YZ426 Head

So I decided to replace my piston this week and have two questions,

1: What is the best way to de-carbonize the head without removing the valves (don't have the tool, and I used the solvent test to verify no leak at seat)?

2: After pulling the piston, I noticed what appears to be burns on the crank on either side next to the connecting rod. Is this something to be concerned about?

Thanks in advance for the help.

1. Unless it's caked on real bad, don't worry about it. It will happen again once you run it for a while.

2. I've heard it's from heating up the journals at the factory when they install the pin.

The heat bluing is indeed a normal part of the manufacturing process. As long as the big end of the rod looks normal, it's fine.

Fill the intake with straight fuel injector cleaning additive, and then use it to clean up the combustion chamber. The carbon will be loosened and mostly flake away as the engine first runs.

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