I have a recently arrived Soennecken which will allow only very short piston travel, about the length of the ink window or less. Taking it apart, the piston mechanism uses a key on the piston running in a recessed keyway inside the barrel. Examining inside the barrel, I could see that the plastic is slightly fractured on the clockwise (from the back) edge of the keyway. What happens is that the piston draws up then the key enters the fractured section to the side, under torque from the piston knob, and jams there having no further straight path up. A bit like a train accidentally diverting to a siding with no exit route.
The first obvious possibility is to rebuild the fractured section, perhaps with an epoxy. The difficulty will be to keep the barrel concentric and to shape the edge sharply. Fiddling around a couple of centimetres down an 8.5 mm barrel, I am not confident of that being a great success, if there is a better resort.
Has anyone experience of this type of repair? What worked?
I could ask the vendor for money back on the pen sold as already restored (they replaced the cork seal). I prefer to make things work if I can.