I have a toilet fitted with dual-flush operated by a large button mounted on the lid, with a smaller button inset. The unit is not cable operated and the only identification is "NF" moulded into the top. Water level is good, no problem there. I can't see anything in the projects, or by searching the forum, which helps.
It's a tall plastic thing with a vertical sliding rod (click-stops) on the back, click-stop adjustable for the lid height setting and an associated curved rod to adjust the amount by which the valve projects at the bottom. There is a click-stopped cover on the front to vary the entry hole for water into the body of the thing.
I've had two or three plumbers trying to get this thing to work, all they seem able to achieve is for it to give a main flush lasting as long as the short one. The latest has been here today, he's replaced it with a new one which is identical. I'm assured that there are no setting-up instructions, which seems very odd.
I stripped the old one to see what could be learned. Not enough! I can see how the short flush works, albeit it only just works as the lever at the back can't be very buoyant. I understand the full-flush mechanism. I cannot decide why it needs an adjustable opening or what effect it might have, and the floats don't appear to leak at all.
It ought to work! Two other toilets in the house are fine, all were replaced after leakage problems. The obvious thing to do would be to investigate one of the others but it all looks so touchy that I'm loth to disturb them!
All advice would be very gratefully received -