02 426 overhaul, what should I look for?


3 replies to this topic
  • fritzelman

Posted February 29, 2008 - 09:14 AM

#1

I've finally talked myself into swapping out the YZ gears for WR ones in my 02 426. Is there anything I should look for while I'm in there? Did these have anything prone to breaking down there, or on the way to the tranny? I was debating on doing a ring job while I had it torn down, good idea?

Also, if anyone has done this, do you need any special "yamaha" tools to get to the gears? Or just the basics?

Thanks

  • mkporn

Posted February 29, 2008 - 09:43 AM

#2

You can accomplish it with hmostly basic tools and creative thinking.

I would suggest replacing piston and rings, timing chain and main bearings while you have it split......Check to make sure the valves are good and not leaking and the faces are not beat.

pay attention to 3-5 shift fork for wear and being bent.

Wen you split it, pay close attention to the fact that between the cases there are a couple locating pins that act as oil passages and have an o-ring on them....make sure they go back where they are suppose to.

PM me and I can give you some tips to putting bearings in and also on tear down......

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  • 642MX

Posted February 29, 2008 - 04:57 PM

#3

I've finally talked myself into swapping out the YZ gears for WR ones in my 02 426. Is there anything I should look for while I'm in there? Did these have anything prone to breaking down there, or on the way to the tranny? I was debating on doing a ring job while I had it torn down, good idea?


I would replace the piston, rings, pin, cam chain, valve springs, valve seals, main bearings, rod bearing, and transmission bearings. Along with the counter-shaft seal, shifter seal and clutch actuator arm seal. Buy Yamaha gaskets too, the aftermarket brands just aren't the same quality.

Also, if anyone has done this, do you need any special "yamaha" tools to get to the gears? Or just the basics?


Yes, you will need the crankshaft removal tool and a flywheel puller. The crank won't come out of the main bearing without some 'force'. If you use a hammer, you'll destroy the end of the shaft and the threads on the flywheel side. With the tool, the crank can safely be removed from the left side case without damage. The crank tool retails for about $100. The flywheel puller is $10-15.

  • Birdy426

Posted February 29, 2008 - 06:17 PM

#4

You can also use a harmonic balance puller to push the crank out...and agree with ALL the bearings. It's hard to tell when they are really going bad...don't want to have to pull it apart again.





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