Hi Stefan, yea the water here is cold so I run restricters in my cooling lines right behind the pissers. The restricters make the water spray out the pissers instead of poor. What i notice is a difference in the spray when the oring starts to leak, it kinda intermitantly spits/pulse more while spraying.. it's kinda subtial. If I pull the restricter out I can no longer see the issue, so the restricters give me early detection. If I pull the spark plug it starts to look cleaner than the other cylinder, piston starts to look cleaner, but this is early detection so they are still dirty not steamed cleaned completely yet. If I didn't run restricters I have no idea how long it would take to finally notice it.. hand lapping the top of the cylinder with a stone and oil and new orings restores normall spray. My sleeves move a lot, cylinder needs decking too, but I service it this way till over haul time, since on last bore...I only get maybe 6 months out of the compression orings... making matters worse it looks like my domes were hand sanded, lots of sanding marks around the grove which tears up the oring.
When I first got the engine it had just been fresdhend up and an oring had come dislodged and was sitting out of the grove on assembly, that was real obvious when I started it and ran on the trailer without restricters, the pisser pulsed and spit bad, the cooling line even shook, real noticeable. Then on a restart it hydrolocked and stripped the bendix and starter...
I have 2 outs off the head, going thru 2.77mm or smaller restricters right behind the pissers.