yz 426f seized motor


32 replies to this topic
  • little-a

Posted January 25, 2011 - 08:29 AM

#1

Any help would be appreciated I have a 2000 yz 426f and I was out riding about 2 weeks ago an it sputtered then quit it had oil, coolant,and fuel in it but then when I tried to kick it it wouldn't budge any ideas????

  • honda98

Posted January 25, 2011 - 08:30 AM

#2

crank siezed up probley

  • little-a

Posted January 25, 2011 - 08:44 AM

#3

I'm not sure I haven't taken it apart yet. But I was wondering how to determine if its in the top end or the bottom. Any ideas?

  • brentn

Posted January 25, 2011 - 09:13 AM

#4

Won't really know until you pull the cylinder off.

  • KJK_JR

Posted January 25, 2011 - 09:16 AM

#5

you can check your oil filter for metal shavings. If you find bronze colored metal shavings that would be your crank. Also it could of jumped timing and bent a valve. You really cant be sure until you open it up.

  • little-a

Posted January 25, 2011 - 01:38 PM

#6

So basically I need to open it up an have a look before I will know anything at all? This is my first four stroker an I love it but I only gave a $1000 for it an I just can not see putting that much into it. Can I do the work myself I have the manual on it I just haven't read it much. Also if its only a piston seizure I'm assuming its just a cylinder bore an the a piston kit??? :thumbsup:

  • KJK_JR

Posted January 25, 2011 - 01:46 PM

#7

If you have the proper tools you'll be fine. If the cylinder is scored you cant just bore it cause it has a niksail coating so you would have to send it out to be replated which costs around $180.

  • brentn

Posted January 25, 2011 - 02:24 PM

#8

So basically I need to open it up an have a look before I will know anything at all? This is my first four stroker an I love it but I only gave a $1000 for it an I just can not see putting that much into it. Can I do the work myself I have the manual on it I just haven't read it much. Also if its only a piston seizure I'm assuming its just a cylinder bore an the a piston kit??? :thumbsup:


Your pretty much asking us which prize your going to get if you buy a cracker jack box... We have no real idea either until you open it up.

Your going to need tools, a service manual and possible new parts.
To the everyday jacknife mechanic who opens up a motor everything might look fine, but people who are doing things right need to check clearances. If you've never done a top end on any kind of motor before, this is going to be a whole new experience to you.

I would start reading the manual on the engine, and look at all the pages that correspond to removing the top end and splitting the cases right down to the transmission. After reading that over enough you will know what you are getting yourself into, you'll know what tools you'll need and you'll have a better idea of how much this is going to cost.
If it all seems like just way to much bring the bike to a dirtbike mechanic that's reputable and pay him for his time to diagnose the issue...

  • zukboy789

Posted January 25, 2011 - 02:28 PM

#9

Im sorry to say, but i can bet its the crank bearings. These bikes were notorious for having them go out.

  • little-a

Posted January 25, 2011 - 04:43 PM

#10

Thanks for the help fellas. I'll pull the top end this weekend and post what I find.

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  • pembell

Posted January 26, 2011 - 04:22 AM

#11

Before doing anything too drastic, check that the cam chain hasn't jumped on the cam sprockets. That will 'seize' the kickstarter.

  • little-a

Posted January 27, 2011 - 06:27 AM

#12

Ok I'll let ya know what I find. Thanks for the input.

  • little-a

Posted February 02, 2011 - 04:55 PM

#13

Well I checked my cam chain its not there so my next step is to take the jug off.

  • brentn

Posted February 02, 2011 - 06:20 PM

#14

cam chain was not on the cams, is that what you said?

  • pembell

Posted February 03, 2011 - 02:21 AM

#15

cam chain was not on the cams, is that what you said?


:thumbsup:

....well...that'll cause a seize alright.....

  • little-a

Posted February 04, 2011 - 05:55 AM

#16

Sorry about that I meant its not out of time or bunched up between the cams. So I plan to pull the jug this weekend. I'm hoping its the piston but I figure with my luck its gonna be the crank bearings......at this point I'm kinda wishing I had bought a two stroke at least I would have an idea what I'm doin!!! Lol

  • pembell

Posted February 05, 2011 - 05:57 AM

#17

Good luck!

  • KJK_JR

Posted February 05, 2011 - 08:03 AM

#18

Sorry about that I meant its not out of time or bunched up between the cams. So I plan to pull the jug this weekend. I'm hoping its the piston but I figure with my luck its gonna be the crank bearings......at this point I'm kinda wishing I had bought a two stroke at least I would have an idea what I'm doin!!! Lol


once the head is off everything is pretty much the same as a two stroke. Just follow the manual and be sure to use all torque specs when reassembling. Take your time and be gentle dismantling it and you'll be fine.

  • little-a

Posted April 26, 2011 - 10:14 PM

#19

So i finally got started disassembling my bike and so far nothing unusual. But i found a wr450 motor that is complete and runs does anyone know if i can swap it out for the original?? Once again thanks for the help.

  • banda

Posted April 27, 2011 - 04:29 AM

#20

I don't know any better than anyone else what's wrong with your bike, but the symptoms are much like when my connecting rod bearing was munched on my '00 426.

I replaced the whole crank assembly with one from a 2002 426, because it has splines for the counterbalancer drive gear instead of the stupid key I had to keep replacing.

It was scary to split the cases and pull the transmission out, but I managed to do it, and get it back together and running with no leaks or odd noises.





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