Motorcycle

I have a 1976 Kawasaki kz400. It has sat for some years but was well taken care of. I started riding it and it rides great for sometimes 20 miles and sometimes 1-7 miles. The issue is sometimes it will start to run really rough and I have to give it more throttle to run sometimes almost full throttle but it still just goes slower and sometimes the power will surge. But if I’m rolling I am able to hold the clutch and keep reving the throttle until it dies. I just had the carbs cleaned using an ultrasonic cleaner. I checked the compression and I checked for vapor lock with the gas cap. I changed the spark plugs, oil, oil filter. Does anyone have any ideas where I should look next?