My kawasaki bayou 220 has a oil check window as a way to ensure the correct amount of oil is in the engine. The last time I rode, I noticed I was a little low in oil, and the window that wasn't covered in oil was covered in white smoke.

Any idea what this is?

 

are you sure it was smoke. If it is milky looking liquid it could be coolant in the oil.
Just a thought if that is the issue you have a bad head gasket.
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If that is the case start it up and watch the pipe there will be white smoke when you fire it up till it warms up.
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If it is air cooled that I am way off base

 

it is air cooled, i think it may be little water vapor.

but opinions are welcome

 

compression check- maybe a burnt ring or a scored cylinder allowing blow-by into the crank (where your sight window is)

also- don't know much about those motors- but if there's a clogged breather vent for the crankcase- it could be preventing gasses from properly venting...

 

+1
could be that too-


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