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YZ 125 right case cover and forks question

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Hi guys

My bike (YZ 125 '02) needs a new right case cover, the one with the powervalve governor and water impeller in it. One has popped up for sale recently and although it is visually identical to the old one, the owner claims it came from an older bike (something like 1998). Checking it on parts fiche does produce slight variations in part numbers. The 1998 = 4JY-15431-00-00, the 2000 = 4JY-15431-12-00 and the 2002 = 4JY-15431-13-00. Does anyone know the year by year changes made to the cover? I'm quite confident it would just bolt on and work, but I'd like to be sure that the older part is not in some way drastically inferior to my current one. Attached pics.

 

And now about the forks. Same bike (YZ 125 '02). I bought a set of used forks in a reasonable visual condition which I'm 99% percent sure are the old open-cartridge 46mm forks. The only different thing on them is the fork top cap. Could anyone tell me what the difference is between those three fork caps on the pic (attached)?

Thanks very much

110060001001.jpg

cover_1.jpg

cover_2.jpg

Edited by Narciss

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Not 100% on case cover. but I believe the 98-04 are the same with minor variations but not mounting problem.

DO NOT TAKE MY WORD FOR ANY OF IT.

Fork caps are

Top:I have seen those on 2003

Right: 2004 48mm although I bought an 02 that had same caps and they were 46mm

Bottom: I have seen them on 98-2002 and poss-earlier.

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Did you figure out where the crank case cover fits. I'm look at putting a 2003 crank case cover on a 1997. The part number difference is 1997 = 4JY-15431-00 and 2003 = 4JY-15431-14

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No, ended up not buying the cover (yet?) so can't really help you. Probably some minor updates in casting, so as to make it stronger and lighter. Mounting should not be a problem IMO, as the cases didn't really change until 2004..

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On 30/08/2017 at 9:07 PM, EEE299 said:

They are both XXX-15431-XX-XX so they are interchangeable.

Not sure about just the numbers being a guaranteed match. Check the 2002 YZ 125 and 2016 YZ250F fuel tank numbers. XXX-24110-XX-XX, but they surely don't match.

 

Not really the same with the mentioned case cover.. though I'd still take my old one before buying a used piece and compare side by side.

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5 minutes ago, Narciss said:

Not sure about just the numbers being a guaranteed match. Check the 2002 YZ 125 and 2016 YZ250F fuel tank numbers. XXX-24110-XX-XX, but they surely don't match.

 

Not really the same with the mentioned case cover.. though I'd still take my old one before buying a used piece and compare side by side.

Interesting. I follow the old thread on part numbers and haven't found any that didn't work yet.

If you're right and those tanks wont bolt up then maybe I'm wrong. Like I said I've had no problems, but I've also never tried parts from such different models as the 02 yz125/16 yz250f.

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The frame is all different, no way that would interchange. I mean, it probably a safe bet doing it as long as you know what year the major changes were made. So for example this cover is visually the same from what, '96-'04? That means it's a proper chance it would bolt straight up. Still, I'd double check before buying. :) 

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Yes, it's always good to check.

Part #s

EDIT: After re-reading I'm assuming the first three digits must match as well, my bad:facepalm:

Edited by EEE299

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I would check part numbers on any shafts, or bearings that are pressed in to that case cover. Sometimes the casting is the same, but the interior machining has changed to accomodate different sized transmission shafts or bearings.

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you can't go by strickly the parts numbers for Yamaha parts because Yamaha changes the numbering scheme too often. I believe that most engine parts interchange from 96 to 2004 with the exception of cylinders (different pipe mount in 99) and transmission 6 spd vs 5 spd.

 

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On 02/09/2017 at 1:32 AM, 351mustanger said:

I would check part numbers on any shafts, or bearings that are pressed in to that case cover. Sometimes the casting is the same, but the interior machining has changed to accomodate different sized transmission shafts or bearings.

Good thinking. Great tip.

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