Quality in motor production for the Chinese 2 strokes are more or less the same. Which is inconsistant. However, some do have greater customer service than others as I have been told. Read through some of the reviews and decide.
I got 2 from BoyGoFast and 1 from PowerKing, both on eBay. They have all been working great. I have ridden 1k, 300, and 100 miles respectively on these motors. So I haven't really need to talk to them.