I've been riding my pk50 for quite some years now.
19/19 polini 90 jet
125cc gear ratio
It runs fine, the only thing that keeps bothering me is that the carb spills quite a lot of petrol out of the air filter housing. I've just ordered a new air filter. It is a polini air filter (Art.Nr. 20300190). This later version aparently has a new inner ring. The jet is quite big I know but it's the only size on which it runs good. Is the carter pressure to hight maybe so it blow's back some of the intaken fuel? Maybe I can run with a smaller jet with the new housing but something tells me that is not the origen of the problem.