White smoke out of breather tube?

[twomancrew]

Blowing white smoke out of breather tube when starting and shutting bike off. Oil on dipstick did not look discolored when I checked it when I first noticed problem. Rode right back to truck. Coolant low am going to check and see how low. Am going to drain oil and check today. Fully expect to find coolant in oil. I know I am going to have to take everything apart and hopefully it is just a gasket. Going to put new piston and rings in while I am at it.

Bike did not overheat. Runs great.

Just wondering if there is a standard or non-standard issue that I should check for? Could it be more serious than gasket?

08 YZ450F w/ 478 big bore. Replaced intake valves this summer when I did big bore. Replaced timing chain and tensioner @ same time.