hi again, the difference in the main bearings may be due to the different methods of lubrication, eg pre-mix and oil injection
and in regards to the gearbox, this differs from the main bearings in the way it is lubricated eg. by thicker gear oil.
and the different cage materials may be due to the fact that as the models developed mz had to adapt to a increasing market in western Europe that demanded better quality ?. and as oil technology improved this may have effected the choice of bearings.
One final factor to consider is the power characteristics of the engine – the etz seems to be a more “revvy” engine than the Super 5 which has more torque lower down. It may be worth asking the same question on one of the MZ racing web sites or post it on the German MZ site http://mz-forum.com/ which has an English speaking forum
keep us posted of your findings…..ian