One problem is gone another one is back
I changed the oil again and this time used thinner 10/30 gear oil (Motul).
After a longer ride yesterday the dragging problem is completely gone, except when the engine is stone cold. I really can live with that.
Unfortunately the squealing is back even when the clutch is only slightly abused. So I invested in a new Rekluse clutch basket, new steel and friction plates, a new slave cylinder plus a repair kit for the master, new oil all together for USD 590.- where I live and still no joy.
I think the time has come for the GasGas and I am sad as it was a brilliant bike but I have reached the point.....