Many have wrestled with this question over the eons of bike days
Right off the bat, from my testing if you have any other options the answer is no.
Copper head gaskets are much harder to get and maintain a good seal with than with fiber or Multi Layer Steel (MLS my favorite).
But there are times when nothing else will do.
I have been testing and tuning a 86-88 KX500 top end.
I was trying to dial in the best compression ratio.
Generally, the easiest way is to swap head gaskets for various different thicknesses.
So first, I took a copper head gasket out of the package and tried it.
It leaked like a sieve, inside and outside.
Next, I tried to anneal or soften the gasket by heating it up with my map gas torch and used a sealant.
It did not leak externally, but was definitely leaking internally as evidenced by the white smoke coming from the exhaust.
Last, I went to a buddies house and he used his Rose Bud tipped torch and got the gasket cherry red.
Then, tossed it into water...
Yes, water...
Copper reacts different to water quenching than steel does.
It does not get hard by quenching.
Next I had to clean the gasket as it leaves a residue on it that you DO NOT want on it.
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To clean it, I used a light machine oil and the grey (Very fine) scotch brite.
When cleaned it looks like this.
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Notice the pitting?
This is very common.
Using the Copper Coat Gasket Compound fills in all the minor imperfections and helps it seal.
I coated both sides of the gasket with the sealant.
I waited until it dries... approx 3-5 minutes, then I installed it.
I used a cross hatch pattern and went 10lb then 15lb and finally 19lb torque specs.
My plan is to run the bike till warm, shut it off and torque again.
No leaks.
However, I have been told that they always nearly always leak over time.
So again, I would not recommend a copper head gasket for long term usage.
But sometimes you just gotta scratch that itch
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