Slipping third gear

Hi all

I have split the case on my wr426 2001 and found the selector fork is worn where it should not be and not all that  much on the fingers themselves.

I will upload more pics tomorrow to display.  Is it possible the fork has warped? It seems odd only half of the plating of the finger has been taken off and its into the guts of the fork?

The dogs are rounded  on 3 and 5 primary as well and they are starting to pit (see photo)

So I need to replace 3 and 5 primary gears as well

What number fork is it?


Do I need to replace the macthing driven gears as well?  I plan on rding the bike 20 -30 hours before selling


cheers rileyp

Edited by rileyp

Make, model, and year please?


I'll guess it's a 426.  If third is the one "slipping" or "skipping" in/out of gear, the two gears that need to be replaced are the 3rd and 5th gears on the output shaft.  3 and 5 on the main shaft work to engage 5th, not third.  The meshing gears in either case need only be replaced if there is some reason for it apart from the lug damage to their mate. 


The fork is bent.  The wear in the center is due to the fork being forced to flex far enough to allow the 5th slider to move far enough away from third to separate the two. 

Thanks for the fast reply. Ive edited my post to include make and model :)

I havent riiden the bike to see third slip. I bought it and the seller informed me of the situation and i thought ok $500 should cover selector forks and any gears that needs replacing and some gaskets along with a heap of my time.

So your saying the gears photographed are not the cause of the slipping as the selector on this shaft is used to engage fifth and not third. The dogs on these two gears are worn badly.

I will have a better look at the output shaft this arvo and post up some pics.

Edited by rileyp

OK, I'm guessing again and saying that that picture shows the main, or input shaft, and that the right, or clutch end of the shaft is at the right of the picture.  In that case then, yes, it's true that the "slider" (the gear that the shift fork slides back and forth) in that picture is the third gear pinion, and it is used to lock either the fourth gear pinion or the fifth gear pinion (which are otherwise free to spin on the shaft) to the shaft, thereby making that gear the driving pair, or, "engaged".   They have nothing to do with engaging third gear.  That job is handled by the 5th wheel gear (gears on the output shaft are "wheels", gears on the input are "pinions") on the out put shaft.


The two gears shown are damaged, certainly enough, but the problem that causes the gears to force themselves out of engagement is wear at the surfaces of the locking lugs on the gear sides (yellow arrows).  Those in the picture look pretty good, really.  The damage to third gear on the tooth (red arrow) is probably the result of all the slamming back and forth that goes on when this happens.  I'd be surprised if the meshing 3rd wheel doesn't show something on the facing tooth surfaces.  The damage to the adjacent 4th pinion is likely from a frag off of 3rd.


Thanks again for your help grayracer513


I noticed you are a Mod so could you please move this post into the WR 426 forum . I had great fun trying to find it ;) I posted in here by mistake :(



All the dogs on the the output shaft all look very square and almost new looking and its two selector forks look ok as well.


The dogs on the fifth side of No 3 primary gear are absolutely trashed which is consistant with the wear on the centre of shift fork 2 and the bending of the fork to do so.


The seller told me it was jumping out of third.

I never rode it. but Im putting my money on it was jumping out of fifth. He said he rode it on the road more than anything which to me says... riding it hard in fifth for extended periods of time... not third as he liives on the outskirts of town.

Heres some pics of the trashed dogs on 3 primary on its fifth side

The dog gear mating face looks like a ski slope when looking side on!


Uploaded with



Uploaded with


Fourth primary gear has five or six  pits in it as pictured below (second gear from LSH)  If i keep clean oil in it and I'm not throwing round chunks of selector fork steel would it be fair to say I would get away without replacing it?  I know best practice would be to replace.

Third primarys faces  are completey ruined s in the shot as well (Far RHS) but I will definately have to replace it!



Uploaded with




Any advice greatly appreciated!

cheers Rileyp

Edited by rileyp

I wouldn't reuse the 4th pinion looking like that, no.  Not for no more than it will cost to add that to the stack. 


But high mileage isn't what does it.  Here's one from my '06 YZ450, with over 300 hours of mostly desert and GP, with lots of time spent in 5th.  Shifting is what does it, or doesn't, depending on how it's done.  That, and and oil that's really good enough for use as a gear oil.





I rebuilt my transmission on my 2002 wr426 and fyi you should really change out all the gears that you can see noticeable wear. If you are in doubt in where to get parts and don't mind waiting a couple days, go online @ and get your parts there. They're seriously the cheapest place to buy factory parts. I have to replace like 80% of my transmission.


I have in my favourites :) partshark is also very good

Though being in Aus I'm going to give a try . I saw someone got a 3rd primary gear for around $38 au which is better than any US price (around $65) . I need a few other small bits and bobs as well so I have to finalise my list before ordering.

Cheers Rileyp

Yeah man whatever floats your boat!!

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