I've also seen other 2-strokes (not my 250r) that smoke significantly at start-up because the fuel bowl fills up with gas and oil, and a lot of the gas evaporates, leaving a mixture that's really heavy with oil in the carb. It will smoke bad at start-up, but then clears up when all that extra oil is burnt up and you get a normal mixture in the carb bowl.
My little LT80 is notorious for that, because the oil injection system will leak into the carb. It smokes like you wouldn't believe for the first few minutes.
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