02' WR426 lost 3rd Gear

Has anyone out there ever replaced a gear on there 426. If so whats entailed and how hard is it? While coming off a jump, my third decided to fail. A mechanic rode and said its gone. He said i would have pull out the motor(which i have), pull off the head and split the case. It was to my benifit to do it myself as this would have cost $600.00 in labor. I'm actually considering getting rid of the bike and getting a slightly used one as the cost-to-benifit ratio puts me in a bind. Any advice would be appreciated.

Can I have the old bike since you wont be needing it anymore. :thumbsup:

Just get the factory manual and it will walk you through it. It's really not that hard to split cases on a dirt bike. Just pay close attention to everything you take apart! Using a digital camera to take some shots of what things look like before you tough them. Labling always helps too

I've never done it, but a buddy of mine rebuilt his transmission a while ago. He said it wasn't too bad. Order the parts and give it a shot. I don't know if you have a ton to lose at this point.

Easy enough - here's a pic of what my insides currently look like (I blew a bearing). Decided to replace all the bearings, am also replacing 2nd and 3rd since they have some wear, fresh rings, honed cylinder, new timing chain - the gears are cheap, so go and fix it yourself, it's easy if you have basic mechanical skills and some typical tools. (yes, you'll need some beer too)


wow still looks like lots of bits to me :thumbsup:

oh well hopefully i will not be pulling mine apart for a while yet :ride:



As mentioned above the key is to take note of everything before you take it apart. The only part I had real dramas with (i recently replaced 5th) was the order of the gears. Though I must admit, I s*&t myself when I first split the cases when i saw how much was in there! But it's not as bad as it looks.

I just finished rebuilding my '03 WR450. It only takes a few hours (3-6 depending on beer consumption) to get it all apart. I had several plastic containers that were clearly marked as to what was in there. I didn't think the guy at the Yamaha shop (not a certified mechanic) knew any more than i did, so i dove right in. Great experience! Pay attention to where the dowels go when sepatating the cases. I did the starter clutch, all the bearings, crank, piston, wrist pin, rings, timing chain, plug, third pinion gear and cam circlip (thing that started my having to rebuild). Now she really hauls balls! Use the manual like your Bible, and you'll have very few, if any problems.:thumbsup:



2 hammers 2 beers 2 screwdrivers and an impact gun, all in a good days work matt

AHEM!!! Cough Cough - that's THREE beers (upper left corner)!

Funny how the tools on/around the bench really don't reflect the job at hand (although I must admit - those screwdrivers did split the case).

Just an update, got my OEM parts last week, threw the gears and axle together, BBQ'd the cases for the bearing install - like butter, dropped the tranny in Friday night - had to use the BBQ again to get the crank in the left side since I didn't have a puller - dropped right in again, heated the right case before my morning coffee at 6am Saturday and zipped it up by 6:15am, got a coffee, installed the gears, clutch and everything else external to the case. waiting on my gasket/seal kit and I should have it running by the weekend if I get a few hours free time.

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