ISO YZ426f Catastrophic failure help


12 replies to this topic
  • PNW Thumper

Posted May 23, 2016 - 09:20 AM

#1

Hopefully someone has some info or a place to turn for what I'm dealing with. I have a 2000 426, and a couple weekends ago while riding up a long gravel road my bike started to lose power under mild throttle. As soon as I noticed it, I started slowed down just in time for the bike to shut down on me as soon as I pulled the clutch in. When I tried to kick it over, I realized it had seized!!!


Well, after tearing the top end down I found that the connecting rod bearing had failed and there was some scoring on the piston and cylinder walls.

Upon doing some searching I found that there isn't a whole lot of options for the 426 when it comes to rebuilding them. Aside from OEM parts, I only found one company that makes a connecting rod kit and they're out of tapai, Taiwan... F that..

It looks like the crank is pressed together so, I'm guessing I have the option to buy a new pin and con rod, and have it pressed but when pricing out OEM stuff, it quickly got very expensive.

I'm in need of a crank kit, or a connecting rod kit, cyl and piston. Anyone know any big bore options or bottom end kits available??

ImageUploadedByThumper Talk1464024019.112390.jpg ImageUploadedByThumper Talk1464024042.179268.jpg ImageUploadedByThumper Talk1464024056.361100.jpg

  • grayracer513

Posted May 23, 2016 - 10:19 AM

#2

Top end wise, your least expensive option is to re-plate the cylinder and assemble it with a new OEM piston and rings, which will also result in the most reliable top end you can put on the bike, not coincidentally.

 

As far as the crank goes, see if you can still get a complete crank from Hot Rods for an '01 or '02 model.  They should still have them, and their quality is near OEM levels at a price that's usually below the cost of a rod kit and a rebuild on yours.  To use the '02 crank, you'll need to use the crankshaft balancer drive gear from an '01-'02 as well, as the gear was changed from a keyed index to splines in '01. 



  • PNW Thumper

Posted May 24, 2016 - 11:20 AM

#3

Awesome thanx for the info and links! I did a little research and calling around and cranks aren't available. Just the rod kit(from what I found at least). I also found a machine shop here in town that'll pull the crank apart and press the new pin / rod. He said he did plating as well but it was $280 and I found an OEM new cylinder from Yamaha for $279 so it seams that is probably the better option. As far as my piston, should i get my new cyl first to make sure I get the right size piston or because it's going to be OEM don't worry about it and get the STD bore?

  • grayracer513

Posted May 24, 2016 - 11:33 AM

#4

There is only one size OEM piston.  If using a new OEM cylinder, they fit like they were made for each other.



  • PNW Thumper

Posted May 24, 2016 - 04:05 PM

#5

I was going to go with a wiesco

  • grayracer513

Posted May 24, 2016 - 08:26 PM

#6

That wouldn't be my choice.  The OEM part is a high quality forged piston with an outstanding record of reliability.



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  • PNW Thumper

Posted May 25, 2016 - 12:17 PM

#7

Good to know. Thanks for the info!!

  • 0bigsilver6

Posted May 25, 2016 - 05:28 PM

#8

Agree with gray. I just did my top end in my 02, went with a wiseco piston and wish I had used oem. The wiseco has quite a bit of piston slap when cold, pretty annoying. Next time I will absolutely be going with oem.

  • mike_dean

Posted May 29, 2016 - 07:39 AM

#9

The Wiseco runs an extra .001" of clearance, knocked in my 426 for 150hrs till I put in an OEM.



  • 0bigsilver6

Posted May 29, 2016 - 09:58 AM

#10

The Wiseco runs an extra .001" of clearance, knocked in my 426 for 150hrs till I put in an OEM.


It didn't put any extra wear on the cylinder did it? That's the only thing that worries me about leaving it in for a long time and then trying to go back to oem.

  • mike_dean

Posted May 30, 2016 - 03:00 AM

#11

No, put the OEM piston in and noise was gone, cyl showed no wear or scoring and measured in specs.

  • mike_dean

Posted May 30, 2016 - 03:05 AM

#12

You are right about oem cyl. A friend rebuilt an '03 yz250f and got a new cyl for $251

  • toten

Posted May 31, 2016 - 06:04 AM

#13

Top end wise, your least expensive option is to re-plate the cylinder and assemble it with a new OEM piston and rings, which will also result in the most reliable top end you can put on the bike, not coincidentally.

 

As far as the crank goes, see if you can still get a complete crank from Hot Rods for an '01 or '02 model.  They should still have them, and their quality is near OEM levels at a price that's usually below the cost of a rod kit and a rebuild on yours.  To use the '02 crank, you'll need to use the crankshaft balancer drive gear from an '01-'02 as well, as the gear was changed from a keyed index to splines in '01. 

Sadly they no longer have complete cranks for 426s (or at least not on their web site). I checked every year and there's nothing. 

 

If the head is done, is there any advantage to using an early 450 head on a 426? I see an old post of yours that says the cylinder and head (as a combo) should bolt up.







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