When I hear of owners having head gasket failure after recently replacing a head gasket, I usually put it down to a number of possible causes.

Assuming that the heads and block are flat, these could be:

1)  Using poor quality gaskets. There is some real horrors out there. The only ones I would recommend are:

    Honda OEM (Obviously, but these can be expensive)

    Athena. Made in Italy, this is usually my choice.

    Vesrah. Made in Japan and of roughly the same quality and price as the Athena.

2) Failure to grease both the threads of the bolts AND under the heads with Moly grease. This is SO important. Dry threads or heads will cause friction such that you have no chance of getting the right torque on them.

3) Failure to tighten the head bolts in the correct order, incrementally, to the final torque figure of 45 ft/lbs.

But there may be another possible cause.

I'm rebuilding a GL1000 engine that has done high miles and been misused and abused by previous owners.

As I always do on a rebuild, I run a tap down the threads of each and every bolt hole to make sure that the threads are ok and to clear out the years of accumulated muck in the bottom of the holes that can prevent a bolt fully tightening.

When I came to do the head bolt holes, I was surprised to find how very tight they were on the tap. Cleaning out bolt holes does not usually result in removing much, if any, metal.  A tap down these head bolt holes did result in some metal removal; not much, but more than enough to make a difference.

This tightness would have the same result as not greasing; the final torque figure that would be shown would not have been anywhere near what it should be.

So, before you have a problem and blame the gaskets, buy yourself a 10 x 1.25mm plug/final tap and clean out those holes!