1978 Honda NC50 crankshaft oil seal size

Bart Staton /
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Hey all, Im in the process of cleaning out the cases of a severely neglected NC50. When I bought this one it was part of a pair, one was in good non running condition(its a runner now) and one had the left transmission cover just kinda hanging off to the end of the crankshaft.

From what i have been able to deduce, at some point the one in a better condition lost the wind up spring and the left side case was swapped out from the non runner. He didn't even bother to screw the halves back together so over time its been filled with all kids of dirt and leaves and the like. I think its salvageable but its going to require a deep clean.

While I am cleaning all of this it makes sense to swap out the oil seals since I'm having to pull everything apart anyway. I am just not sure on what part number or size the seals are. I've seen everything from 20X40X7 to 15X30X7 to 19X37X7 etc. and all kinds of parts numbers. Correct me if I am wrong but its Inside diameter, Outside Diameter, and the Height or thickness in Millimeters correct? So should I just be able to measure my crankshaft with a caliper and go from there?

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