Originally Posted by Davidka
You're fine, if anything, you look a little rich.
Yes, make sure to clean the inside chamber including the carburetor, check your bearings while your at it. They can go bad pretty fast depending on application and type of bearings used. This can improve the reliability of your engine. Clean it up, by cleaning outward away from the piston so you will not get dirt in the piston slot and ruin your engine. You seem to be getting a little more oily residue than is normal, which is why you have so much sandy grit caked up on the surface. It is normal to see a dark color on the piston head.