I'm using Flash .12 PT engine on serpent 747.
Recently, I disassembled my engine and checked it. (Just regular check.)
And I shocked there were too many scratch on top of piston and under-head.
But, the scratches are only top of piston, the sides are clean.
(I attached some pictures of piston and under-head.)
I've never seen like this before, so I can't imagine what happen in this engine and what is caused of this problem, what should I do for the next.
I mean this is just OK to keep using or do something to avoid further bigger problem.
Please give some advice.
Fuel : O'donnell Speed Blend 25%
Plug : O'donnell 77T