hi, i have a kyosho GXR-28 engine and the HSN on it is so loose it turns itself out whenever i run my engine, making it impossible to have a consistent tune

Your O-Rings are bad. You can order them and just take the carb apart to fix it. I recommend getting O-Rings for the entire thing, because if one is bad, the others are probably getting there. Thread Lock works as a quick fix, just don't put a ton on.

Thanks, where can I order O-rings suitable for the task

In the time you are waiting for the O-ring you can cut of a snall piece of a fuelhose to use as an O-ring.