'20 RXB250L - NC250 Motor Swap [Build Thread]

[Ursa_Adv]

In June 2020 I purchased an Orion RXB250L (223cc) from Orion Powersports. Beyond a few small issues, I've had a great time putting 2k miles on my little air-cooled dual sport.





I spent most of 2020 and 2021 making modifications to the lovable little CRF230 clone. If anyone cares, a full run down can be found on my instagram:

Ursa_Adv

Fast forward to 2021 and the announcement from Orion that a new frame & engine design would be used on the '21 model RXBs. Needless to say, I was extremely jealous of extra cc's, counter balancer, and sixth gear. I had seen Jack of All Master of None's Loncin RE250 (LX166FMM-3) swap, but not gonna lie....I wanted something more.

I looked at doing the Loncin swap with an Athena big bore and maybe an oil cooler. In the end however I kept coming back to wanting to do something more.

After hours of pouring over Orion documentation and my own bike, I came to realization. The '20 RXB250 is a rebranded X-Moto XB-39. But Orion put an air-cooled 223cc motor in it. That isn't what the X-Moto XB-39 comes with stock. Queue the google translate and some internet sleuthing and I discovered the answer to my swap problem.

The X-Moto XB-39 can come from the factory with 3 different engines. One of which is the NC250 ZS177MM commonly found on things like the SSR250/300, GPX250, and CSC RX-3.

Double checking all my measurements, knowing this would not be a cheap mistake if I got it wrong, I had a few adult beverages to think it over. About an hour later, I threw caution to the wind and pulled the trigger on an engine.

https://www.alibaba.com/product-deta...7bc23e5fICGgsj

Less than two weeks and 1k later, 88lbs of Zongshen 250 showed up on my doorstep.





This thread is going to my experiences swapping the NC250 into the XB-39 frame and, hopefully, provide a sign post for other bored lunatics who decide to go down this path.

[Ursa_Adv]

I should have taken a picture of the box before I opened it up, but it was pretty well packaged. The engine was in a plastic bag with a Styrofoam shell around it, inside a carboard box, and then wrapped with packing wire at intervals along the box. This was then wrapped in some thick packing tape. I can't complain about packaging. I was unable to find any indication of damage due to packaging or lack there of.

Only complaint I have is that I now have styrofoam on everything that I have to remove. All airways and opening into the engine were covered in silver reflective tape.


Contents of the Engine (and engine kit):

Engine/Trans:
- NC250 249cc motor (engine code: ZS177MM)
- 14 tooth front sprocket
- Kick starter lever (anodized red aluminum)
- gear shift lever (anodized red aluminum)

Fuel:
- Maikuni 34mm PWK Carb
- Fuel lines

Cooling:
- x2 Aluminum Radiators
- coolant houses and clamps

Electronics:
- Engine Harness. Note: Harness appears to be from a dirt bike, not a "dual sport". may have to splice in existing lights and indicators later.
- Rectifier
- CDI box
- Starter Solenoid

In order to make sure I can adapt my current setup to this new engine I ordered the following from CSC Motorcyles:

- RX3 Clutch Cable
- RX3 Throttle Cable





Note: Please ignore my messy as hell workbench.

[buzz]

sounds like alot of work,hope it works for you. like to hear more about this build.

[Ursa_Adv]

Originally Posted by buzz

sounds like alot of work,hope it works for you. like to hear more about this build.

I will do my best to keep this thread updated. Might be a few days between posts, but I'll try to keep the flow going.

I'll have a pretty massive photo dump in the next few days. Just need to find an image host that will actually show the pictures. Google Drive doesn't play nice with inline posting in forums for whatever reason.

[buzz]

Thanks looks good

[China Rider 27]

Awesome! I have had some thoughts myself about the need for sustainable power increases the cost versus the reward. A good documented thread will be invaluable. NC strong! Ride Hard!

[2LZ]

I'll be watching thhis one!
The RX3 is fuel injected. I hope the throttle cable will hook up to the Mikuni carb.

[Ursa_Adv]

Originally Posted by 2LZ

I'll be watching thhis one!
The RX3 is fuel injected. I hope the throttle cable will hook up to the Mikuni carb.

You are absolutely right on this one. The CSC RX-3 does have fuel injection, but I couldn't find any difference between the fuel injected throttle cable and the carb'd version of the same bike they got overseas. I am working with a friend of mine to try to get one of the carb'd throttle cables to compare them.

I also have an SSR SR250 throttle cable on the way just in case. A back-up to the back-up plan.

After this is all said and done I will put together a "Needed parts list" for the swap. That way people can know what they need going into this project instead of having to do all this guess and check.

[Ursa_Adv]

Today is going to be a pretty boring day. I'll be removing and labelling the old wiring harness (just in case this all goes wrong and I need to re-install the 223cc).

I'll post up some photos tonight of my progress.

[Ursa_Adv]

I removed and labelled the stock Orion wiring harness this afternoon/evening.

The first image is the harness about halfway disconnected and the second is with it fully removed from the bike.








This last image you will see the old harness (TOP) and the NC250 harness (BOTTOM). As you can see we have some major differences right away. Length alone is going to be a problem. Also, this clearly came from a dirt bike not a dual sport. I can see a bit of wire work in my future as this project progresses.





We are going to set that aside for the time being and focus on the main elephant in the room. The engine. I am going to try to spend tomorrow moving the old engine out of the frame. More pictures and info to follow.

[herbie]

Man, I love threads like this!

[China Rider 27]

Great posts! Just a suggestion. I see you are using IMGbb for uploading pictures. If uploaded with the " “BB code full linked” you can click on them and they open in another window, click again and gives you full resolution and another click will zoom in. Fantastic function for seeing small detail in a picture. I wanted to see how the frame was put together and the carb orientation with that zoom function I could see some more detail. It would add something to the analysis so I thought I would make the suggestion.

[zero_dgz]

Originally Posted by Ursa_Adv

I am going to try to spend tomorrow moving the old engine out of the frame. More pictures and info to follow.

You, sir, are a nut. I approve of all of this.


If I ever blow up my Orion, I know what my next step will be!

[Ursa_Adv]

Originally Posted by China Rider 27

Great posts! Just a suggestion. I see you are using IMGbb for uploading pictures. If uploaded with the " “BB code full linked” you can click on them and they open in another window, click again and gives you full resolution and another click will zoom in. Fantastic function for seeing small detail in a picture. I wanted to see how the frame was put together and the carb orientation with that zoom function I could see some more detail. It would add something to the analysis so I thought I would make the suggestion.

I'll try that with the pictures from tonight. I'll make sure to snag a few of the frame. Is there any specific points you want to see?

I also try to get another light out there so I don't have to rely on the flash as much.

[Plump Kibbles]

Man that gas tank looks awesome - I wonder if it would fit my X-Pro CRF clone! I want a bigger tank but have no idea what fits.. rocking a 1.5gal I believe.

Awesome build man! I'm going to keep up with this, I may get some ideas!