Bushing engines have some end play in the crank, which is normal, may seem like a lot however things do line up when the prop puts pressure on the crank.
You could look down the exhaust port and or remove the back plate of the engine and have a look inside, should be shiny, if you see black like when you polish aluminum then things are not good. Carbon in the exhaust port and on the piston and cyl head is normal for a used engine. I think you will find that the engine is good.
If you run the engine, check the exhaust, oil discharge should be clear to amber with no black, If you hear it squeeking or making a squeeking noise, usually the crank bushing, check that your fuel has at least 20 - 22% oil in it....
Hope this helps
Richard