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

thereal87 wrote:

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

mnomis484 wrote:

I am in the process of rebuilding my 2012 YZ 250 and found a complete Linkage with new bearings off a 2009 yz250F on ebay. The...

I am in the process of rebuilding my 2012 YZ 250 and found a complete Linkage with new bearings off a 2009 yz250F on ebay.

The part numbers are different for the linkage as well as the connecting rod.

does anyone know if the linkage will bot onto my bike or does it only work if i install a 250f swingarm too?

mnomis484 wrote:

Thanks for the quick reply!

I understand now, i just wasnt sure if the 250f linkage would fit my 2 stroke swingarm

JM485 wrote:

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...

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. . .



. . . To zero just like that. . .



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-swing…

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.





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:





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.



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



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.

adam8781 wrote:

im running 09 yz250f rear end on my 06 swingarm linkage brake carrier rear hub. bolted right on, works great settles into corners a bit better...

im running 09 yz250f rear end on my 06

swingarm
linkage
brake carrier
rear hub.
bolted right on,

works great settles into corners a bit better, other than that i dont notice anything really .

AHarmon237 wrote:

Bringing this thread back from the dead... Did you use the 2009 yz250f linkage arm and linkage knuckle? Did you use the yz250 2 stroke shock...

Bringing this thread back from the dead... Did you use the 2009 yz250f linkage arm and linkage knuckle? Did you use the yz250 2 stroke shock as well?

cdoggy81 wrote:

Is there a washer under the nut?

15tc150 wrote:

Mmmmmmmay be read a little closer..... [img]https://p.vitalmx.com/photos/forums/2020/10/04/452637/s1200_B114760C_398B_4B3E_964D_A41001E0C1D8.jpg[/img]

Mmmmmmmay be read a little closer.....

cdoggy81 wrote:

That’s good you figured it out. Can you post some pics of the gaps / alignment issues / etc?
Thanks 👍🏻