Thanks for the tip Alec, I used some parts from a ballpoint pen.
There are some weird actions going on however. When I pull the start lever, the tonearm rises in the lock position, I hear some rubbing, then it moves to the middle of the record, it lowers and rests for about a second, then it moves back to the lock (the idle position). It does not stop at the beginning of the record and lowers itself.
It also hear the "Steuerpimpel" rubbing the lever on the inside. Is this a good sign? Or should I shorten it? It's made out of hard plastic from the inside of a ballpoint penn.
I put it on youtube to clarify:
Exterior action: http://www.youtube.com/watch?v=6-xGXJvkUNo
Interior action: http://www.youtube.com/watch?v=Uv1K833hpeE