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1980 GS850GT top end rebuild - head machining

T

Totallyforked

Forum Newbie
Hi all,
I'm in the process of replacing the pistons and rings in my 1980 GS850. I found the surface of the head where it joins to the cylinders is pitted. It is only very slight, but easy to see (photo attached). Can someone tell me if I need to have it machined? The old head gasket still attached to the cylinders looks to be quite thick. I saw a YouTube video of the same model and saw that the surface of the head on that bike looked pitted as well and he reassembled the engine without machining. I considered that maybe this is a common feature of the GS850 and that machining might be a bit over the top?
Also, there are scratches on the dome of the combustion chamber where it looks like someone has tried to remove the old carbon with a sharp auger. Hopefully this can be seen in cylinders 1 & 2 in the photo. Is it important that this surface be totally smooth and scratch free?
Any help would be appreciated.

cylinder head.jpg



​
 
I think the head gasket surface is okay. The rings around the cylinders, cam chain tunnel, and oil passages looks clean, which are the critical sealing areas.
 
Just get it machined, those graphite head gaskets make a mess and are nearly impossible to fully remove without damaging the gasket surface. What ever you do do not sand or use rotary abrasive wheels to clean the surface. You new head gasket will likely be a metal layer gasket and those don't like rough surfaces.
 
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