Exhaust port degradation...

[Forden]

I pulled my exhaust for the first time yesterday, and made a couple unwelcome discoveries--first, a PO had just installed new header gaskets on top of the old ones without removing them. WTH. Here's what they looked like removed:

IMG_2452 by Forden Photography, on Flickr

More disturbing (and related, I'm guessing) is that the exhaust port / gasket face on #2 was badly degraded/eroded:

IMG_2455 by Forden Photography, on Flickr

Anyone found this before, and what am I looking at here? A leaky header gasket adding oxygen and causing combustion to extend into the exhaust port? My brother suggested that, and that there was an acidic byproduct of that process that might be in play also, causing the loss of material.

I'm hoping there's enough material left to seal the new gaskets--"you need a new head" will not be at all welcome news. Ugh

Here I was feeling pretty happy with recent progress, just rebuilt forks and steering and did a bunch of cosmetic resto along the way:

IMG_2451 by Forden Photography, on Flickr

Thanks all.
Mike

[rphillips]

gaskets look kind'f normal, they just do that sometimes. I've not seen a gasket surface chipped like that. wondering if stacking new gasket on top of old gasket put too much pressure in there? Guessing it will be OK, but like you I'd feel better if it didn't look that way.

[Big T]

Give the port a good cleaning and see what you have

[Cipher]

Casting defect and the factory let it pass.

[bwringer]

I think there's still a gasket in there in that second photo.

And odds are that nasty bit is all just carbon and there's no missing metal.

Git to scraping and see what you got once it's down to metal.

[Rich82GS750TZ]

Get a dental pick and start scraping the carbon out till you can get behind that remaining gasket and pull it out.

[Forden]

Thanks all but there is no remaining gasket material, and there is really no question about the pitting (it's easy to feel that this is not buildup but absence of material). Pics are a little deceiving I think--wear marks on the gasket seat make it look like there is a gasket there. I measured to the remaining face at the bottom (below the worst of the pitting) and it matches the other cylinders. Below pic is a little better after a quick solvent / scotch brite wipe.

I will say that this bike was a rescue from many years under a deck (by a PO), and could just be a weird corrosion hangover from that. And not the result of a running issue. That might be more comforting, since the missing material wouldn't be unaccounted for, but was corroded and came out during the removal of the exhaust when the bike was "exhumed."

IMG_2462 by Forden Photography, on Flickr

I'm gonna reinstall the exhaust with new gaskets and hope it doesn't leak, I guess. At least the face is intact around the outside, where the gasket sits.

[zuluwiz]

What does the inside of the pipe look like? I'd wonder if maybe there might have been a fuel additive working, or some such, but.......just in one cylinder is really strange. How does that port compare to the others? What SHOULD it look like? It looks.....constricted. Almost like it had been filled in with epoxy (or something similar) at some point. Sure glad that's noy my problem to try to solve.

[Longitudinal]

I think you have enough to seal on there. You're probably looking at shorter gasket life on that cylinder, but they are cheap and not difficult to replace.

If it bothers you a lot, there are epoxies that are suitable for filling ports. With the head off, the port could also be welded up and ground smooth.

[Forden]

The other cylinders look fine, it's a puzzler. I'm optimistic it will seal with what's there too, though an eagle eye might note some damage to the threads upper left, which complicates that a bit--I *think I've got a decent bite on what's there, but want to chase them with a thread chasing tap before trying to torque down. Can insert a helicoil if necessary, but it would be nice not to need it...
Thanks everyone.

[rphillips]

Just a thought, what about proper sized studs in place of those bolts. Lot less chance of cross threading while installing, Half the chance of twisting off bolt when removing, plus the collars will just hang on the stud when installing instead of having to hold them up while getting the bolts started...Works way better for me.

[bwringer]

Yeah, many of us install studs. I've seen a Napa part number for a set of 8mm studs intended for a VW or something like that, but I have no idea what that number is.

[Forden]

I like that idea, hadn't considered it. Thanks. It'll have to wait until next time, as I went ahead and installed the exhaust last night.