Kevin, we gotta ask some questions about your new purchase. First, did you see and hear it run? If so, did it smoke a lot on start up then settle down to no smoke? Or,did it smoke a lot and keep on doing it?
Was it missing, popping, making any clattery noises?
If it seemed to run pretty well but just smoked some, it is not likely to be a sticking valve. Be sure to check the oil level, and smell the dipstick oil for possible gasoline odor. If it's overfull on oil or diluted with gas, it will smoke. Also if it was parked on a down hill (nose down) for a long period, the muffler could have a bunch of engine oil in it.
It's very easy to take the spark plug out, remove the valve cover, rotate the engine by hand to watch the valve train work. Probably needs the valve lash checked / adjusted anyway.
That Kawasaki single is a very reliable engine, but I have found the rings worn out in one that didn't seem to have been abused or have a lot of hours on it. Don't know if it ever had the first oil change as it was a used machine my friend got with a house he bought. Ring job cured it.
Let us know how it goes.