I replaced the mechanical seal in my 1995 VN 750. I got it all back together, started, and ran it without any oil or coolant leaks.
But when I checked the oil sight glass I noticed what looks like white foam (a thin layer) on the top of the oil level.
I drained about a pint of oil, and there wasn't any indication of moisture. I guess I should have drained the whole crank case.
The bike has been in my shop since the cold weather set in, and has been in a 40º to 60º F environment.
Any suggestions?
Bob

If by mechanical seal you mean water pump seal, then maybe some coolant made it's way into the oil when it went bad. Use some motor flush, or at least change the oil, and try it again.

I don't think that the coolant invaded the crankcase through the mechanical seal, because there is no coolant seeping out of the drainage outlet pasage.
Maybe it isn't moisture, but oil froth?
I'll drain all of the oil tomorrow to see what's going on.
Bob

Oil does foam slightly and moisture will build up it the engine is not run for long periods to burn off the moisture. When I first got my bike I only drove it to and from work which was only 2 miles. I had to change the oil frequently because it stayed milky. Now that I ride it for longer distances there is no more problems.