When it finally settled down, it was OK, but really sounded "funny". Lots of popping back through the carbs, but I had just adjusted the valves, so they were not suspected. Connected the mercury sticks to sync the carbs. They weren't too far off, thanks to a decent bench sync, but, in the process of tweaking the center adjuster, I, of course, turned the screw the wrong way, making the adjustment WAY OFF. The difference went from about 3cm to about 8cm, but the bike got smoother.
Lots of smoke building up in the garage from all the cleaner that I had used on the engine to get the gunk off, so I ventilated the garage and went to bed.
Tonight I went back out for another attempt. Played some more with the sync adjustments, then decided to play with the idle mixture screws, too. I had preset them all to 2.5 turns after the rebuild, just like most of us suggest to all the newbies, "set them between 2 and 3 full turns out from lightly seated". Well, let's just say that it wasn't enough. After playing with all the mixture screws (keep in mind these are CV carbs) for a while and finding the leanest setting before the idle speed dropped, I finally stopped the engine to record the settings.
Imagine my amusement to see what the final settings were:
Carb 1: 3 3/8 turns
Carb 2: 3 turns
Carb 3: 3 turns
Carb 4: 2 turns
Why the differences? I don't know, but that's where it likes to idle well. We'll see how it does on the road when I get the front brakes working properly.
The point of this novel is the importance of the idle mixture adjustment screw settings. While we suggest setting them to 2 or 3 turns after a rebuild, keep in mind that this is only a starting point. You WILL have to tweak them from there. I am going to change my recommendations in the future to say "3 full turns", because it's easier go get it running if it's a little rich, and you can lean it out later. AND, ... also keep in mind that they won't necessarily end up the same number of turns.
Oh, after dialing in the mixtures, I went back and tweaked the sync screws.
The mercury levels are all lined up now and the engine runs smoooooth.
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