Overall, a very nice effort. I do have some constructive criticism. (Isn't that a surprise!)
1 - I agree with a previous post that your "idle" is far too high. Sounds more to me like it's at 4000 RPM.
What this means is that the slides are farther open than they should be for the final sync adjust, and this makes the critical fine adjustment impossible.
The vacuum reading is most sensitive when the slides are almost closed, which coincidentally is the lowest idle speed. I'll use the lowest idle speed (tiniest slide opening) I can get, even if I need to make two or three passes at adjustment, just to get it that low.
2 - When you have the proper low idle, each intake pulse can be seen on those gauges, which makes them swing wildly. The Gauge kit should have a damper valve for each vacuum connection to limit the gauge needle swings. On mine, I set those dampers to about a "one tick" scale reading excursion. This way I can visualize the center of the swing as a reference to compare to other gauges. So, you need to add damper installation and adjustment to that video.
3- You trust your gauge needle's accuracy too much. You should connect all four gauges to a vacuum source, and compare the readings of the gauges to each other. When brand new, they should all be reading the same excursion, if adjusted correctly. Time and knocking the gauges around can change them. They can also develop leaks in the tubes and the internal components that can change the needle deflection. So checking the gauges for correct comparative readings is step one of using gauges.
4 - They style carb you've picked allows the individual slide adjustments to be skewed so the slides CAN'T be lowered far enough for correct idle speed. This will often make the main idle knob useless for setting the correct low idle speed. (This may explain why your current idle is so high.)
Some other carb types only allow three of the four carb to have an adjustment CB550K PD carb styles, for example.
So, I have to disagree with your adjustment recommendation of adjusting all the slide travel adjusters. If you have a decent enough idle, you pick one carb to use as a reference carb and adjust all the others to that single carb that has NOT been adjusted and is known to achieve the correct idle speed setting.
5 - Another important missed item for instruction, is that prior to the carb sync, all the standard tuneup items should be addressed first.
Valve clearances, cam chain tension, spark plug gap/cleaning, point gap, ignition timing, air filter cleaning/replacement, and all the air bleed screw settings should be checked. (I would also >like< to see (or have a mention about) a compression check showing that all cylinders have the capability of running at the same strength. But, that is probably not essential for a basic instruction.) In essence, you want to adjust the carb sync last, so that the engine is assured to be capable of firing on all cylinders with equal strength and equal vacuum draw.
6 - I just noticed you called the leftmost cylinder number 4. The leftmost cylinder is number 1 in all the shop manuals.
7 - You completely overlooked the adjustment lock down nuts, which must be tight after adjustment and STILL have the proper, equal reading on all the gauges after lock down. Without those lock down nuts tight, the carbs won't stay synced for very long.
I hope you will make these corrections to the youtube post.
