Das war die Antwort von Trevor:
If I were building the engine for myself I would run the 4 bolt top end. The zenoah cylinders last longer and are far less likely to crack, in addition the port layout is symmetrical so it makes a little more power. Modifying the two bolt case to work with the new 4 bolt cylinder is fairly simple, if you would like to know how email me for instructions.
Thanks,
Trevor
Und nu abwarten was auf meine Antwort zurück kommt....
fairly simple... also geh ich davon aus, das es kein hexenwerk wird