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2001 YZ426 Clutch Assembly in a 2003 YZ450F?


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Firstly, hola! First post, new rider, go easy please. 
Second, I have reviewed the service manuals, online diagrams from various sources as well as online parts catalogs for each of these bikes. 
 

I recently picked up a 2003 yz450f of unknown hours. It’s in fair shape but does not run or ride well. I’ll likely make a separate topic post regarding the running issues. The concern I’m trying to address here is the clutch. It shows ever issue possible. Dragging, no achievable free-play, neutral is impossible to find and it simply does not shift well. So, obviously I tore it apart. Now, this is my first full size bike. I’ve rebuilt my Chinese four stroke four wheeler and my 2018 Apollo 125cc. I’m also a certified master technician with a bit of time under my belt in automotive work. 

After I took the clutch apart I noticed several things that were odd to me. Granted, I have no background in bikes. The fiber discs, while obviously worn to an extend all measured at or above the factory spec of ~3mm. The steels, while slightly discolored, showed no warpage on a flat steel surface using a .1mm feeler. The major difference came when I looked in the bottom of the basket to find that it starts with a steel plate. Now, in my diagram this is not what it shows. And beneath this steel plate there are two bevel springs. Also not in my manual. After some research I find that my top pressure plate is for a yz426 judging by the casting mark. After reviewing the diagram for a yz426 clutch I find that it contains these two bevel springs where the yz450 does not.

Long story short: Is it a common mod to fit a 2001 yz426 clutch kit to a 2003 yz450f or did the previous owner make a mistake? 

Thanks!
 

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I did just find this for a clutch mod that calls for some previous gen parts. However if this person described it correctly, this is not what I have going on from what I can tell. It more appears that an entire 426 assembly is install in my 450. 

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Posted (edited)

Seriously doubt that my friend. It looks to me that someone did not know what they were doing. As you have realised, there should never be steel against alloy in the clutch. There should always be friction disc between two metal surfaces. The YZF should have alternating friction discs and clutch plates all the way through. It does not have anti-judder springs in it (the bevel springs you have pictured). From the parts, it does certainly appear to be a 426 clutch, as that does have the anti-judder springs, and the first friction disc is much thinner radially to go with them. Still not metal on metal. For the life of me, I can't think why one would do that. If the friction discs are still within spec, and the plates are not warped, I would take it back to stock if I were you.

Edited by ThumpaGreg
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I believe that, along w/ the judder spring, the first friction plate should be thinner to accommodate the judder spring. The judder spring is supposed to spin/rest on a hardened washer...

Basically the '01 clutch replaced the first plate with the washer-spring-thinner friction*. 

At any rate my guess is your engaging parts (rod & etc.) are not the proper length for the total thickness of your clutch stack..

If that is the case my choice would be stock '00 426 configuration, since I wouldn't want to have to replace the basket and everything, and in this case it would appear you only lack one part? Or just remove the two judder springs (which should actually be one spring and one hardened inner "Plate Seat")? I'm not sure as I can't find an '00 fiche at the moment.

Hope this helps

 

* this was due to grabbiness brought on by the innermost disc sticking to the boss. I owned both an '00 and '01 and nearly everybody back then (that was experiencing this problem) fixed the former with a Hinson basket. It was thought the issue was poor oiling and the Hinson basket fixed it. That said my '01 clutch was fine and I left it stock.

Edited by Hick
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