White smoke coming from exhaust. Help with spark plug reading.

[myntmaskin]

I recently got my XS400 '82. When i rev it there is white smoke coming from the single exhaust and some coming from the crankshaft ventilation tube. The right spark plug was fine but the left one is completely drained in gas or oil. Using the picture for reference, does this indicate a very rich mixture or oil in the combustion chamber?

I'm pondering if its some kind of broken o-ring in the left carb or a faulty head gasket, or something else. I don't have a compression tester, but might get one if I can rule out other faults.

All help appreciated.