Re: Scratches in the bore
If you load a two stroke engine, or rev it up too much before it warms up enough, the piston skirt can rub in the bore and cause the lines you see. It's called "cold seizure".
Also, if your plug is grey, or closer to white, that's too lean and hurtful too. Too much oil in your mix can make the fuel/air mixture leaner, and that's not healthy either.