Along with the seal goes the different crankshaft drive sleeve 67 2071, listed above. This has a smaller periphery to fit the seal lips. Earlier type has a larger periphery to be simply a close fit in the crankcase. Forum posts about this part abound, some are plain, with a smooth edge, some have a scroll. Fitting a later smaller sleeve to an earlier none seal engine is a simple mistake, it all fits fine, but primary case will fill with oil. If you have a plunger bike with this syndrome, there's a possible answer.
Early non seal crankcases can be machined to take the seal, and assembled with the later drive sleeve.
Later S/A engines use a different sleeve, which changes over the model years. Early ones run on the seal, later type has a spacer. Seal itself is the same part for all models/years since its introduction.
Swarfy.
