I agree with the others that it's just excess oil burning off in the exhaust and/or combustion chambers. I worked in a bike shop and a girl rode up on a badly smoking KZ400 and wanted to know why it was using oil because she had stopped 2 or 3 time in the last 20 miles to have someone put oil in it. Well her problem was the oil was already above the sight glass, and when i drained it down there were about 2 to 3 quarts too much in the engine which had also sucked up into the airbox via the vent hose. There was about another half quart in the airbox and the filter was soaked with oil. After draing it down to normal, cleaning the airbox out and replacing her filter it still smoked some but started quitting as it sat there and ran. So to make a long story short make sure the oil is at a normal level and GET OUT THERE AND RIDE THE %$#!! OUT OF IT ! ! Get it good and warm so the oil will finish burning off.

 

Haha. That story reminds me of this one time I see this girl outside of the local auto supply with like 10 empty quarts of oil sitting next to her. I walk up and ask her were she is putting the oil. She states that her dad told her to check the oil in her new car and that she keeps putting oil in the engine put it will not fill up. She can see it through the fill hole. She then asks me if I think there is any damage done to the engine from it running that low on oil.

I almost passed out laughing before I told her to get it towed to a mechanic.