I see where my previous post is unclear, and where the statement is ambiguous.

I still think however that O-ring or outer seal failure on the MC21/28 is more common than centre seal failure, and would bet the traditional 50p that more often than not a new O-ring will fix a leak across the crankcase in the later motors. The MC16/18 certainly doesn't seem to suffer the problem anywhere near as much as the MC21/28. I know the (main) centre seal arrangement is quite different between the two, but I've (personally) yet to split an MC21/28 motor that's been together for any length of time where the O-ring's not in poor shape.
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Andy.
NSR-WORLD.COM

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