I have one of these YG250-NF's, and so far, dealing with Yingang is quite pleasant. It's not a cheap piece of crap, it's also not of comparable quality to a Japanese bike. I would put it somewhere in the middle. If you pay $2495, and your looking for a fun little bike to blast around town, you probably
won't be disappointed. If you drop your life savings on it, thinking you're getting more value than a good used Japanese machine, you probably
will be disappointed. I was looking for an inexpensive bike to get me back and forth to work, I have other motorcycles for dirt riding and adventure touring, so the Yingang will do fine for the 15,000 kilometers of commuting I do every year. It will also save a lot of wear and tear on my other bikes, and the 70MPG fuel consumption won't hurt either.
Maybe some time perusing NX250 / AX-1 forums, and a bit of ingenuity at the local bike salvage yard or eBay, will fix the carb and air-box issues. Any performance info you find on the Shineray X2 will also apply to this motor.
If I wasn't living in China, would I buy this bike? Maybe... that would depend on the level of dealer/distributor support that comes with it, or how good you are at working on bikes. I also wouldn't consider it a good bike for big people. I'm 5'9" 160lbs and it's OK, but larger people would be very cramped.
I can say with some confidence that Yingang in China is much better than many of the other companies here when it comes to certifications and customer service. They seem to be trying hard to get it right.
This is my first post on China Riders... I usually post on the "other" China motorcycle forum, but I do lurk here from time to time so I thought it good to give something back.
Cheers!
ChinaV