Break in period

[Tmall]

Originally Posted by Sean

This is what my piston looked like after 2000 miles with a hard breakin:

Explain how scoring on the thrust side of the piston would be caused by hard break in?

Likely causes, no cooling to the bottom of the piston, the piston rings had the gap close to each other, or fuel dilution of your oil. Unless that piston is coated, it looks like there is a ton of soot on top. Which leads me to think fuel dilution.

I'm far from an expert. Just falling KISS logic.

Edit: Where's the top ring? Were the rings installed upside down? Or in the wrong position?