Answers as well as I understand the questions:
Gasket picture (third from top) - between arrow and x and between coolant hole and cylinder - does the gasket surface appear to be raised?
It's as raised there as any other place there is a bead to the gasket..around coolant orifices and the cylinder itself. It does look to have more of a ridge to it due to the carbon that's in it. Certainly it looks 'deeper' than, say, 180º across the hole.
Your cylinder picture - Does the KDX cylinder really only have an raised sealing surface from 12 o'clock to 8:30 in your picture or is that some sort of illusion I'm seeing?
The cylinder has no raised sealing surface no where. It's flat. The difference in appearance in the 12-8 of the cylinder matches the gasket in the same area..more a matter of lighting and shadow in the pic. You may be thinking of some 'race ready' kind'a machine?
Yep a funny pattern on the piston - I'm betting your thinking your bike is running a little rich on the side of the piston which is clean: However your piston could also be "cleaned" as a result of coolant entering the combustion chamber.
I'm wondering about the latter of those two. I have been losing coolant..although it seems to drop a couple ounces and stay there. I've figured there's an 'air shock' effect in the cooling system that makes that happen..just like an 'air shock' in the forks (not that a fork air shock makes a funny burn pattern on a piston).
Have you stitched it back up yet? Still acting up?
Yep....and...don't know. There's snow and ice everywhere 'round here..not too conducive to riding. Heck...I doubt I could get up the hill to the staging area. Rode it around the house a bit..took off the rad cap. It had pressure. The coolant (50/50) looked pretty frothy. Didn't like that. Maybe after having been drained it's got some air pockets to work out. I did burp it at the head snorkle before I started it.
Was that gasket ever re-used?
Well now. Wouldn't that be good to know!
When I put this cylinder on (it's an OEM bore..took the Fredette ported USC one off) I didn't plan on keeping it ON for very long. ...guess that plan didn't work out too well...'cuz it's been on for longer than I usually run a top-end I mean to keep!
I have used KopperKote in the past. It leaves quite a mess behind when it comes time to clean it up..and it came off where the small round holes in the gasket block the larger coolant holes in the block. I scraped bits of KopperKote off my rad cap seal for a long time...
IF I 'memmer right, I used aluminum paint on this previously used gasket, having cleaned all 'sticky' residue off it first.
I think I won't be doing that again.
I'm surprised the head looks like it does. It was
spotless...not something I've ever seen in a 2T head. Sure was easy to clean up!!!
The arrow points to one of those places where the water jacket is restricted. There's some carbon goo (can smear it with a finger) there. There shouldn't be.
Also...at the 'X' the embossed ridges in the gasket that seal the combustion chamber have a good bit more carbon in them than elsewhere.
AND...both of those spots match the 'clean' washed part of the piston..and an area of the gasket where there was no paint visible at all..and it wasn't on the head or the cylinder either.
Note the water jacket block on the other side of the gasket. It's easy to see where the paint is..and where it ain't.
To top it all off (head? head gasket? top end? top it off..ha ha ha... I am sooo funny), there
was a bit loose of a nut on one of the studs right in the middle of that piston 'wash' area.
I'm surprised I didn't see ANY pitting or corrosion in the head or the piston. Coolant leaks tend to do that......
IC said I'd better get after it afore something bad happened.
I think I got lucky.
Thanks for the input!! Much appreciated!