Fuel line air bubble

[oldyam80sg]

Years ago my bike ran fine until I had an issue like yourself.Cleaned carbs so I though and would run fine,go up a hill,runs rough.Finally took and cleaned those screens in carb cleaner and like a new bike.I run 2 fuel filters and have the Pingel petcocks and Pingel fuel valve.No issues now.

[donebysunday]

I had one doing what sounds like what yours is doing, (bike had sat for a few years) the tank had old fuel residue in it.
As the engine warmed with fresh fuel in the tank the engine heated the fuel in the tank and released this old varnish into the system and cause it to spit and stumble.
I cleaned the carbs over and over but after a few miles same thing returned, spit, stumble, cough.
Finally let the tank soak in cleaner for 3-4 weeks, drained, put back to use and fine.
Did not want to waste the fuel so with the cleaner in it dumped it into my fuel injected car. Less than a block from home with the car, spit, stumble, cough then all was fine forever more.
The fuel pump in the tank on the car is at the bottom so it picked up the heavier junk that settled, forced it through the injectors and once this was done fortunately all was fine.

, make sure it's air. I had one that looked like air in the line, could not get it to move. I cut the line right in the middle of this bubble and it was like vaseline.
This was old ethanol fuel residue, tank sat on the shelf for 3 weeks, an entire bottle of chevron techron ( not the weaker chevron with techron ). The chevron techron with a full tank of non-ethanol fuel