Brian, I very distinctly remember the day that I discovered what you just said. It happened after McCullough changed their design on the crankshaft. Just a small radius, (stress riser is what I think they call it) in the shoulder of the crank, where the clutch butted up against the shoulder, so the washer needed a matching radius on the ID. Not all that easy to see, and if you put it on backwards, (the radius was only on one side of the washer) the clutch would behave irrationally. lol for lack of a better word.