Have an OS 40 LA (natural color) engine and took it apart for its yearly routine cleaning. Noticed while having the muffler removed and looking into the muffler port of the engine, viewing the piston, there is a thin slit starting from the top edge of the piston and extending downward on the side of the piston for about 1/2 inch. The slit seems to be very, very shallow, but concerned me nontheless. The engine seems to have good compression and always ran well. The engine is about 3 years old and never ran lean that I know. My fuel was always 10% nitro and castor based. Is this repairable or not worth any further attention.

Thanks,

Glowfuel