An oily discharge..and an inability to control it...

[canyncarvr]

Changed my head gasket. Whadd'ya think?



I wiped the mating surface with a rag..gave it a 1/4 turn on a piece of 400 to get the gasket sealant loose..but that's it.





(Where it's dark is where it's shiny)








Kind of a funny pattern, ain't it?

[IdahoCharley]

First off it looks like your head is fine.

Gasket picture (third from top) - between arrow and x and between coolant hole and cylinder - does the gasket surface appear to be raised?

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?

Cylinder picture - Looking at 12-1 o'clock in the picture - traces of cylinder combustion products beyond sealing ring? Or do you think possible it was the kips sub-assembly leaking and that was letting combustion byproducts get into this area? (look at the gasket and compare left sub-port to right sub-port in the picture)

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've got a theory - well sort of.

[Julien D]

Have you stitched it back up yet? Still acting up?

It does indeed look like the head gasket was leaking where your arrows indicate. Was that gasket ever re-used? I have successfully re-used those gaskets only after spraying them with that copper gasket sealer stuff for metal gaskets.

The deposits on top of your piston look healthy from what I know. Looks to be nice and brown, not too black. The clean spot does match up with the suspected leaky spot on the head gasket, no? That'd be further evidence of a leak right there.

I'm glad you're tearing into it. My question is.. What do YOU think??


Like the thread title. Was half expecting to see a picture of a soiled depends or something.

[canyncarvr]

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!

[Julien D]

Hopefully you've got it licked. It is a good thing there was no damage to the head or cylinder. If it was leakin, must have been just a little bit. From the pics it sure seams the head gasket was at fault.

I'll be looking forward to an update after you get to ride it some!

J.

[IdahoCharley]

LOL on the thread title comment ".... Was half expecting to see a picture of a soiled depends or something. "

I believe it was a leaking head gasket allowing some coolant into the combustion area. i.e. high water vapor content in the combustion chamber during the power cycle will clean the piston on the side it is leaking seen this a number of times.

The total cylinder head being as clean as it is was a little weird. On snow machines when leaking occurs it normally does not totally clean the head but what I have seen has been normally catosphetic failures. Of course the sleds normally run some healthier compression ratios.

Drowned bikes that were restarted and run with wet filters and torn down afterwards with very little run times show some similarly to yours with the exception that the piston is also normally scored on the inlet side of the piston due to lack of oil. Should not be a problem on your bike due to where the suspected leakage was occuring.

What I questioned was the evidence of combustion gases around the right kips shaft (which you explained via a loose head nut) and the appearance in the cylinder picture of the optical appearance of a raised ridge between 12 - 8:30 in your picture. I'm now thinking that was a path for some steam channeling around the reinforce ring on the head gasket - THAT area for the life of me looked raised in the picture and that totally threw me for a loop.

Theory - I believe you had a leaking head gasket which seeped a little coolant into the combustion chamber during the intake cycle and allowed some combustion pressure into that same area during the power stroke. Probable transitory type leakage during a specific period of time when the bike was heating up and/or cooling down. Elongation of the cylinder and expansion of the head likely allowed the head gasket to seal most of the time.

[canyncarvr]

Agreed on all counts on the head..prolonged exposure, aftereffects of drowning.

Something there is no pic of is the condition of the cylinder. Can't look real close with the cylinder in the bike..but I was surprised at its condition. I saw no marks nowhere. None. I don't mean no gouges, no scoring...I mean no marks of any kind.

This top end was one'a those 'hard break-in' setups. I warmed it up..and immediately flogged it.

I've been a believer in that break-in method for awhile. The looks of this cylinder cinched it.

'Cool downs' and 'partial throttle' usage...BAH!

[RBD]

You are going to pull the cylinder and at least re-ring it, aren't you?

Ron

[canyncarvr]

You are going to pull the cylinder and at least re-ring it, aren't you?

Ron

That would certainly be the smart thing to do....and I should at least do that.

I have a set of rings...and a piston for that matter..sitting in my box-o-parts.


Alas...I didn't.

Partly, I'm curious to see what the effect will be of just the head gasket replacement.

More than partly...I'm just not too smart. Heck...take out the 'too', even!!

[Julien D]

If it doesn't need the piston and rings, why change 'em?

[canyncarvr]

Safety in preventive maintenance?

Following a head gasket failure that introduced water into the cylinder, I'm sure it would be a good idea.

Still...I want to know a couple of specifics about how the bike operates/performs with JUST the head gasket changed and hopefully doing its job. If I replaced anything else, I'd never know.

It's worth doing some of it twice to find out.

[canyncarvr]

First ride with the new gasket yesterday.

Didn't loose a drop of coolant.

Got it plenty hot what with messing around in the wet clay of the day, too. Not a gurgle. Gee....maybe 50/50 really is different from water for coolant.

Losing coolant on a regular basis, I'd been just adding water. Antifreeze long gone.


The bike ran better with a leaky gasket. Took a good bit of fussing with the airscrew to get it back in shape. Ended up around 10º 'in' from where it had been..a bit less than 2 1/2 out.


So...th'ar 'ya go.

[Julien D]

That's strange. I would expect it to run better WITHOUT a leaky gasket. Seems it could have been puling air IN through there perhaps. In which case you made it richer. but you had to go richer on the airscrew to make it right, so that theory is shot to heck.

Either way, glad you got it sorted out!

[canyncarvr]

I left out that it starts a lot better cold. That's nice!