Hello,
I have good luck stopping them from surging by replacing the jet on the side of the carb with a briggs and stratton pilot jet, part # 801308. Sometimes it's under a sticker or piece of black tape.
That lets it get a little more gas. The smoking could be an accumulation of oil from the exhaust u shaped tube under the deck. You would have to take the blade off and take the 4 bolts out
that hold the cover on. Then you could look at the exhaust port like Rivets mentioned.
Regards.
Jerry