I would replace it if there are noticeable marks on it, even I would replace it if those marks are not very noticeable but I could feel them with my fingers.
Doing a tach test will not tell you much but the sound of your engine is quite different and tuning is hard as it tends to overheat.
It is going to be a good idea to change the liner, piston and bearings too, because the most common problem resides on the bearings. (they expel the most particles that commonly ruin any engine)
Also check the retainer of the piston rod (A tiny wire that keeps the tube in place) as this wire has happened to broke and cause the ruin of the liner and piston.
I hope this could be of help.

Alfredo