Criminy, that's awful. You really need to fix that.
Most of what I hear is transmission gear clack, and is caused by uneven cylinder firing pulses I can also hear.
I think I described the gear clack before. All the trans gears are always meshed. But, they aren't locked to a shaft until an engagement dog is moved sideways on that shaft.
So you have ten gears and each is paired with a mate. The gear tooth mesh is not zero tolerance, meaning there is space between teeth both frontside and backside unless there is a speed change for either of them. Yours are going into oscillation and alternating contact frontside and backside. Your clutch basket mass changes the timbre when you disengage the clutch. The clutch plates can rattle in the clutch basket, too. Which is yet another noise for changing /alternating rotational speeds.
The clack is bad enough on yours that it is unlikely you could even hear the cam chain tick. But, I would ensure the tensioner shoe is really keeping the slack out of the chain. Changing the cam position relative to the crank will add to uneven firing pulses.
You can probably feel the un-eveness in the exhaust pulses among the four pipes.
Usually, a carb balance takes care of it, if the engine mechanicals are sound.
Do you have comparative cylinder compression numbers?
Are you absolutely certain that the valves are adjusted properly?
Could you have cam lobes worn unevenly among the cylinders?
After you have total confidence that the engine mechanical is working as it should, that only leaves the carbs as the problem source.
Given the carb balance was done properly and and evenly, something is different among the carbs regarding fuel and air delivery.
Try to feel the exhaust for the oddball pulse strength and/or irregular pulse frequencies. Like does it fire 4 out of five regular intervals. Are they all different or just a couple? It would be helpful to isolate down to specific unreliable cylinders.
If you have exhausted any hope of finding a difference among the 4 carbs, then you might be able to compensate with the IMS on the cylinders firing differently from the dominant ones. Tweak them to make the weak ones stronger on the exhaust pulses. If the IMS needles and seats have been damaged, the number of turns won't have the same effect compared to the others.
Here's something to try toward that end. At idle, you should be able to stop any chosen cylinder from firing, by closing the IMS. Find the threshold point where you can make it come and go (feeling the exhaust pulses). Do the same for each in turn. All the while tweaking the big idle knob to keep the idle RPM at a fixed indication.
This process will be reiterative. Get a fan on the motor as it is going to take some time. You will probably have to spring for the good right angle screwdriver for this trial, as well, because you will have one hand on the exhaust tip and the other on the adjuster.
I have a nice tool (the morgan carbtune) so I trust the results.
Check your tool by hooking all four of the indicators to a single vacuum source, to verify they all read equally over the entire indicating range.
