The earlier sprockets are thicker with a raised shoulder on both sides while the later K and F models (77/78) only have the shoulder on the inside with the outside of the sprocket being smooth with no shoulder. The outside shoulder of the early sprocket will extend out past the end of the output shaft by about 2mm. I have used a head nut washer behind the big washer to keep from deforming the big washer on the sprocket bolt when tightening down. The front sprocket for a 79' CB650 is a correct 530 sprocket for the 77/78 CB750's in that it only has one raised shoulder on the inside and the sprocket will finish flush with the end of the output shaft. I use the CB650 front sprocket on my dragbike.