[esq'z me]

It is 10mm but does feel a bit loose as it is cast, not machined.

 

[esq'z me]

Glad to hear you have figured this out....yes, it was condensation in the crankcases, a normal by-product of combustion. Yes there is a metal plate on the inside of the oil level window (same on all bikes) that will trap frothed oil/water if present. A good long ride would have evaporated that moisture. Getting the old oil out also accelerated the evaporation of residual condensation in the crankcase. Even though the old drained oil doesn't look like it, it was holding that condensation in suspension.
Ride on !!