Peter, you're a very thorough individual and the video segments you produce are not only entertaining but, more importantly, insightfully educational. Thank you for keeping the problems as well as the successes intact in them.
On the subject of carburetors, having sat for decades with perished fuel in them, the methodology that I've employed over the years is a little different than what was displayed. Now, my preferred method is to let chemistry make the job much easier.

1. Remove the bowls and thoroughly submerge, soaking them in WD 40. (WD 40 not only loosens everything, it also rejuvenates gaskets and seals temporarily without damaging them.)
2. After the usually daylong soak, remove the needles valves, jets and emulsion tubes freeing the passages, working the freed floats and/or slides, needles and pins leaving the majority of the assembly intact. Use low-pressure air to force the lubricant through needle valve passages. Ensure that screw positions are noted for re-assembly.
3. Use a toothbrush, the softer the better, lightly scrubbing the floats, bowls and the internals of the carbs. Leave lubricant in place unless really varnished. If severely varnished rinse with the lubricant and repeat.
4. Re-assemble everything, minus the bowls, to prescribed positions taking care not to damage gaskets and delicate seats.
5. In a bucket with a lid, re-submerge everything in fresh alcohol-free premium gasoline.
6. Attach a variable speed sander, I use old bicycle innertubes, onto the outside of the bucket with the rubber pad contacting the bucket's lid, minus abrasive, and turn it on to the absolute lowest speed and leave it on for some time. (This acts quite well as an impromptu sonic cleaner.) Vary speed accordingly to suit your needs.
7. Take the whole assembly and bowl covers out of the gasoline soak, shake off excess, and blow low-pressure air over everything in order to dry the pieces. (This will usually dislodge more debris.) Rinse and repeat if necessary.
8. Re-assemble the bowl covers and install on the engine, ensuring that everything functions as it should.
9. Attempt to re-start the engine.
10. This whole process usually takes far less than two days. Other checks are done while waiting for the chemistry to work (Actual hands-on time is quite minimal due to allowing the solvents their time to work.)

This method may seem a little strange; however, to ascertain the condition of an engine quickly before necessitating a complete teardown; it works quite well. My experience has been that of 95% success: Your results may vary. Some carburetors are beyond the scope of this procedure. I don't do many restorations and the pieces that I do work on are for a quick flip and re-sale to somebody that will, or simply enjoy the vehicle as is until a full restoration is warranted. I also use this procedure on pieces that I eventually fully restore to quickly sort out what I've gotten into.
It is my hope that this is helpful to you and your subscribers. This has definitely helped save time and money over the years without damaging precious parts. Even when dealing with automotive carburetors once you look inside then soaking them in fuel will usually get an old heap quickly sorted and running again.
Thank you for the instructional video and allowing me to pass on some knowledge.

Blimey! It would take me years to rebuild those ( and I'm sure I would end up with leftovers). 😄

You've unwittingly saved my day. This morning I dropped off my bits and pieces at Warners for plating. Came home and started watching this. Then heard your comment about high tensile bolts going brittle though the process. I knew I had handed over a dozen or HT bolts. I just rang Warners and they can oven bake them to de-brittle the bolts for me. Thanks Peter, saving the day with little tips here and there. Imagine driving along and having control arm bolts fail! Cheers & regards Steve.

Holy crap! Those carburetors are a HORROR in terms how they are complicated...

Good luck with all those linkages, lines, springs, clips, retainers, screws, etc, etc, etc.... when you put those carbs back together, (hehe)
Seriously though, you were haulin' ass ripping those apart. I was half expecting an AvE style "TIME!" when you were done.

hey pete, as always i find you vids exeptional, i have not finished  watching this vid yet but i thought it worth mentioning, in this vid and your last i agreed with the fact that there are loads of carb rebuild vids out there, but there is one vid i have not found yet,. and that vid would explain the most basic principal of carberation, and i think you are the perfect teacher to do so, as you know most people think that fuel is  "sucked" into the engine, when in fact it is pushed into the intake by atmospheric pressure. yes, all vids cover the basics, "is the main jet clean? is the idle circuit   clear? does the foat leak? dose the needle seal? sure. all important checks, but if more people understood the "venturi" effect and what is actually happening, it would be much easier for them to find thier problem, i cannot beggin to tell you how many small engines i get in my shop for a "run then stop run then run again" and all it needed was the fuel cap unplugged or replaced, sorry for the long comment, but i couldnt say it shorter i think.

That's a very big, tough-looking box of mystery...

hi peter nice video good one bob

If you can't remember you can watch your own video, always nice to have the kits on hand

Thanks a lot for your videos Peter.  Yeah I would not have separated those carbs.

Good work engine looks brand new.. Xc

My 750 took a while also.

Oh man I am getting so happy its so close to getting done!! Cheers!

Adjusting the idle mixer screws must be a nightmare on a engine that has a carb for each cylinder.  I don't know enough to even guess at what other challengers come with this.

Thanks for doing the carb video.  It's going to be fun to watch you get them put back together.

Wow, I just randomly stumbled across your channel and the videos you have produced are thoroughly enjoyable, and I'm no mechanic.

Superb job buddy! The engine looks absolutely beautiful. Yeah, those late-model carbs are ferocious hey? Probably 90% of CB750s were scrapped or parked because of carb problems due to being parked with the float bowls full. It's gonna be almost a shame to put them back on the engine once they're all beautifully rebuilt, haha! Can't wait to see what's in the box!  Cheers from here; Frankers says hi to Annie!

I as taught to pack a dry oil pump with vasoline petroleum jelly. It’s compatible with almost any lubricant. I don’t like to use grease because it shows up in oil samples. I built a prelude pump out of a Detroit Diesel fuel pump. It has a relief valve set at 70 psi and an easily adaptable square drive. An in line oil filter is used. Like your videos...keep it up...thanks

That varnish softens up in hot water. You could have boiled them for 10 minutes or so and it would come right apart.

Thanks for doing the carbs on video Peter. At the very least, you can use it to re-assemble! Lovely work.

Those carbs though.....  We have faith in you Peter.