I recently bought a used HKS SSQV 1 from Ebay. When I installed it in my car, the valve didn't open at all. I took the whole thing apart and think I found the solution, and I hope that i can help you with this.
First of all, the HKS SSQV is a pull-type Blow Off Valve, which means that the valve is closed by the boost pressure and has to be opend by vacuum force.
During boost, the small valve which looks like a nut is supposed to let some pressure in the area between the boost area and the area where the vacuum line is connected. This valve has also a small bypass (very small hole on the valve).If the throttle body is closed,the valve should normally let the overpressure in the middle part of the valve very slowly escape thru the small bypass hole, not the main 4 holes (the valve is mainly a 1-way valve with a bypass). The pressure difference will suck the piston more to the vacuum site, which opens the valve.
In my case, this valve was letting the air in the middle part escape to the vacuum site even more easily than in the other direction, which caused the valve to not open.
To fix this problem, I used some hot glue to clog up some of the main 4 holes (I closed every hole but you have to try what works for you the best, for me this works perfect).
The best solution for this would be to buy a new 1-way valve, but I haven't found one.
To take the valve apart, you have to remove the 4 bolts on the front of the valve which look like they are "deeper in the valve", the other 4 unscrew not the cover, just the gasket of the valve which is not neccesary. Next, remove the 8 bolts and nuts on the back. You should now be able to open the valve and see the valve.
Now remove the spring and the cap on it. When applying hot glue tho the valve, make sure you don't clog up the small bypass hole. When you have done this, put the valve back together and try it.
I am not sure if this will work also on the other versions of the SSQV, because I haven't disassembled them and they also have also no adjust screw.
I hope I could help you
