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No eBay APP ID and/or Cert ID defined in Kunena configurationThis is what I bought.

Fill the groove with your High Temp and ride the piss out of it. You might consider new viton valve guide seals too.
Steve

That is the opposite of what I have experienced. I used about 4 one piece head gaskets on my GPZ1100 and they all leaked from the center where the o-ring goes. I used all quality head gaskets with RTV in the o-ring groove. I tried the RTV let it cure shave it off then assemble, tired it using the RTV then assemble before letting it cure. I even tried cutting the o-ring in half laying a thing bead of RTV in the o-ring groove then placed the cut in half o-ring intot he groove then assemble with the one piece head gasket. Everytime I used a one piece head gasket no matter what I did to the o-ring groove it always leaked. And yes I did heat cycle the engine and re-torque everytime I replaced the head gasket
My ultimate solution was the use the stock two piece head gasket with an OEM O-ring all dry. That stopped the leaks

Two things come to mind I have experienced: Engine build and used Athena gasket set where all was fine for a season albeit I put up with a dribble of oil down the front between the head and the cylinders. Pulled the top end off and the peanut shaped o-ring was like a nacho chip and became 50 pieces. Discovered that after cleaning all areas around the base of the cylinder studs, different studs of the same length seemed to be projecting at different heights from the top of the cases. I tried to torque the studs down and they would not move into the cases any further. Not wanting to risk damaging the cases I bought some taller APE head nuts that would allow more travel, reheated the copper washers and reassembled everything. As the book show, add some silicone during assembly to the area around the center rear two studs. Can you believe it, no leaks whatsoever around the engine and after a couple of heat cycles and a re-torque all is still good. I will never use the aftermarket peanut o-ring and only NOS head and base gaskets when available.

I've been using the one piece head gasket for almost a year now. No leaks. The O ring has been a problem for 40 years. Sometimes it would last a couple years other not even a year. NOS, junk, aftermarket, junk. Filling the groove with high temp copper silicon solved the problem. The copper silicon it stickier than other silicon. It's all I use now.
Steve