Screwed up
 

doh doh

https://i.imgur.com/VfLGwV2.jpg

Wanted to remove a dowl pin so used my vice grip to rotate it lose. Well apparently a hard, sharp edge of the vice grip was touching the head surface and it produced quite a scratch. Possible the worst location to do this doh

How screwed am I? I just re-did the entire head, lapsed the valves etc. :mad2:

Maybe the head gasket + a little gasket sealant will prevent a leak?
Won't be able to do a pressure test for a while...

doh

If you wanted to be super cautious you could get it skimmed but I would put it back together using just the head gasket and see what happens, you will be surprised at what you can get away with sometimes.

I did similar on the face between head/ rocker cover although was deeper than yours. Used some JB weld to fill gouge and has been ok and sealing well. I would clean any protrusions with a smooth file. Maybe some JB weld if it is deep enough but it does look very shallow. The gouge looks deepest where it doesnt really matter anyway?

Except, unlike the head/rocker, the part where I scratched is the barrel/head which is responsible for keeping all piston compression :(.

My only luck is that it isn't all the way till the end, but only just. Won't know until engine is in the bike and I can do a compression test.
Don't think it's deep enough for JB weld but there's definitely a small groove that is very noticeable with the finger.

the only sealant that can be used in the head is cooper paste/spray,


dont even think about silicons or anaerobic sealant, nothing will stand the heat


but cant see the problem to remove the valves and do a minimal skim, just note down where each valve is.... not costly either.

Sealant I have is rated up to 250c.
All my local garages have waiting times unfortunately, and it will definitely be 30min-1hour so at least €50.
I think I'm gonna try my luck.

disagree with using sealant, even 250 C sealant, but it's your bike at the end :)

Obviously I'm not replacing the OEM gasket with sealant. This is the idea:

https://i.imgur.com/6Tjk0Ip.jpg

https://i.imgur.com/E1PzLgD.jpg

https://i.imgur.com/DPuvcik.jpg

Looking at the last pic, I think it will be fine?

of course I didnt think you'd omit the gasket.... still, would not put that blue stuff,

Hm.. you think it will do more harm than good?

Not sure how copper grease would help.

JB weld? If possible with this size... Or just try it with OEM gasket only?

IMO based on what you say [ a small groove that is very noticeable with the finger.] which runs through the flame ring part of the head gasket, I think it should be machined/skimmed.

Bob

copper paste is essentially fine metal particles suspended in grease. when it is pressed the little particles fill small gaps and the grease evaporates with temp. that's the only thing ill ever use in a head gasket, otherwise I go dry.



it's an odd situation, hard to predict, maybe all will be good without adding anything maybe not.

Well like I said my only luck is that it doesn't go all the way to the edge, so from the inside of the cylinder you don't see anything and in theory it should seal.
I'm just afraid that the gasket will start warping or failing at this spot or something.
I think i'll just do a compression test when the engine is together and hope for the best...

So today I decided to do a compression test (finally got a 12mm adapter one) to know once and for all how much I screwed up.
Result:
135 PSI cold
145 PSI warm

New from factory: 154 PSI

What do guys think? Is it good enough? Engine is running fine so far.
I never tested this engine/head so it might be because something else.. e.g. my valve-lapping skills.

It's fine! the numbers are reasonably good, and I assume there's no sign of a leak or hot gasses coming out at the point where the scratch is, so don't worry about it, be happy. :)