Gp1200 cylinder question

[Robfromga]

New to me ski with 10-15 hours on the motor.
Motor was rebuilt by the PO
Checked compression, front cylinder had 100-105, the other 2 had 125
Added oil to the front cylinder, no change.
Took the ski for a short GPS speed test, retested the compression, the 2 still at 125, front now at 70.

I took off the head thinking gasket leak. I found a slight piles film beteem the cylinder top and the gasket on the low cylinder, approximately 50% of the circumference. So I'm thinking bad gasket seal.

Well in better am light I see this just above the exhaust port. Please say this is OK and I don't have to remove the cylinder.

[Myself]

That appears to be a gouge and maybe some fresh wear on the power valve. Possibly a ring spun, lost a locating pin, power valve keeper about to fall off, you need to pull it and find out what's going on.