Hello; I have been using four strokes since '92, Saito and OS mostly, with a few Enya's in there too. I would advise anyone to choose four strokes over two strokes. Once you are over the "familiarise-ation" phase it's all fun. Tuning is no more difficult, and once they are set, you don't have to monkey with them from season to season. I would choose a Saito 50 for your Kadet Senior, or if it's a Senorita I would choose an OS 26. Although I have no experience with Magnum (or any of the chinese brands) I have heard a lot of praise from owners of them, and I wouldn't be afraid to try one.