What color is the smoke that from the exhaust stack?
Different colors tell different stories on what is happening with the engine and if it's a problem or not.
One would have to assume that you are referring to smoke coming out of the exhaust pipe.
The reason I word the statement the way I did is that the previous owner of my B7100 was not familar with the "thermosiphon" cooling system and overheated it somehow. Shortly after I purchased it I got a lot of smoke (blowby) coming out the tube coming out of the top of the valve cover. The smoke got thicker, then started having drops of oil in it, then just started pouring oil out of the tube. After breaking down the engine, it turns out that 2 out of 3 compression rings had gone "soft"; otherwise the engine was in excellent condition still. I have been trouble free for a few years now.
While this is most likely not your problem, I'm sure that other B7100 (B5100s, B6100s and a lot of other small B-series) owners will be reading this post and I would like to see all of them be aware of the cooling system. And the next time they pull the radiator for cleaning, they should consider putting in a mechanical temperature probe in the radiator to monitor temperature.