Johnson 60 sluggish and stuttering at WOT

[Kruegs35]

I just scraped the carbon with my fingernail and wiped it with acetone.

I had this same question on another forum and someone there claimed that the carbon wouldn't cause the problem, it was probably a leak in the head gasket. It was pointed out that normally carbon would be covering the entire piston, but the bare spots on each indicate that the carbon was being blown off by the leak.

 

[racerone]

No-----You can see that the piston is clean right where the fresh fuel / air comes in !---Almost every motor out there is running just fine with carbon deposits like that.