Cylinder Condition

[luca5927]

Hello, I recently got a new echo cs400. I have run it for a bit and I took the spark plug out to make sure everything is doing okay. The cylinder looks to be in good shape aside for the black stuff in the following photo. Does anyone have any insight as to what it is, and what issues it can cause? Compression tester reads 130-140psi. the drops on the side of the cylinder are fuel. I use Tru fuel 40:1 and always let it warm up.

 

[luca5927]

it also seems to be present around every exhaust/ transfer port I can see from the spark plug hole.

 

[Brushwacker]

Carbon. Air to fuel mixture ratio is most likely to affect the amount that accumulates. Keep your air filter clean, fine tune the carburetor if it has adjustments and don't let it idle too, too long. At start up it will get extra fuel from choking it and at idle the saw will not burn clean like it does under load properly tuned.