I've seen some smoke like that on rare occasions. One time my dad brought out the '77 Maico and was getting pissed at it because the points were off (they'd been off for twenty years) and so he was taking the engine to its absolute limit on this big open gravel road. Then he rounds a corner at about nine hundred miles an hour and sees a cop waiting for him. He hauls the bike down and just barely manages to stop in time, tires skidding. I thought that was quite impressive, given that the cop was quite a long way from the corner. Anyway, I pulled up a little while later on the 120 and about a minute later noticed that there was some smoke wafting up from his silencer, like there was a giant cigar burning in there or something. I had to struggle not to laugh - What was the cop going to think of THAT in the middle of August, in a forest with a long and proud history of burning to the ground? It was a weird occurrence, not because of the smoke, but because it's not every day you see a State Police officer cruising gravel roads.