Resurfacing cylinder block andh ead

[jhillier449]

I'm going to give the used cylinder head and block a little surface mill in my CNC machine at work.

It will remove the old gasket and remove any imperfections so as to give me a good mating surface for the new gasket.

Would removing a few thou cause any issues? Will the valve piston clearance still be ok?

1980 GS1000G

Cheers

John

[rapidray]

Ten thou or less removed will give you no problems. Ray.

[jhillier449]

Thanks Ray, I was hoping to hear from you.

Cheers

John

[chuck hahn]

Touch off the chipper and then "just enough" to get it fresh all the way across.

[Nessism]

I don't think you need clean metal all the way across, just around each hole, the cam chain tunnel, and around each stud hole. There is often corrosion under the gasket, and milling the head to remove all these marks means quite a bit more cutting than is necessary to have a proper head seal.

Photo below shows a head I had milled. Machinist guy said the marks are of no significance and talked me out of wanting to cut it further.

[chuck hahn]

Ed..Is that just "marks from the old gasket or is there some pitting? How much more would have been neeed to get it finished all the way..another .005 or so?

[Dogma]

I don't think you need clean metal all the way across, just around each hole, the cam chain tunnel, and around each stud hole. There is often corrosion under the gasket, and milling the head to remove all these marks means quite a bit more cutting than is necessary to have a proper head seal.

...

I'll second that and go a little further. The only stud holes that need to be cleaned up fully around them are the two at the back corners where the oil comes through. Even there you have a little breathing room if your gasket kit has o-rings there (I think they all do). The band around each cylinder that needs to clean up isn't very wide. If you look at the head gasket, there will be a ring of exposed metal around each bore, and that's all that seals the combustion gasses. The rest is there just to support the head. I had similar marks on my 850's head, only more widespread. Pearson gave it a clean bill of health after doing nothing more to it than repairing some tapped holes and showing me how to clean the old gasket off with a green Roloc wheel.

In fact, I'd recommend cleaning the gasket off with the Roloc wheel first, then see if you need to mill it at all.