Oil fouling plugs after top overhaul

[Fliegezeug]

Continental O-200 on C150 M here
replaced cylinders
ran engine about 4 hours
oil keeps fouling up plugs
detonations when leaning mixture
bore scope shows oil squeezing out between cylinder walls and pistons
piston rings are correct according to mechanic.

What could be the problem?

 

[Cactus Charlie]

Are you following the specified break-in procedure for your engine and cylinder type?

If you specify the cylinder type maybe someone will have advice for you. My only experience is with Lycoming O-360 and IO-360 nitrided cylinders which required more than 10 hours high power running with a rich mixture.

This

https://continental.aero/service-bulletins/pma/sil012.pdf

and lots of other advice found with a search for "Continental O-200 cylinder break-in".

 

[Fliegezeug]

Thanks for the feed back.
They are chrome-plated cylinder barrels.
You are supposed to fly the plane for break-in but it's out of annual so I cannot fly it.
I have been running it on the ground (mostly with cowling off).
Btw, the link does not work.

 

[Cactus Charlie]

TCM appears to have withdrawn the document. The link was valid when I posted.

I suggest you contact your cylinder manufacturer or overhauler for approved procedures. You said yourself that "You are supposed to fly the plane for break-in" and then you ask "What could be the problem?"

I think you answered your own question.