The shift shaft was machined so the shift fingers turn the shift drum more efficiently. In stock form, the drum is turned only partially with the shift shaft fingers. The rest of the turn is accomplished by the shift detent rollers pushing on the shift star points with spring pressure. This is why when the points become rounded the result is poorer shifting. The shifting was improved by allowing the fingers on the shift shaft to turn the drum farther before relying on the detent spring and roller to finish the shift.