Wheres the link to the actual page you bought your bike from?
edit, found it on page 1
anyways,
Looking here,
http://www.atvdiscounter.com/Dirt-Bi...oductInfo.aspx
You will see pictures of the balanced engine, but it does not say it has it, in fact it says
# Engine Type:Single-cylinder,air-cooled,four-stroke
# Engine model: 163FML-2
Which is the non-balanced version...
Of course, I don't know what the ad you got it from actually said, and either way they are trying to screw you...
edit 2:
looking at the ad more closely (your ebay ad)
It also states the same details about the engine
# Engine Type:Single-cylinder,air-cooled,four-stroke
# Engine model: 163FML-2
Which is non balanced, however they are using pictures of the balanced engine...
Also they said you were getting a gy5 and you got a gy2,
smaller gas tank
lower seat height
I'm not sure what else
I highly doubt they are an "authorized american lifan dealer" like you said you saw somewhere though... I don't know where they told you that, but I bet if you check with american lifan you will soon find out it was a lie, I think they might be interested to find out that they were claiming to be... Unless you just got that impression from the swing arm decal or something, I believe all the US lifans will say american lifan on them if they came from Chingqing, I believe it has to do with how C.L. exports them...