Kawasaki 1981, 550 ltd jerking

Hi can anyone help. Cleaned carbs, replaced plugs, leads, coils ,air filter,oil filter and oil, balanced the carbs and the tank vent is clear well seems to be think it vents off a manifold on the carb two pipes dangle from the carb and go under the seat. The problem is once warm slow riding is just jerking , ok at speed. It's got electronic ignition.
Any help appreciated 👍