YZ250 Swingarm Update the Right Way (Not the MXA way)

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12/5/2017 7:55 PM
Edited Date/Time: 12/5/2017 8:03 PM

Well, after finally getting this swap figured out once and for all, I figured I would share how I went about putting the modern style four stroke swingarm on my 15 YZ250. This all came about after an unfortunate failure at the Reno endurocross this year. As second practice started, I proceeded to launch the finish line jump and get set to begin my fast lap. Upon landing, however, my chain guide snapped off the swingarm and wrapped its was around my sprocket, breaking my hub and ending my day on the big bikes. I was obviously super mad at the time, but after some time to reflect I realized I should really count my blessings that it did not snap off on the lip, we would probably be having a very different thread right now. . . I basically went from hero. . .

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. . . To zero just like that. . .

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So, I basically had a choice to make, replace it with another old design swingarm, or update the bike with the new style swingarm. I chose the later, and opened up a much bigger can of worms then I expected. After some research, I came across this article from MXA, and used it as my guide for the project:

https://motocrossactionmag.com/ask-the-mxperts-can-i-put-a-yz450f-swingarm-on-my-yz250-two-stroke/

Now, according to them you can simply bolt the new swingarm and linkage onto the two stroke, as long as you have the wheel and brake hanger. Following this guide, I bought a swingarm and linkage off of a fellow Vital member's blown 2014 YZ250F, as well as a hub, spokes, and rim (18" this time around). Upon receiving the swingarm, I realized that I would need my swingarm spacers, which was no big deal since they slipped right into the 450 swingarm. The issue came when I bolted the linkage up. Yes, the linkage will bolt up, but you'd have to be a complete moran to think this is acceptable. The linkage was completely kicked over to the side, and any riding would have resulted in the pull arm digging into my frame and an unevenly worn shock. Naturally, I assumed the swingarm was bent, so I proceeded to contact the seller and make a complete ass out of myself convincing him to take the parts back, which he agreed to. I then went onto Ebay, and bought a used 2014 YZ450F swingarm.



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Upon receiving the new swingarm, I bolted it onto the bike. To my surprise, I found exactly the same thing, linkage was completely off-center and would rub on my frame. The realization began to set in that the linkage mount on the new 450 swingarms is actually offset to the side slightly. I don't know who is writing articles for MXA, but if they were really "speaking from experience" with that article, there's no way in hell they would have been able to call this fit acceptable. I ended up calling the seller of the first swingarm, apologizing, and eating about $150 in shipping costs because I was clearly at fault. Thanks MXA, glad you did your due diligence before leading people astray with your article. . .

Now, I had to go about fixing it. After some careful measurements, I found that the linkage mount is offset .175" on the new swingarms. This meant I had to mill that amount from one side of the swingarm, and machine a spacer to take up the space on the other side. Here is what I came up with:

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Here is how everything fit after the modifications. Everything lined up perfectly, and the pull arm was centered nicely between the frame mounts. Keep in mind, you will need the four stroke linkage as well in order to keep the rising rate the same (according the MXA so who really knows. . .), and I used a set off a WR250 since it was the same.

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Looks pretty darn good on the bike to IMO, much better than the old design!

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Now, most importantly, how does it ride? In a word. . .Awesome! I don't think that the linkage rising rate is quite the same as the old two stroke linkage, but to me the new setup is an improvement. I've always struggles with front end traction on this bike, and with this setup the back end had a little more holdup to keep things planted on the front. I can now run more sag and still have a balanced setup, which is great! I also feel that the back kicks a little less than previously, but nothing earth shattering. For someone with a perfectly good swingarm and linkage setup on their YZ, I don't think this swap is worth it financially for the performance gained, but if you want a project or have had a similar failure I would definitely recommend it. I have been told that the 09+ swingarms before they went to the reverse motor design will bolt right up with no offset on the linkage, but I have not confirmed this so proceed with caution. Why Yamaha doesn't do this from the factory I have no idea, it seems like a no brainer to me since the performance gain is noticeable.

Hopefully this little write up will guide others through the project and dispel a few rumors about this swap. If anyone has any questions please let me know, I only have two rides on it so far so I will be learning more about the bike over time. Watch out for misinformation out there, I figured a reputable website like MXA would have trustworthy information but apparently not. This whole fiasco cost me a decent amount is shipping, but more importantly caused me to miss the final round of the endurocross series in Ontario, which I had been planning n racing.

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Make Hillclimb Great Again

Ratbeach Racing

Instagram / YouTube: @485Josh

3dpmoto.com



12/5/2017 8:52 PM

Thanks for the write up, I have been looking into this.
I also want to change brake pedals to the sleeker 4 stroke one. No performance just looks cool.

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12/5/2017 9:36 PM

The linkage ratio is indeed different, though not terribly much. There's slightly less stiffness early in the shock stroke with a tiny bit more bottoming resistance. Most people probably won't notice any difference:

Photo

This is for a 2009 450 swingarm and 2009 250F complete linkage, which all bolts right up without issue (no offset linkage issues like you had on the newer swingarm).

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Motocross Components Engineered for Performance

12/6/2017 1:21 AM

Great info and awesome write up.
Nice job on the machine work too!

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@russ_69

12/6/2017 1:28 AM

Great article, thanks for all the detailed info and photos. Very helpful!

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2020 YZ450F
2006 YZ125
2013 YZ 250F special edition
2017 YZ 250
2015 YZ 250f soecial edition
2019 KTM 85 big wheel

12/6/2017 5:35 AM

That is weird, I installed a 2014 YZ250F swingarm and linkage on my 2012 YZ125 and it lined up perfectly.

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12/7/2017 4:20 PM

Luxon MX wrote:

The linkage ratio is indeed different, though not terribly much. There's slightly less stiffness early in the shock stroke with a tiny bit more bottoming resistance. Most people probably won't notice any difference:

Photo

This is for a 2009 450 swingarm and 2009 250F complete linkage, which all bolts right up without issue (no offset linkage issues like you had on the newer swingarm).

Good stuff, thanks for the info! Interesting that it's so close, I wonder if I was feeling a little difference in the flex and mistaking it for a rising rate difference.

BTW, thanks again for the help you gave me on my resume, I've been working at a job I got shortly after and I have to imagine that played a big role. I've also been following along as you develope the new triple clamps, it's been a really cool process and made me realize just how little I really know.laughing I'm learning a lot in industry though, my Solidworks skills have definitely improved quite a bit, and I've learned about a few different manufacturing processes I wasn't aware of before.

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Make Hillclimb Great Again

Ratbeach Racing

Instagram / YouTube: @485Josh

3dpmoto.com



12/7/2017 4:21 PM

Sheriff245 wrote:

That is weird, I installed a 2014 YZ250F swingarm and linkage on my 2012 YZ125 and it lined up perfectly.

Something doesn't add up here, because mine was way off, as shown above. Is it possible there was a mid year change in the line, or that the 250 did not share the 450 swingarm at the time?

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Make Hillclimb Great Again

Ratbeach Racing

Instagram / YouTube: @485Josh

3dpmoto.com



12/7/2017 6:03 PM

JM485 wrote:

Good stuff, thanks for the info! Interesting that it's so close, I wonder if I was feeling a little difference in the flex and mistaking it for a rising rate difference.

BTW, thanks again for the help you gave me on my resume, I've been working at a job I got shortly after and I have to imagine that played a big role. I've also been following along as you develope the new triple clamps, it's been a really cool process and made me realize just how little I really know.laughing I'm learning a lot in industry though, my Solidworks skills have definitely improved quite a bit, and I've learned about a few different manufacturing processes I wasn't aware of before.

No problem, I worked that up a few years back when I did the swap. And glad to hear things are going well for you!

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Motocross Components Engineered for Performance

12/7/2017 7:14 PM

JM485 wrote:

Something doesn't add up here, because mine was way off, as shown above. Is it possible there was a mid year change in the line, or that the 250 did not share the 450 swingarm at the time?

I remember mix and matching a few spacers and bolts, but nothing more. Maybe there was a mid year change.

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12/8/2017 4:13 PM

So what years will fit without machining? There is a 2010 450f part out I could grab.
The 250 and 450 are different the 450 is longer, so maybe because if this they also decided to offset the linkage.

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12/8/2017 10:09 PM

Zesiger 112 wrote:

So what years will fit without machining? There is a 2010 450f part out I could grab.
The 250 and 450 are different the 450 is longer, so maybe because if this they also decided to offset the linkage.

If I had to guess they changed it after the reverse motor design, which started in 2010. It's kind of a gamble, but if you have any access to equipment it can be made to work as you can see. The 2014 arm I got is a generation newer then that 2010 though, so it's possible that it will line up, but I would maybe check part number against on 09 to see if they are the same. To be completely honest with you though, it looks a lot better and does ride a little differently, but if you have a perfectly good swingarm on your bike I wouldn't go through the hassle, it just isn't worth it IMO.

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Make Hillclimb Great Again

Ratbeach Racing

Instagram / YouTube: @485Josh

3dpmoto.com



12/9/2017 6:18 AM

i took 09 250f stuff and bolted it rite on to my 12 yz guy i sold it to is still running it i did two 16 yz 125s with ebay parts from not sure what year bikes and they were fine also

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12/9/2017 6:50 AM

Very, very interesting. I’m sorry you had to spend money for my learning, but I enjoy the technical stuff. Congrats on the unique setup.

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12/9/2017 10:11 AM

Anybody know if there are differences between 250f and 450f swingarms?? Maybe in lengths etc. or anything else?

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12/9/2017 1:40 PM

b_kowalsk wrote:

Anybody know if there are differences between 250f and 450f swingarms?? Maybe in lengths etc. or anything else?

I've always seen the 450 is longer than the 250 and the 250 is about the same length as the yz250. So the 450 puts more weight on the front.

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12/9/2017 3:06 PM
Edited Date/Time: 12/9/2017 5:08 PM

Alright here is what I have found.
2009 is known as the go to bolt up.
2010 is what I am looking at
And the 2014 mentioned here some work some don't.

2009 250 17d 22110 00 00
2009 450 34p 22110 00 00 (suppose to be longer)

2010 250 17d 22110 00 00 same as 2009
2010 450 33d 22110 00 00 different from 2009

2014 250 1sl 22110 01 00 different
2014 450 1sl 22110 01 00 different
-noted below that they suppersede 1sl 22110 00 00
So there may have been some kind of mid year change in 2014 because they changed to 01 in that column. 2013 had the 00 number but 14 was also the first year for the next generation.

In 2010 they changed the 450 to reverse engine but not the 250. I read in a review for that the shock was center mounted because there was no need for an airboot. So I would just stay away from any later than 2009 in the 450. However the 250 should work up until 2014 but it isn't going to be longer, but it will still be lighter.

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12/9/2017 4:00 PM

^^ Awesome info ^^
Was looking into the swap a little bit myself just for the weight loss and cool factor. For those wondering the YZ125 and the YZ250 show the same part number and use the same swing arms so judging by that, this swap should be the same with both 125's and 250's.

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12/9/2017 6:41 PM

Luxon MX wrote:

The linkage ratio is indeed different, though not terribly much. There's slightly less stiffness early in the shock stroke with a tiny bit more bottoming resistance. Most people probably won't notice any difference:

Photo

This is for a 2009 450 swingarm and 2009 250F complete linkage, which all bolts right up without issue (no offset linkage issues like you had on the newer swingarm).

Billy, can you draw a straight line on that graph that shows shock position when running 105mm sag?

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12/10/2017 3:18 PM

Bruce372 wrote:

Billy, can you draw a straight line on that graph that shows shock position when running 105mm sag?

Hey Bruce, 105mm wheel travel is about 26% shock compression on the plot (orange line):

Photo

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Billy Wight
Luxon MX
@LuxonMX
https://luxonmx.com
Motocross Components Engineered for Performance

12/12/2017 12:13 PM

That sucks to have to go through all of that. I bolted up a 09 250f swingarm on my 250 and didnt have an issue.

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YZ250X
YZ125

IG - @mattman122

12/14/2017 10:01 AM

I had the chance to try a 2012 yzf450 swingarm+linkage on my 2007 yz250 and it doesn't fit.Had the same problem as JM485.

the axle through the frame/swingarm is also 1mm smaller on the 4 stroke so you have to switch the bushings from the swingarm bearings.

Also the swingarm was about 5mm shorter than my 2 stroke swingarm

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1/5/2018 12:30 PM

Hmmm..... That sux it didn't work for you guys.
I just did the conversion myself on my 2011 yz250. Used a 2010 yzf450 swingarm, linkage & wheel & it bolted right up. I thought the 2009-2013 yzf450 & 2010-2013 yzf250 bolt right up (I forget why the 1 year diff or I may be just confusing it with the 22mm triple clamp conversion I also did).
I'll be posting a thread here soon :]

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5/21/2018 6:02 PM
Edited Date/Time: 5/21/2018 6:03 PM

Anyone know if you can use a late model (2016) 450 pivot shaft in the yz frame?

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5/22/2018 8:37 AM

No, the axle through the frame/swingarm is 1mm smaller on the 4 stroke so you have to switch the bushings from the swingarm bearings and use the pivot shaft from a 2 stroke

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5/22/2018 10:07 AM

Matthias_26 wrote:

I had the chance to try a 2012 yzf450 swingarm+linkage on my 2007 yz250 and it doesn't fit.Had the same problem as JM485.

the axle through the frame/swingarm is also 1mm smaller on the 4 stroke so you have to switch the bushings from the swingarm bearings.

Also the swingarm was about 5mm shorter than my 2 stroke swingarm

Photo


Are you using the "F" rocker or the stock one from the YZ?

Also, you don't have to swap the axle, hub, bearings, axle blocks or brake carrier with the swingarm swap.

YAMAHA uses the same wheel set up on the "FX" 250 / 450 as they do on the YZ250X, which is the same as the standard YZ, but with an 18" rim and the "FX" and "F" use the same swingarm.

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5/22/2018 10:35 AM

I used a complete linkage and swingarm from a 2012 yz450f

So the FX 250/450 has a '4stroke' swingarm(without the plastic plugs) but uses a 22mm axle? How do they fill up the 3mm play in the swingarm ends?

The problem as shown in my picture stays I guess, the shock on a 4 stroke is more located to 1 side?

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5/22/2018 4:58 PM

Yamaha fx and wrf run their own swingarm, it looks the same as the yzf swingarm but runs the small axel like the yz 2 strokes

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5/22/2018 5:01 PM

Luxon MX wrote:

The linkage ratio is indeed different, though not terribly much. There's slightly less stiffness early in the shock stroke with a tiny bit more bottoming resistance. Most people probably won't notice any difference:

Photo

This is for a 2009 450 swingarm and 2009 250F complete linkage, which all bolts right up without issue (no offset linkage issues like you had on the newer swingarm).

Hey billy, just to 100% confirm it before I lay out cash on these parts, I should track down 09 yzf swingarm, linkages (pull rod and knuckle) rear axel, caliper bracket and hub? Thanks in advance

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5/22/2018 5:07 PM
Edited Date/Time: 5/22/2018 5:11 PM

Luxon MX wrote:

The linkage ratio is indeed different, though not terribly much. There's slightly less stiffness early in the shock stroke with a tiny bit more bottoming resistance. Most people probably won't notice any difference:

Photo

This is for a 2009 450 swingarm and 2009 250F complete linkage, which all bolts right up without issue (no offset linkage issues like you had on the newer swingarm).

thereal87 wrote:

Hey billy, just to 100% confirm it before I lay out cash on these parts, I should track down 09 yzf swingarm, linkages (pull rod and knuckle) rear axel, caliper bracket and hub? Thanks in advance

And chain guide and axle blocks, know the 450 is longer than the 250. On the 125 I'd probably go with the shorter 250 to maintain tight handling. There is a guy on here selling a 2009 250f swingarm for $150 with chain guide and axle. He also has a complete rear wheel. I bought the brake caliper and bracket from him. The post is something like yz250f parts for sale.

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