A freshly rebilt 400ex with a new piston with new rings correctly jetted carb. It was filled with two quarts of oil.

It was started for the first time jesterday and ran good with plenty of power. Parked it and this evening seen oil trails all in the grass from riding it I went into the garage and seem a large ammount of oil i started looking for where it was coming from. It was coming from the drain plug in the bottom of the airbox. i traced it back to the carb. Could it be a cracked head?