Hello,
Ive been working on this ongoing fault for a good few weeks and I've got to the point where I have run out of talent and knowledge!
History:
I have had it for 5 years and it ran great as it was used daily until I didn't and it was used occasionally. It developed a issue where during riding at speed on a long straight it would act like it would run out of fuel. I tracked this down to a blocked breather pipe on the tank. Why they run it down to the bottom of the bike so it can get blocked with crap I dont know... But all was good for a while.

I ran it up a few times early 2020 all ok. Late last year it would run but only if the choke was at 100% on. Any throttle would kill the revs and the engine would die. It could be ridden like this but would fail if I look the choke off. Also, not a ideal way to ride the bike! I tried fresh fuel at this point also but no joy.
So I clean the carbs out.
The problem remained. I then figured that either the jets were blocked or the petcock was having issues so I replaced both with a new filter that went inside the tank. The existing filter looked like it was restricting the flow of fuel so I was hopeful. I ran the engine without the petcock and there was suction on the vacuum tube that connected onto the petcock. I have also replaced the jets and other brass bits inside the carbs.

I put it back together and now it wont start at all. Engine spins well but it will not fire. Obviously I have done something wrong but not quite sure what. I think it might be the timing screws? Image attached, green and yellow cable pointing to the screws that I think might be the issue and I am unsure how to adjust when putting back together. I know that it will need to be balanced but just starting and running rough would be a improvement! Any ideas about what to adjust or check next? Cheers
There was fuel in the bowls so its getting to the carbs ok.
Air filter is clear with nothing nesting in there.
kill switch isnt on!

Have you checked for a spark at the plugs?

Have you tried fitting new plugs and are they gapped correctly?

Checked the plugs and good spark on all 4 plugs.
However, 3 plugs are showing signs of carbon fouling (blackened ends). Although they wouldnt of suddenly done that and stopped starting it is sign of a fuel richness. Problems up to this point anyhow.

If you've a Haynes/Clymer/Honda manual that should have all the factory settings for mixture screws.

Any fuel in the float bowls. Full choke should get sum type of response from the engine. Green and yellow cable is pointing to mixture screw. 2 turns out from fully seated is a starting position.

Pretty sure there was fuel in the bowls. I turned them upside down and plenty drained out again.
I have ordered new plugs and I will rebuild and update thanks.
I will also try adjusting to 2 turns rather than the guess, looks about right this time!

You could also try placing your hand across the inlet throat of one carby when craning the engine. This is a crude way to drawn fuel from float bowl into the engine.

An update:
Replaced spark plugs (CR9EK)
adjust the all screws to the 2 turns and put it back together.
No start. Its looking dangerously like a garage job at this rate!

Are you actually getting a spark at the plug?

When you are turning it over, how does it sound? Could you host a quick video and link it?

Will get back to you with the video.
There was spark on all 4 plugs on the old ones, I have not tested the new because they are new.
engine sound is just the sound of it spinning. You know when you try to start with the kill switch on? Its that, but yes I have checked that - many times!
Ive got a friend around to offer fresh eyes on it at the weekend, I may of over looked something daft.