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Bore scratches

Engine Building Fundamentals

Discussion and questions related to the course Engine Building Fundamentals


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I have my head off and noticed some scratches. They don't seem to be deep, running my finger nail over them I don't think I can catch them but I might be feeling a change in texture, it's hard to tell.

This is a high revving, 9k rpm, supercharged jetski motor running 17psi with about 62 hours of run time.

What could have caused these and anything to be concerned about going forward. I really don't feel like taking it apart :)

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looks like dirt, carbon and debris getting trapped ?

The ceramic dome coating I got on the pistons is flaking off, I'm thinking some pieces of that might have gotten between the ring and the bore.

Those scratches are what I'd expect to see from minor debris. this can be a result of a lack of cleanliness during assembly or the introduction of fine debris into the engine while running. What you have there is quite minor and while it's not ideal, it's not necessarily a problem either. Unless you're freshening the engine or doing other work to it I wouldn't be concerned.