White smoke usually means poor combustion, which could be due to poor compression. However it could be other things such as a poor spark plug, retarded ignition or poor fuel vaporisation. Retarded ignition is not all that likely, since AFAIK it is not adjustable. If your spark plug, carburetor and air cleaner are all good, I suggest you inspect the side of the piston by removing the muffler and looking through the exhaust port. If the piston is scored, it is possible that would cause the problem even if the rings are OK. (Sometimes a previous owner has run the engine on straight petrol, which will often score the piston.)
If the piston is not scored, it is quite likely the rings are worn. The simple approach is to remove the cylinder, and inspect its bore. Unless the engine has been run without oil in the fuel, or without an air cleaner, it is likely to be good. If so, honing it is not going to make a lot of difference (except it will increase piston clearance, which you do not want). Remove a piston ring from the piston, and fit it into the bore so you can measure the ring gap with a feeler gauge. (Let's face it, you'll probably be able to measure it with an inch ruler). Unless the engine has been contaminated (no air cleaner) or run on straight petrol, it is likely that you'll just need new rings and a general clean-up. Check the bearings and seals, of course.
