I've often wondered how trash gets by the screen that is in the gas tanks. I know it isn't a total filter, but should stop most debris. While your looking at the fuel hose for degregation, look at the petcock diaphram.
Explanation: I recently replaced the diaphram in mysons petcock. During the repair, we found that the rubber on the inside of the diaphram (gas side) was basically gone. What was there, was decomposed/grains of rubber.
So, possibly the problem people are having is the rubber from the diaphram is getting into the carbs.
But, I have another thought. Did you look at the fuel line to see if it was kinked?
When you've worked on the carbs etc, you've removed the tank. (and moved the fuel hose)
The fix you found may have been a kinked hose not a blocked jett etc.
The hose can be fine when the engine is at idle. But the kink can restrict the flow and cause insufficient fuel flow. Or, it can kink/close more as it heats up or vibrates. I ran into this problem while on a ride. On thattrip, rerouting the fuel line solved my problem.
Ride safe, Ted