1977 Johnson 55hp 22psi difference in cylinders

[catfishin_welder]

I've got a 1977 55hp model 55EL77D. I've rebuilt both carbs. (Fixed jets model) Adjusted throttle cam, etc per manual specs.Coils are good. Spark covers 1/2" on tester. Fires right up, revs super high at start up then instantly dies. On both my compression testers I got 152 on top cyl and 130 bottom. I know from experience that I'll never be able to properly tune with that much difference in compression. I looked into the cyls with my scope and can see no scoring. Carbon deposits look similar on top of both pistons. Next step is to pull head and check for compromise in gasket. I'm thinking rings. I've ran motors before with ring issues and as they heated up rings more or less worked themselves out (freed up). Problem is I can't get this one to stay running. Before I tear head off, is there anywhere or anything I've neglected to look at before doing so? Thanks for any advice. I've been wrenching on 2 stroke OBs for over 35 years but I'm always learning with each motor and appreciate folks ob knowledge

 

[fdrgator]

Most people run them till a ring breaks. But yours won't keep running. Maybe you got lucky. Water intrusion??

 

[racerone]

It is either a scored cylinder or a leaking head gasket.----You would know to pull the head to inspect.

 

[catfishin_welder]

Yes. I'm in process of repairing the remote box then going to pull the head, check it for level, put a 2$ wet sand on granite head work on it. I'm hoping the head gasket has been compromised over the cylinder damage. Ones an easy fix, the other is more work than I'd like to do to this motor