I'm glad the YBR's worked out, please keep us posted on the modifications and general maintenance you are doing to keep them running. Since you are hitting the hard stuff with them, I think a lot of people will be interested to know how they hold up in the long run.
+1

I'm still thinking about buying this bike....just the cost. 25,000 yuan for a single cylinder commuter bike with a rear drum is a bit expensive. But if it can really take serious long term abuse, then maybe it is worth the cost, or if a 2nd hand or bulk buy is possible, then even more maybe.