Made by Nicot and distributed by Orion, the RXB has a very KTM "inspired" frame design with a Honda CB derived single cylinder 249cc engine. A lot of Chinese drop-shipped bikes are advertised as "250" cc, but this one actually is. It's got six gears, too. Capable of 20-ish horsepower, lightweight, simple, cheap, it's about 75% of a KLX250 or CRF250L for 25% of the price. Mine is one revision older than the one they're selling now -- the current version has fuel injection. Mine is a carb.
Somehow, my local DMV tried to give me shit for the relatively tame Shinko 805's on my KLR, but this thing and its tires sailed right through and they let me slap a plate on it. Go figure. (The stock ones it came with weren't even DOT. I replaced the rear with a Tusk DSport after burning it up pretty much immediately.)
I guess because it’s a CB 250 derived engine it should be pretty reliable?
It certainly seems so. Lots of the ancillary bits and bobs on Chinese bikes are of questionable quality, but one thing the Chinese are damn good as is stamping out Honda engine clones. They've been doing it for decades. The engines in these detuned to make them very low-stress; they'll run just about forever and are designed to do so with little to no maintenance. Despite what "everyone knows," parts for these engines are actually incredibly easy to find, and they're dead simple to work on if you ever have to. In a given engine pattern coming out of China, the parts are all interchangeable. So trying to search by make/model/year is a fool's errand, but just looking up your engine type will allow you to import any component you need from Amazon/eBay/Alibaba/whatever.
The engine in this one is made by Zongshen, usually regarded as one of the better manufacturers in the PRC. Engine model code ZS172FMM-5, which is a 249cc overhead cam, with 6 speed transmission. If you manage to blow it up, you can buy this same engine as a fully assembled crate motor for about $370. Another popular engine pattern is the pushrod single cylinder CG motor, as found in the RPS Hawk and its various derivatives. Also tons and tons of GY6 clones, in every displacement you can think of.
I haven't had any problems with this bike that I didn't cause myself... I did manage to knock the exhaust off once on the MABDR, which turned into an entertaining experience when it hit my rear brake line on the way down and melted it. Riding home 250+ miles, much of it off road, with no rear brake was an experience. I lived to tell the tale.
Here's the little bastard, plus my buddy and his KLR, at an overlook in Bald Eagle on the MABDR in Pennsylvania: