Showa TAC... I am getting lost.

Ah the Showa TAC.... I spent many frustrating days with it on my RMZ450.

Sounds to me as if you have something quite serious going on, its normal for the main inner chamber to increase in PSI a little due to heat build up in the fork and temperature changes. But it shouldn't be that much to the point that you cant engage your holeshot device.

I would start out getting them serviced and checked out, as something doesn't sound right there.

Also make sure that you are emptying and re pressurizing the chambers in the correct sequence, as this can negatively effect the fork when done incorrectly.

Oil leaking out from the valves when emptying the chambers is normal, and quite annoying.

There are a number of people who like the TAC fork and happily run it, I got mine set up pretty well in the end although I still swapped them out for spring forks. It takes a fair amount of testing and trial and error to get these forks right. The Showa SFF TAC fork app is helpful

I have a lot of experience with this fork. Stock form it was ok. After i had it rebuilt and revalved by RaceTech, night and day better for me. Then i had the SKF glide kit installed + SKF oil and dust seals. I love these forks, and am actually sourcing a take-off set to put on my KX 125 .

What pressures are you running for your weight?

If releasing the air pressure from the fork does nothing, you either are not releasing the correct chamber, are doing something really wrong, or something is extremely wrong with your forks and you need to stop riding on them. If you dump all of the air out of the Inner chamber without touching the outer and balance chamber, the fork should collapse because the inner chamber is essentially your spring.

The proper procedure needs to be followed when setting pressures. Here is my tried and true method for consistency in the forks:
1. Put the bike on the stand so that the front wheel is off the ground.
2. Starting with the balance chamber, release the pressure down to 100psi indicated on the gauge.
3. Next, fully deplete the outer chamber.
4. Next, set the inner chamber to the desired setting (for me, 180psi)
5. Next, set the outer chamber to the desired setting (for me, 10-15psi depending on the track)
6. Next, set the outer chamber to the desired setting (for me, 190psi)
7. Next

It's normal for a tiny bit of oil to spray out when you release the air chuck. The chambers are under pressure like an aerosol can.

For your weight and height, you should be around the same pressures as me. 180 inner, 10 outer, 190 balance.

In my experience, you need to run the balance pressure equal to or more than the inner chamber pressure in order to maintain initial plushness.

Thanks for your for the replies,
Actually, I rode for 10 years on YZs with SSS forks, these forks were so good out of the box that I became a lazy fork tuner...

So.... ... I went to check the bike yesterday evening after reading your comments.

I followed your procedure Bryan and the fork is now working correctly when I push it. It pressure was anormally higher.
However I have to ride it to see if it is better,

My riding buddy who is motorcycle mechanic told me that cold weather (-5°C = 23°F in France now) can build some pressure during riding session since the heat in the fork constrast with the cold outside . He also told me to fully deplete the chambers occasionally before adjusting the pressure. I never did that before.

Next time I go ride, I will simply put the hydraulic fork tube in stock mode and the air fork accordingly to your recommendations Bryan.

I'll keep you updated, thank you again.

I had the same problem with my CRF Showa tac's.
One day at the track, they almost seized up, would barely move. I reset the pressure, but it didn't help. I packed up and went home.
I never liked the way they felt anyway, so I took them off and sent them over to Technix.
They put the SKF Glide Kit in and SKF dust and oil seals. Completely changed them, they are really quite good after that work.