Fork problem

[unfazed]

Any suspension technical Gurus out there who can answer this as it seems to defy the laws of physics
I have spent many years setting up supension for friends to suit the Irish roads "Gixers, R1s, S1000RRs, Fazers and recently an RSV" (even the mighty S1000rr on standard suspension setting can be embarassed by a 600 fazer on Irish twisties), but one thing with the 600  fazer, my own included which baffles me is this.  :eek
The right fork leg presurises over a period of time to such an extent it effects the static sag. I have not noticed it on the other bikes I have set up. When you open the fork cap air gushes out. All the seals were fine with no leaks. I first noticed it when I could not set the static sag on my own a good many years ago and noticed it on 2 other Fazers since including the 400 recently (I had installed the preload adjusters on the 400 when I fitted Progressive springs). Here is the strange thing, after my altercation with a bus a few years back I "missaligned" :lol one of the forks legs and  replaced both the legs and seals and now it does not happen.
My question is how in the hell is the air getting in?  :wall
I asked the lads in Hagon when I first noticed it and they were also mystified.
Maybe it is the reason for the question on the  post about the "right fork leg seal"

[Fazerider]

Interesting.
Not something I'd noticed with mine, and neither has my right fork leg shown any preference for leaking as compared with the left.
I suppose there are three possibilities.
The oil is somehow breaking up into small enough molecules to become gases. Possible in the presence of suitable catalysts and steam or hydrogen at many hundreds of degrees, not too likely to happen in a fork leg.
There's water in there forming oxides of aluminium and hydrogen as it rots the insides. I'd be surprised if it could generate enough to be noticeable, but you could at least test for it (and the previous idea) by seeing if the gas is flammable as you release the fork cap. :eek
Alternatively, air is getting sucked in past the fork seals each time the fork extends. Which sounds like damaged seals... in one direction.

[Dead Eye]

Can't say I noticed this on either of my fork sets. Granted one set was slightly roasted

But the other ones have 88k miles on them and by the looks of the internals had probably never been serviced before :| Neither set had any pressurisation...

[Paul]

Only ever changed the fork oil once, but neither of the fork legs were pressurised.
I assume its a release of gas, as oppose to air being sucked in?

[69oldskool]

Do you do a lot more RH bends than LH'rs?