weird mark on piston dome. With pic.

[hawktoy85]

this is a pic though the exhaust valve on PTO side piston. Looks like melted metal? wash looks good on both pistons. Rode sled pretty hard for about 2 hours with no issues. except for this I found when I got home.

Anyone have any ideas?

Background: Just did top after complete failure of Mag side. Have ECU 21 error after rebuild. I still have not resolved my ECU 21 issue either but have narrowed it down to a short. A/F was perfect all day. Ran solid at 8 lbs.

Pic is hard to decipher. But round circle is center of piston and has weird marks in 2 places.

Sled: 2009 M8 with twisted turbo on 100LL at 8 lbs

 

[Rixster]

That is strange, Isnt the 21 code for the knock sensor? I did a top end on my buddies 07 m8 this year and after the rebuild the knock sensor code will not go away. It doesnt affect the way it runs at all, just an annoying flashing light.

 

[sunbather1969]

pic

On my snapon cam if I saw that I would say metal but my picture doesn't look like that is that the best you could get if so id be pulling a head. My pics are much clearer what other side look like you try putting light in a piston hole and taking pics

 

[hawktoy85]

I guess panic was a little premature. I reached in there with a screw driver and and it is just some sort of greasy stuff. maybe some residue from the blown piston. No damage to new piston. I think all is ok.

The other side looks perfect.

Rixter: The code is annoying. I changed the knock sensor for $150 and that did not fix it. In the process of acquiring a wire harness hope that fixes it. But for now I'm riding it like I stole it.