yz426f help blown engine!!!! got pics


25 replies to this topic
  • bakeyz426f

Posted August 09, 2009 - 01:40 PM

#1

2002 yz426f broke a vavle and have the head off now. they said the crank rod could be bent. do i need to replace the cyilinder. where do i start and what parts should i get first. i got crank splitter, crank installer, piston puller, flywheel puller, clutch/flywheel holder, and valve compressor. do i need any other tools and where do i start on the bike. any help you can give me would be much apprecciated. i only got to ride her twice before she blew up.

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  • nickmell

Posted August 09, 2009 - 01:54 PM

#2

pull the cyl and see if it is scratched or damaged at all if so you need one. second you will need to see if the crank is wore, rotate it so th rod is at the top ifthere s up and down movement replace, third you will need new valves and everything that goes with the and maby a new head or you may be able to send your head to millennium technology and have them fix that one or just check on ebay for a new one, you will need a new cam chain and posibly cam to if it was damaged.

  • nickmell

Posted August 09, 2009 - 01:56 PM

#3

o and piston, rings and a gasket set

  • KaptainKoolz

Posted August 09, 2009 - 02:52 PM

#4

wow thats too bad...you could...get a new head(w/valves seals etc.)..might need new cyl..or bore and sleeve..new piston..rings..i would throw a new complete crank in...or you could find a working engine on cl/fleebay then part out your 426 trans..

EDIT: 666th post nnicee:devil: :thumbsup: :worthy:

  • bakeyz426f

Posted August 09, 2009 - 02:56 PM

#5

took off cyilinder it looks unharmed. what do u think.

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  • rmxtgh

Posted August 09, 2009 - 03:16 PM

#6

took off cyilinder it looks unharmed. what do u think.

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i think the seller sold the bike at the right time....!!:thumbsup:



that sucks though.....try the yz forum...you'll get better response....

  • yamaha king 69

Posted August 09, 2009 - 03:21 PM

#7

yea i would seriously be pissed if that was the second ride. thats why i would never buy a 4 stroke that old. good luck, hope you get it fixed soon!

  • bakeyz426f

Posted August 09, 2009 - 03:29 PM

#8

yea it didnt make me feel to dam good when she locked up it was bought new in 2005 im the second owner.

  • purplemonkeyparts

Posted August 09, 2009 - 07:37 PM

#9

Dude,
Once you fix it you will be a very very happy man. I love my 426 almost as much as my wife and truck. Just fix it and never worry about it. The 426 is a lot like a XR 400 just much much better.

  • matt4x4

Posted August 11, 2009 - 05:00 AM

#10

wow - that bike looks barely used - fix it and ride!!!!

Cylinder looks fine - make sure though - one pic can't make me 100% sure but it does look good.

To be honest - I wouldn't mess around, a hit like that on the valve is bound to transfer some unnecessary force to the bottom end, so I would get a new crank/bearings, and work my way up. I just buy cranks complete and balanced - saves a lot of trouble/headache and I don't need the specialty tools associated with truing a crank. As stated before, new timing chain, check your cams for damage to the lobes, maybe do the auto decomp mod while it's open if you need a new cam anyways, get the head cleaned up, drop in a set of kibblewhites and never look back - that bike will run for a long time.

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  • bakeyz426f

Posted August 11, 2009 - 01:16 PM

#11

my cams look alright to me. what do u think?
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  • The-Extractor

Posted August 11, 2009 - 02:39 PM

#12

the teeth look fine, you need to be more worried about the cam lobes. They should be near pefectly smooth with no scratches or nicks in them.

  • mxmaddman

Posted August 11, 2009 - 05:48 PM

#13

Check the lower crank sprocket for wear. Most likely this is a bike that the cam chain was never changed in and it jumped time. Either way it doesn't matter now. Head can be fixed, might be worth it just to buy a used head. quick rough estimates.

used head 300
head seat cutting 75
valve kit 325
piston kit 150
chain 30
gaskets 45

and some odds and ends, all assuming the cranks ok. Triple check the lower sprocket before it goes together again.

  • bakeyz426f

Posted August 11, 2009 - 06:03 PM

#14

is the lower sproket included in the crank assembly becase i was going to buy a new crank assemble. i think i going to send my head to millenium unless engine dynamics is cheaper. how much do u think it will cost to rebuild head and put valves in? millenium said 190 to repair head and couldnt give me a price on doing valves.

  • tp3dxf

Posted August 11, 2009 - 11:40 PM

#15

Tragic event really one of the first 426's I've seen do this. Bummer.

Were getting to that time when older WR's really have a lot of hours on them and need some love. It wouldn't surprise me to see more post like this in the future. Hey it did it's job for a lot longer then other thumpers do.

I have a 05 WR 450 and after seeing this post It will get some love soon. I'd rather replace parts that have life left in them then getting a grenade in the cylinder.

Fix her and ride again.

  • matt4x4

Posted August 12, 2009 - 05:35 AM

#16

center lobe on the intake looks a little rough on hte edges - could just be fuzz though...

To see if the gear spun on the cam - it's easier to see if they are installed...

  • mxmaddman

Posted August 12, 2009 - 05:42 AM

#17

is the lower sproket included in the crank assembly becase i was going to buy a new crank assemble. i think i going to send my head to millenium unless engine dynamics is cheaper. how much do u think it will cost to rebuild head and put valves in? millenium said 190 to repair head and couldnt give me a price on doing valves.


yea a new crank is a excellent idea. hot rod cranks can be found for $190.


repaired head 190
head seat cutting 75
valve kit 325
piston kit 150
chain 30
crank 190

you will have to buy the valves if you want to save money and assuming the guides are good it will cost 75 bucks to assemble and cut the seat from most places. I use mxtime.com for all my cutting. Milenium should be able to install them, ready to run for 75-$100.

  • bakeyz426f

Posted August 12, 2009 - 04:49 PM

#18

should i order valves before i ship out the head? millenium said they would get some for me. do u think that will cost me more if i dont get them before i ship head.

  • bakeyz426f

Posted August 13, 2009 - 01:50 AM

#19

what size hot rod crank fits the 426

  • Just_a_trail_rider

Posted August 13, 2009 - 02:16 PM

#20

Tragic event really one of the first 426's I've seen do this. Bummer.

Were getting to that time when older WR's really have a lot of hours on them and need some love. It wouldn't surprise me to see more post like this in the future. Hey it did it's job for a lot longer then other thumpers do.

I have a 05 WR 450 and after seeing this post It will get some love soon. I'd rather replace parts that have life left in them then getting a grenade in the cylinder.

Fix her and ride again.


I agree. this makes me nervous as well about my 05 wr450 which just seems to run and run and run with only the basic maintenance. No bike can really be this good, can it?

I've got no real odometer, but I would imagine that I've got around 5-6kmiles at most. I'll get a piston and timing chain (cheap) to try to avoid the "big bang" (if that's possible)




 
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