I have a 1976 Kawasaki KZ750 B with 13k on it. Ive ridden over 500 miles since i bought the bike two weeks ago. It has ran perfect for me until yesterday. The bike will start fine. She idles decently once warm. Unfortunately, every time i shift into gear and try to take off she spits and sputters. If i shift below 3000rpm, she doesn't jerk or sputter. If i try to go over 3000 rpm in gear, she starts jerking, popping, sputtering and the occasional backfire. In neutral or in gear with the clutch pulled, i can rev to the redline without her sputtering. Other than the obvious carburetor problem, would there be anything I'm missing? Ive changed spark plugs, i religiously use NGK plugs. Oil is new, oil filter is as well. Could there be an internal problem in the motor or transmission? I plan on buying a carb rebuild kit within the week.