'20 RXB250L - NC250 Motor Swap [Build Thread] - Page 2

Plump Kibbles · 10-24-2021, 02:57 PM

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!

OffRoadToad · 10-26-2021, 08:12 AM

Quote:

Originally Posted by 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!

I thought the same thing when I saw that tank. I was just looking at tanks this weekend.

You wouldn't happen to have a part # or link for that, would you Ursa?

Oh, and subbed. Great thread since I have the same bike.

Ursa_Adv · 10-26-2021, 02:51 PM

Quote:

Originally Posted by OffRoadToad

You wouldn't happen to have a part # or link for that, would you Ursa?

Oh, and subbed. Great thread since I have the same bike.

I do:

2015 KTM 250 SX
Acerbis Fuel Tank 5.3 Gallons Natural
Link to RMATVMC

OffRoadToad · 10-26-2021, 03:48 PM

Quote:

Originally Posted by Ursa_Adv

I do:

2015 KTM 250 SX
Acerbis Fuel Tank 5.3 Gallons Natural
Link to RMATVMC

you are the man! Thanks for that

Ursa_Adv · 10-25-2021, 05:19 PM

Turns out the Swingarm removal is way easier than I thought.

Loosened the bolts up last night, I'll be pulling the swingarm in its entirety this evening. Then we're on to test fitting.

Note: I'm a turd and I labelled the 21mm nut on the swingarm a "21mm bolt".

China Rider 27 · 10-25-2021, 07:11 PM

With that full resolution zoom function you can get right in there and see it. That suspension looks beefy. Adjustable for rebound? Any issues with it?

Ursa_Adv · 10-25-2021, 08:05 PM

Quote:

Originally Posted by China Rider 27

With that full resolution zoom function you can get right in there and see it. That suspension looks beefy. Adjustable for rebound? Any issues with it?

Yup. Dual adjustment on the front and rear shock.

The only "issue" I had with it was my fault. I never set my preload properly, which was fine when I was just tooling around town or some light forest roads.

However, when I started pushing the bike harder things went south quick. Needless to say I chunked a very nice tire off the muffler. No one to blame but myself on that one. Live and learn.

Other than that I can't complain. I know Dave (Dirtbike Channel Dave) and Joe Henner have made some modifications for usability, but they are strictly motocross. For the average user, the stock suspension is probably going to be fine. Heavy riders might benefit from swapping the coil out though.

Ursa_Adv · 10-27-2021, 05:02 PM

Test fit is complete. We ran into a few clearance issues. The front mounts for the motor are in the way. No matter which was you slice it, but we kinda knew that was a possibility going into it. So no real deal breaker.

The other place we had a "hit" was the stock skid plate mount under the frame which was impacting the oil drain plug on the bottom of the engine. I used what was left in my angle grinder disk to remove the mount for the skid plate.

I've got to pick up a new grinding disk and then I'll get started on the front mounts as well. At the end of the day, I need the rear mount (swingarm) to slot and align. The others, I can fab in later.

ExMxer · 10-27-2021, 10:29 PM

Tilt that engine “up” about 3-6 mm….. from the front of course. Look at it from a down the road perspective. Raise up, before grinding down…..anything. Room is above, using the swing arm as a pivotal point, don’t use the cradle as a crutch. The more you can upright that cylinder, while keeping the cases somewhat level, the better off you’ll be. Sounds dumb as shit, but it does work. Hell, go 10 mm if needed….. that cylinder has a hell of an angle ahead of it. I really admire your work progress, swaps are a real test, keep it up!

Ursa_Adv · 10-28-2021, 12:39 AM

Quote:

Originally Posted by ExMxer

Tilt that engine “up” about 3-6 mm….. from the front of course. Look at it from a down the road perspective. Raise up, before grinding down…..anything. Room is above, using the swing arm as a pivotal point, don’t use the cradle as a crutch. The more you can upright that cylinder, while keeping the cases somewhat level, the better off you’ll be. Sounds dumb as shit, but it does work. Hell, go 10 mm if needed….. that cylinder has a hell of an angle ahead of it. I really admire your work progress, swaps are a real test, keep it up!

You got it in one. The plan is to get it in the back mount (swingarm) and tilt the whole engine up.

It's only in that position in the picture because it won't sit any other way.

The front two upper mounts hit the counter-balancer just enough to keep me from tilting it up.

The end result will have the cylinder sitting more in a vertical position, but I have to clear those two front mounts.

ExMxer · 10-28-2021, 01:29 PM

Quote:

Originally Posted by Ursa_Adv

You got it in one. The plan is to get it in the back mount (swingarm) and tilt the whole engine up.

It's only in that position in the picture because it won't sit any other way.

The front two upper mounts hit the counter-balancer just enough to keep me from tilting it up.

The end result will have the cylinder sitting more in a vertical position, but I have to clear those two front mounts.

You got this! Looks like kind of fun that makes a man cuss from time to time

Seriously though, that engine looks impressive, bike should rip. Enjoying watching your progress, keep up the great work!

Ursa_Adv · 10-28-2021, 05:31 PM

With the front mounts removed, I was able to rotate the motor into the proper position and boy did it feel good to get the swingarm bolt slotted in to place. Small victories.

There are a few areas of concern. The first is the front of the engine, there is a bolt that keeps the left/right side of the case together.

It rests ever so slightly against the frame. Removing the paint from the frame in that area was enough to allow it to slide freely without hanging up.

The next concern is the rear valve cover is right against the frame. Specifically the bolts are right against the frame. This is going to present an issue for valve adjustments.

I am going to check the length on the valve cover bolts, some creative spacing might give me a better clearance, but unsure if it will work. I don't like the idea having to take the swingarm off to slide the engine sideways to get clear of the frame each time I do the valves. My experience, however, on this build has shown me removing the swingarm takes a whole 5 minutes. So who knows

ExMxer · 10-28-2021, 06:24 PM

That looks great! As far as your frame issue with your valve adjust, could it be possible to have two new tubes contructed that attach to the upper spine? I don’t know the trouble you are willing to go to, but having two “shorter” rails connected to the spine would still maintain a solid structure, but giving you room to adjust your valves without removing the back half of your machine. Just a silly idea, this swap reminders me of a 2 stroke swap I helped a friend on years ago. Your work looks really good, hang in there!

Ursa_Adv · 10-28-2021, 08:53 PM

Quote:

Originally Posted by ExMxer

That looks great! As far as your frame issue with your valve adjust, could it be possible to have two new tubes contructed that attach to the upper spine? I don’t know the trouble you are willing to go to, but having two “shorter” rails connected to the spine would still maintain a solid structure, but giving you room to adjust your valves without removing the back half of your machine. Just a silly idea, this swap reminders me of a 2 stroke swap I helped a friend on years ago. Your work looks really good, hang in there!

Not a silly idea at all. As I was sitting there looking at it, I had the same thought. Like how could we "redo" these pipes back here. I, of course, rabbit holed into "Why don't I just make a new a frame?" That was my "too far" moment. lol.

As the goal for the swap was to use the stock frame, I am going to see what my fabricator says about options. I need to take the frame up there to have them plot out my engine mount situation, which will involve hauling the motor up there too, so we'll see.

I have a back-up option in the wings, if I really need it, but I'm trying to stick to the original goal of putting more power into my RXB. If I start swapping frames we get into that philosophical arguments of "is a thing still a thing if you take away all the parts", "cost vs. effort", etc.

ExMxer · 10-28-2021, 09:06 PM

Another stupid thought I had looking at your pics……. Looking at the bike from either side, look where the two tubes attach to the spine. Follow them down to where the meet, forming a Y. At that point, cut the larger of the 2 tubes just above where they meet straight across, following the tubes angle. Rotate that tube 90 degrees inwards toward the spine, trim the top edge of that tube and flange it to reattach to the spine. It looks as though that could gain you and inch minimum clearance, all while utilizing the OE frame and it’s materials. It’s merely, “modified”. Like I stated, just another silly thought, hope it makes sense…..

10-24-2021, 02:57 PM	#1
Plump Kibbles Join Date: Sep 2020 Location: Virginia Posts: 233	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! __________________ \|2020 X-Pro Titan DLX\| <-- FOR SALE!!
	0

10-25-2021, 05:19 PM	#5
Ursa_Adv Join Date: Jan 2021 Location: PNW Posts: 116	Turns out the Swingarm removal is way easier than I thought. Loosened the bolts up last night, I'll be pulling the swingarm in its entirety this evening. Then we're on to test fitting. *Note: I'm a turd and I labelled the 21mm nut on the swingarm a "21mm bolt".* __________________ NC250 Swapped '20 Orion RXB250L Build Thread
	1

10-27-2021, 05:02 PM	#8
Ursa_Adv Join Date: Jan 2021 Location: PNW Posts: 116	Test fit is complete. We ran into a few clearance issues. The front mounts for the motor are in the way. No matter which was you slice it, but we kinda knew that was a possibility going into it. So no real deal breaker. The other place we had a "hit" was the stock skid plate mount under the frame which was impacting the oil drain plug on the bottom of the engine. I used what was left in my angle grinder disk to remove the mount for the skid plate. I've got to pick up a new grinding disk and then I'll get started on the front mounts as well. At the end of the day, I need the rear mount (swingarm) to slot and align. The others, I can fab in later. __________________ NC250 Swapped '20 Orion RXB250L Build Thread
	3

10-28-2021, 05:31 PM	#12
Ursa_Adv Join Date: Jan 2021 Location: PNW Posts: 116	With the front mounts removed, I was able to rotate the motor into the proper position and boy did it feel good to get the swingarm bolt slotted in to place. Small victories. There are a few areas of concern. The first is the front of the engine, there is a bolt that keeps the left/right side of the case together. It rests ever so slightly against the frame. Removing the paint from the frame in that area was enough to allow it to slide freely without hanging up. The next concern is the rear valve cover is right against the frame. Specifically the bolts are right against the frame. This is going to present an issue for valve adjustments. I am going to check the length on the valve cover bolts, some creative spacing might give me a better clearance, but unsure if it will work. I don't like the idea having to take the swingarm off to slide the engine sideways to get clear of the frame each time I do the valves. My experience, however, on this build has shown me removing the swingarm takes a whole 5 minutes. So who knows __________________ NC250 Swapped '20 Orion RXB250L Build Thread
	0

10-25-2021, 07:11 PM	#6
China Rider 27 Join Date: Dec 2018 Location: PNW Posts: 982	With that full resolution zoom function you can get right in there and see it. That suspension looks beefy. Adjustable for rebound? Any issues with it?
	0

10-27-2021, 10:29 PM	#9
ExMxer Join Date: Jun 2021 Location: Earth, USA Posts: 196	Tilt that engine “up” about 3-6 mm….. from the front of course. Look at it from a down the road perspective. Raise up, before grinding down…..anything. Room is above, using the swing arm as a pivotal point, don’t use the cradle as a crutch. The more you can upright that cylinder, while keeping the cases somewhat level, the better off you’ll be. Sounds dumb as shit, but it does work. Hell, go 10 mm if needed….. that cylinder has a hell of an angle ahead of it. I really admire your work progress, swaps are a real test, keep it up!
	0

10-28-2021, 06:24 PM	#13
ExMxer Join Date: Jun 2021 Location: Earth, USA Posts: 196	That looks great! As far as your frame issue with your valve adjust, could it be possible to have two new tubes contructed that attach to the upper spine? I don’t know the trouble you are willing to go to, but having two “shorter” rails connected to the spine would still maintain a solid structure, but giving you room to adjust your valves without removing the back half of your machine. Just a silly idea, this swap reminders me of a 2 stroke swap I helped a friend on years ago. Your work looks really good, hang in there!
	0

10-28-2021, 09:06 PM	#15
ExMxer Join Date: Jun 2021 Location: Earth, USA Posts: 196	Another stupid thought I had looking at your pics……. Looking at the bike from either side, look where the two tubes attach to the spine. Follow them down to where the meet, forming a Y. At that point, cut the larger of the 2 tubes just above where they meet straight across, following the tubes angle. Rotate that tube 90 degrees inwards toward the spine, trim the top edge of that tube and flange it to reattach to the spine. It looks as though that could gain you and inch minimum clearance, all while utilizing the OE frame and it’s materials. It’s merely, “modified”. Like I stated, just another silly thought, hope it makes sense…..
	0