'20 RXB250L - NC250 Motor Swap [Build Thread] - Page 3

Ursa_Adv · 10-28-2021, 09:53 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, 10:06 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…..

Ursa_Adv · 10-28-2021, 10:32 PM

Quote:

Originally Posted by ExMxer

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…..

I think I'm following. Something like this (simplified I know), right?

China Rider 27 · 10-28-2021, 11:40 PM

I think you are right to explore all options by taking off those valve covers and see how they are put together. I was thinking putting a stud in but doesn't look like there is enough room to
work. Grinding down the cover where the bolts are located? Custom valve cover? Just some Thoughts. Looks like it will work just question of how.

ExMxer · 10-28-2021, 11:56 PM

Quote:

Originally Posted by Ursa_Adv

I think I'm following. Something like this (simplified I know), right?

Bingo!! You think that might work?? Granted, I'm just going off pics.... Just thought rather than spend a lot of time, and of course money, on fab work, utilize what is already there. Just tweak it a tad, all while still remaining solid, and safe. Thoughts? Besides, I think the tubes would be of length needed (you probably trim off an inch or so), because their new attach points would be lower than before, due to the drop of the spinal tube.

david3921 · 10-29-2021, 11:35 PM

You may also think about using the engine as a stressed member. This would allow you to rotate the engine down a bit more to allow clearance for the intake valves. It may be just the way the photo is taken (first photo, post #29), but it looks like the engine it rotated clockwise too much so that it clears the frame.

Ursa_Adv · 10-30-2021, 02:16 PM

Quote:

Originally Posted by david3921

You may also think about using the engine as a stressed member. This would allow you to rotate the engine down a bit more to allow clearance for the intake valves. It may be just the way the photo is taken (first photo, post #29), but it looks like the engine it rotated clockwise too much so that it clears the frame.

Currently, it does have to sit more clockwise than I would like due to the frame. Which further causes the valve cover issue.

If I am following you, by using the engine as a stress member, I would be able to remove a bit of the frame and use the overall strength of the engine as part of the "triangle".

A bit like this?

david3921 · 10-30-2021, 03:09 PM

Quote:

Originally Posted by Ursa_Adv

Currently, it does have to sit more clockwise than I would like due to the frame. Which further causes the valve cover issue.

If I am following you, by using the engine as a stress member, I would be able to remove a bit of the frame and use the overall strength of the engine as part of the "triangle".

A bit like this?

Yes. You'd still be able to add a skid/bash plate to protect the underside of the engine. Also, by doing so, it looks like you would have an easier time attaching the top of the engine to the cross brace.

XLsior · 10-30-2021, 04:37 PM

Looks to me like this frame was not designed with the counter balanced case protrusion in mind.

I personally wouldn't move or alter any of the upper frame structure.

The way it appears clocked the sprocket to swingarm and rear hub line seems like it would possibly lead to chain wear interference.

I think the main focal point or frame alteration is around the counter balance case protrusion.

There's a couple of options. You could shave out frame material around the counterbalance, I don't think there is enough meat to the frame for this.
You could make a cut where the bottom red arrow is in the photo and put a pie cut kink/dogleg moving the frame towards the front wheel and filling in the lower frame section extension.
Or you could cut out the whole section and fabricate an engine mount/frame tie in bracket. A bit like my Honda Xl185.

XLsior · 10-30-2021, 04:53 PM

You might be able to incorporate a lower engine mount with the infill frame extension section.

The upper front mount might also be able to be incorporated into the frame adjustment pie cut portion where the frame will bend out towards the front wheel..

However not sure if these fixed mounts will make taking the engine out or putting it back in impossible due to space constraints.

Just throwing ideas.

Britt · 10-30-2021, 05:19 PM

Do not use the engine as a stress member. The cast casing material was NOT designed to deal with that stress and would most likely crack.

Ursa_Adv · 10-30-2021, 06:34 PM

Quote:

Originally Posted by Britt

Do not use the engine as a stress member. The cast casing material was NOT designed to deal with that stress and would most likely crack.

I do want to be clear at this point, I'm not intending to do any modifications of the frame. I do, however, enjoy the discussions we have going on frame modifications and am willing to entertain any ideas the community has.

I agree with you on not using the engine as a stress member, but it was an interesting thought.

My backup plan is still in place if I can't get the engine where I want it without a full redesign of the frame.

China Rider 27 · 10-30-2021, 07:27 PM

I agree no way would I modify the upper frame. Any frame mods would have to be on the engine cradle. Xlsior idea has the most merit but I would cut the bottom rails way back under the engine or even some more. Decide where on the front down piece to tie in and just slide that section forward an inch or so. You could maybe take some smaller square tubing and sleeve the two bottom pieces the top would have to be rebuilt. As said though we don't know the effect on pushing out the front an inch or two. Looks like you only need about an inch. If you imagine taking the cradle as is and cutting it at three points then just extending it forward an inch. BUT as you said this is just a mental exercise and I am no way recommending you cut the frame.

david3921 · 10-31-2021, 02:58 AM

Quote:

Originally Posted by Ursa_Adv

I do want to be clear at this point, I'm not intending to do any modifications of the frame. I do, however, enjoy the discussions we have going on frame modifications and am willing to entertain any ideas the community has.

I agree with you on not using the engine as a stress member, but it was an interesting thought.

My backup plan is still in place if I can't get the engine where I want it without a full redesign of the frame.

As we just throwing ideas around, I guess I could have been a little more clear. I was thinking more along the lines as what Suzuki does with some of their thumper models. The TU250 uses the engine as a stressed member. I was thinking something similar but welding on a skid plate for added strength. This would allow clearance for the counter balancer.

On another note, the DR250 also pretty much does the same thing (as do the SSR/Qlink/Qinqi versions) except two small diameter tubes are bolted on the bottom to add the plate and provide a bit more rigidity.

Ursa_Adv · 10-31-2021, 03:03 PM

All really good ideas.

I'll be talking with the welder/fabricator tomorrow morning. I think the most practical choice so far is to just extend the engine cradle in the front 1.5 inches to make more room for the counter balancer so the engine can rotate fully downwards.

So for right now the next update is going to be around getting the frame squared away.
Probably happen in a day or two.

To everyone watching this thread. Thank you for keeping up with things and we'll get back to the fun as soon as we can get the engine sitting pretty.

If anyone wants pictures or would like to see specific parts of the Orion frame, let me know.

10-29-2021, 11:35 PM	#36
david3921 Join Date: Feb 2009 Location: Michigan Posts: 1,043	You may also think about using the engine as a stressed member. This would allow you to rotate the engine down a bit more to allow clearance for the intake valves. It may be just the way the photo is taken (first photo, post #29), but it looks like the engine it rotated clockwise too much so that it clears the frame. __________________ 2012 Kawasaki Versys 1984 Honda Magna V65 2016 Rhino 250 2016 Tao Tao 125D
	0

10-30-2021, 05:19 PM	#41
Britt Join Date: Jun 2021 Posts: 61	Do not use the engine as a stress member. The cast casing material was NOT designed to deal with that stress and would most likely crack. __________________ 2022 KLR650 2021 Hawk DLX 2021 Lifan Xpect 2021 Hawk 150 (RPS Viper)
	0

10-31-2021, 03:03 PM	#45
Ursa_Adv Join Date: Jan 2021 Location: PNW Posts: 118	All really good ideas. I'll be talking with the welder/fabricator tomorrow morning. I think the most practical choice so far is to just extend the engine cradle in the front 1.5 inches to make more room for the counter balancer so the engine can rotate fully downwards. So for right now the next update is going to be around getting the frame squared away. Probably happen in a day or two. To everyone watching this thread. Thank you for keeping up with things and we'll get back to the fun as soon as we can get the engine sitting pretty. If anyone wants pictures or would like to see specific parts of the Orion frame, let me know. __________________ NC250 Swapped '20 Orion RXB250L Build Thread
	0

10-28-2021, 10:06 PM	#32
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

10-28-2021, 11:40 PM	#34
China Rider 27 Join Date: Dec 2018 Location: PNW Posts: 984	I think you are right to explore all options by taking off those valve covers and see how they are put together. I was thinking putting a stud in but doesn't look like there is enough room to work. Grinding down the cover where the bolts are located? Custom valve cover? Just some Thoughts. Looks like it will work just question of how.
	0

10-30-2021, 04:37 PM	#39
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,455	Looks to me like this frame was not designed with the counter balanced case protrusion in mind. I personally wouldn't move or alter any of the upper frame structure. The way it appears clocked the sprocket to swingarm and rear hub line seems like it would possibly lead to chain wear interference. I think the main focal point or frame alteration is around the counter balance case protrusion. There's a couple of options. You could shave out frame material around the counterbalance, I don't think there is enough meat to the frame for this. You could make a cut where the bottom red arrow is in the photo and put a pie cut kink/dogleg moving the frame towards the front wheel and filling in the lower frame section extension. Or you could cut out the whole section and fabricate an engine mount/frame tie in bracket. A bit like my Honda Xl185.
	1

10-30-2021, 07:27 PM	#43
China Rider 27 Join Date: Dec 2018 Location: PNW Posts: 984	I agree no way would I modify the upper frame. Any frame mods would have to be on the engine cradle. Xlsior idea has the most merit but I would cut the bottom rails way back under the engine or even some more. Decide where on the front down piece to tie in and just slide that section forward an inch or so. You could maybe take some smaller square tubing and sleeve the two bottom pieces the top would have to be rebuilt. As said though we don't know the effect on pushing out the front an inch or two. Looks like you only need about an inch. If you imagine taking the cradle as is and cutting it at three points then just extending it forward an inch. BUT as you said this is just a mental exercise and I am no way recommending you cut the frame.
	0