I would also recommend u the RR brand, as I'm quite happy with mine too.
I don't have any pb anymore though I had all the same as Dewsnap till around 1000km, except those linked to the cooling system as I don't have any on my 2010 version.

Thing is:

The RR 150cc is 20K in Viet Nam, so I don't think I still can recommend it.

Also, the 250 feels heavy to me: 20hp for 165kg is NOT such a good stat, I still can "throw it around" as dewsnap says, but maneuvering did turn a couple times into shameful situations, I'm 65kg.

Makes me wonder how heavy is the 150cc u're lurking at...

Check this out, asu don't want to end up missing ur Haojiang.

Also check the price for a Japanese made 125cc, as if the $ difference is low, then there's little point in getting a RR.

A japanese made 125 cc will be slightly more powerful than the RR 150cc (even if single cyl), lighter and more comfy, and sure will take the heavy rains punishment better than the RR, also will probably handle better on wet ground.

That's a lot to consider.