'20 RXB250L - NC250 Motor Swap [Build Thread]

[Ursa_Adv]

I went back and re-worked the front brake master cylinder and brake line. Switched to a bigger master (Honda TRX) and a 130mm line. Much firmer. All around cleaner. Also: GREEN

[Ursa_Adv]

Went for my first test ride today. No footage. Just went up the block. Tooled around in a parking lot for a bit but: I am 100% satisfied with my handy work.

It is super smooth. Counter balancer on this thing is no joke. Acceleration and throttle response are what you expect from a true 250 single cam. Electrics worked and didn’t catch fire (always a plus). Rear brake needs a bit of a bleed (may have forgotten to do that).

Key takeaways:
1) It runs, drives, shifts, etc.
2) zero sounds that make even the most seasoned tinkerer wince
3) I managed to not DNF this swap

[Ursa_Adv]

Installed one of these:

https://www.rockymountainatvmc.com/p...it-universal-p

As I was not looking forward summers without a fan.

Working on the tach today, but fingers crossed she'll be in her final form by the weekend.


Also...IRL stuff happened. Laid off. Moving. Etc. Nothing anyone cares about, but I'm in a good place and moving somewhere I actually want to be.

[Ursa_Adv]

I took my first extended ride yesterday. I noticed a few things:

1) Gauge cluster sits too far out and is making the headlight sit all jacked up. Fixed.
2) My wheel circumference is set incorrectly in the speedo settings. Reads about 20MPH under my actual speed. Need to set the wheel size correctly.
3) One of my fans has decided to cozy up to one of the hose clamps. FIXED
4) Rear brake needs a return spring. Stock Orion didn't use one, but after swapping to a 250X rear brake master it does not bounce back like I want. I picked up a return spring from Hammerhead Moto. FIXED

Other than that, I put about an hour on the clock. Only had one stall at a stop sign and the bike feels great.

[Ursa_Adv]

The weather (fingers crossed) has broken. Engine just rolled over 100 miles after my ride yesterday. I think I can call this build a success.

I have 100% given up on this gauge cluster. I am reasonably sure the unit is bad. I have wired it six ways from Sunday. Adjusted all the settings and sensors. I can't get a good speed reading or Tach. It's either 0 or 199 MPH with one magnet. Reads about 20MPH under actual speed with two magnets. Tach hasn't moved since day one.

I sat down and priced it out for a like Voyager or Voyager Pro. Not interested in spending that much. I priced out the smaller unites (Endurance or Vapor), I am not super impressed by them or dealing with more wheel sensors.

I happened across a random youtube video of someone using an old Garmin as a GPS/Speedo and building a little bracket for indicator lights (headlight, turn signals, etc). I am on board with this as I wanted to get a GPS unit setup going anyway.

I'll post some pictures up as I build out the brackets.


Running list of tasks:

1) Build bracket to mount GPS unit behind the headlight but in front of the bars without blocking the key.
2) Front wheel has a little wobble above 50 (assumed) MPH. I think the Wheel bearings are going out. They're the stock ones and probably not the best quality. Could be the tire treads too (Trailmax mission). I'll probably pop it off to check the spin and trueness in the near future.

[Ursa_Adv]

RAM mount is in place for the Nuvi 1490T. I have to say I like the look. It fits behind the windscreen rather nicely. At the moment I am deciding if I want to put my indicator LEDs off to the right (Gear indicator, blinkers, and headlight) or on top (Neutral only, blinkers, and headlight.

[Ursa_Adv]

I made a quick mock up with some plexiglass and a few indicator LEDs. Will probably make a second from ABS plastic or just a “cleaner” one with the left over plexi.




I also swapped out the chain guide for a new one. I hacked it up pretty bad back when I installed the Warp9 rear wheel. It was long past due for replacement. Had to put another hole in the bracket because of course it wasn’t an exact drop in.

[Ursa_Adv]

Built some rad guards out of steel gutter guards. Took a grand total of 15 minutes, a pair of wire snips, and some sip ties. Thanks Ace Hardware. $ 4.99 well spent.

[Ursa_Adv]

Finished the new dash (mk II). Moved the indicator lights to the left of the GPS unit to keep it further beneath the windscreen and to leave the ignition key clear. Put another 50 or so miles on during a spat of nice weather we had.



Next big milestones will be the first oil change and suspension upgrades (weight has increased significantly since stock configuration).

I’ll keep everyone posted.

[Ursa_Adv]

So at this point the build is complete. I'll post up some running footage of the bike out on the road, but we're just into general tinkering at this point. The "meat and potatoes" of the build are done.

It's been fun, but now its just time to ride this beast. I'll periodically update this thread as new things crop up (post first oil change, catastrophic engine failure, etc).

[Ursa_Adv]

Back after a long summer. Just completed the 500 mile break in of the engine. Oil change went by with relative ease.

I had swapped oil that came in it for Honda GN4 10W40 before installing the engine. It was decently dark coming out of the engine after 500 miles. The filter screens had some metal, but nothing beyond a normal break-in. It came stock with a metal oil filter, but I have swapped it out for an Otom paper filter.

Drained the engine, cleaned things up, and then sealed it back up. I used Maxima Premium 10W40 (1500ml per the manual/oil cap). Let it warm up for a few minutes. No leaks.

I called it a win and put the skid plate back on. No drama. Took me about an hour. Probably get it down to 15 minutes to a half hour next time.

Now I can start really opening it up, those upper registers of the rev range have been calling my name lately. I've got a ride out to the Oregon coast planned for next week, so a few more bits of maintenance and then its time to hit the road.

[bobswatch24]

Congratulations on your build - it looks awesome!


I'm in the process of putting an SSR 250s (Asiawing) bike back together and I'm using a 34mm Nibbi type carb.


I wondered if you had any advice on jetting? What settings did you end up at for main jet and pilot?


Many thanks!

[Ursa_Adv]

Originally Posted by bobswatch24

Congratulations on your build - it looks awesome!


I'm in the process of putting an SSR 250s (Asiawing) bike back together and I'm using a 34mm Nibbi type carb.


I wondered if you had any advice on jetting? What settings did you end up at for main jet and pilot?


Many thanks!

I started out using:

Pilot: 35
Main: 135
Needle: 2nd clip from the top

But I got the feeling it was a running a bit lean/hot. So I changed to:

Pilot: 45
Main: 150
Needle: 2nd clip from the top

I am at 283ft above sea level. So if you are at higher elevation, you may need to adjust accordingly.

[Ursa_Adv]

Originally Posted by Ursa_Adv

I started out using:

Pilot: 35
Main: 135
Needle: 2nd clip from the top

But I got the feeling it was a running a bit lean/hot. So I changed to:

Pilot: 45
Main: 150
Needle: 2nd clip from the top

I am at 283ft above sea level. So if you are at higher elevation, you may need to adjust accordingly.

Then I realized I am not as smart as I think I am and moved back to:

Pilot: 35
Main: 135
Needle: 2nd clip from the top

[Ursa_Adv]

The bike is in at the fabricator this week for exhaust ver. 3

Basically I have reached the point where to get it looking and working the way I want I need a professional. Should be back up and running for the summer season.

Went with a 2017 KTM 450 muffler I managed to snag. It fits the Orion mounting points perfectly and looks super clean. Will post pictures when she is done.