Shineray X1 performance problems (xy-150-11a)

[VroomVroom]

Recently clocked up two long distance trips on my Shineray. (Totalling 7,000km). Including lots of horrendous roads, 4750m mountain passes and long straight roads.
Very happy with it so far, no major problems, but I think its time for a really good maintenance. The local mechanics (I live in China) don't seem to care unless their is a big problem with the bike. Deciding to undertake the maintenance myself. Currently I have these issues:

- Front brake pulsating at slow speeds
- Chain keeps stretching far too much resulting in rough gear changes (chain is new, sprockets aren't)
- Gear ratios are far too short for long distance
- Black smoke from exhaust at very high RPM's (I guess the carb needs cleaning)
- Bike stalls every 20-60minutes randomly. Easy to start up again.
- Battery needs replacing (2years, no change)
- Headlight needs change (I'm not sure which type to replace it with, I can't find this information anywhere) H2/H1??
- Slightly stiff steering at slow speeds (compared to another bike I drove)


I recently rented a Kawasaki 150 and was suprised at how well it ran compared to my bike. Smoother engine, a lot more power, better gear ratios and less vibration all around.
Get what you pay for I guess. Anyone got any recommendations on maintenance for the Shineray X1? I have a few months with lots of spare time so planning to spend a bit of time on it.


EDIT: Does anyone know what this a copy of? The repair manual included is in Chinese and need to get an English shop manual
Thanks.