so the pilot circuit gets a lot richer on over-run. Unless they do that it will insist on not idling down.
In normal operating mode like idle, the two air bleeds are vacuum breaks meaning that the idle fuel jet feels little vacuum. The off idle ports (on the airbox side of the butterfly) are also vacuum breaks in that mode. That is why putting a larger idle fuel jet in doesn't really make the idle a whole lot more stabile. It still has a limited vacuum in that system.
If you change the top idle air bleed to a 1.2mm Mikuni air bleed, it will make the idle a lot more stabile and allow a bit more fuel to be adjusted at idle.
The stock system is quite lean at idle and removing the air box lid or un-restricting the air box in any way aggravates that situation.
When an engine idles really lean (and this holds only with a carburetter) the hotter it gets,the richer it runs. The fuel is better vaporized, so the same amount of fuel causes richer combustion.
It's the same effect that requires a choke. If you start a cold engine the A/F meter will indicate lean until the engine starts to build temp and then it gets rich.
Anyway, as the mixture goes from way lean toward best power mixture, the engine responds by idling higher. When it hits that 1500 RPM point the ignition starts to advance and first thing you know it's idling at 3000.
By getting a mixture closer to best power mixture at idle, the tendency of the engine to pick up speed is greatly reduced. It hates way lean, so almost rich enough gets you a good idle speed and it doesn't pick up quite so much as it gets hot.
Another problem with that engine is that it idles at 6 degrees BTC and the vacuum is real weak. When you have to retard it a couple for a high compression kit the idle gets even softer and the vacuum goes down more.
The reason the vacuum goes down is that, instead of the engine making the power to idle from more ignition advance, you need to open the throttle to make the power to overcome the friction. Opening the throttle drops the vacuum.
With a 944 HC engine you might even have to open the throttle at idle until it runs off the first off-idle hole. In tha case you won't be able to adjust the idle mixture through the full range because you only have cojntrol over the idle port.
There isn't much you can do beyond jetting and constant adjustment, unless you by the Silent Hektik ignition and add some timing at idle.
Or, maybe I'm wrong?
Doug