New amal premiers wont stay idling

With out reading through the entire thread was the question off proper valve adjustment mentioned? I have seen cases where the valves were adjusted too tight and as the engine warmed up it ran worst till it reached a point where it would stall and not start until it cooled down.

Since the old carbs had the same issue, I agree, check the valve clearance. Consider doing a compression and a leak down test.

Checked the valves, they were at regular commando specs, not combat specs. So I adjusted them. I found something that makes me think im screwed. I was sure the symptoms were still air leak related, so i got out the carb cleaner. When i spray in the nook directly behind were the intake manifold bolts up, the engine dies instantly. Appears to be the sign of a cracked head to me. I hope Im wrong. If I am right, this will be a lesson for me to be more patient when shopping for something I really want.

Very recently, I had the same issue which turned out to be a cracked manifold. Possibly I overtightened it and it cracked. It was pretty much invisible to the eye, but it did leak air sporadically as the bike vibrated. I actually had another manifold in my parts bin, so it only cost me my time to swap parts to get it fixed. If that turns out to be your bike's issue, it will be a lot cheaper to fix than replacing the head...

Spraying around the manifold to head junction affects idle slightly. But, when i put the nozzle deeper behind the manifold, the engine dies instantly. Seems more head than manifold to me.