My Suzuki vs 1400 motorcycle bakc fires on the rear carb and runs rough on the rear cylinder is the problem fuel or electrics. I have cleaned the carb and put an on line filter on fuel pipe and cleaned the tank.But after the engine has been running for a couple of Ks the rear cylinder stopps fireing .What do i check next and how.

Take this unit to a PROFESSIONAL and have them clean and set and synchronize the carbs

if its carbureted- check fuel delivery on that cylinder- I had same issue on a 2 cyl Vulcan. it was dirty carb- restricted passages.

could be a problem in you sparkplug boot, carbourator, or a stretched throttle cable.

I think maddogcycle is right. One cylinder is running rich and the other running lean. It seems as though they have not been balanced properly and the mixture not accurately adjusted. The settings on these carburettors are critical and must be adjusted with the proper gauges. I'd advise you to have the carbs cleaned and adjusted and tuned to the engine for balance of inducted air flow and fuel/air ratio (mixture)

Did you sync the two carbs? If not the rear may be getting all the gas from the rear carb and none to the front. Twist throttle engine off and see if front carb cable is pulling the carb open.
Also unscrew the spark plug boot from the front spark plug wire and trim 1/8th inch off the wire and screw the boot back in. The plug wire end may be corroded on that wire.

mine is doing the same thing and i get a pop some times when i shift ,im running cheap fuel and i think that might be the prob.

is ther e no fuel mixture screw u can try adjusting

gas will varnish and then flake and stick in the needle valve.the hardest part your going to deal with is the correct syncing of the carbs.this is best left to a good mech with the proper tools

Hole in the float. It fills with gas, sinks and fails to stop the fuel flow

Check all your wires around your coils to see if they are tight or to see if any are broke. Check your sparkplug caps and coils with a ohms meter.