I have recently rebuilt a P150X motor. While testdriving the Vespa, I had a cold seize. After it had cooled down, it started without any problems and I drove back to my shop. I turned the air mixture screw in by half a turn and again took it for a ride. And again I had a cold seize. (First time this has happened to me).
Now my questions are: is it the wrong air adjusting screw, or must I change a jet somewhere?