look at this head..


7 replies to this topic
  • yz00

Posted April 01, 2012 - 05:47 PM

#1

whatdo you guys think about this> I just boughtt the bike and was toldthe head gasket blew and sat in there rattling around and it wore the metal down a little in two spots where my fingers are. only visible damage i can see. the cylinder looks perfect as well as the piston. he said it ran before they pulled it apart. plan on laying down some jb weld and filing it down flat and putting it back together. i have a top end gasket set new.

Posted Image

Edited by yz00, April 01, 2012 - 05:48 PM.


  • Geoffit

Posted April 01, 2012 - 06:12 PM

#2

JB weld will not fix that issue you need to take it to good machine shop and have it surfaced. You will get an increase in compression which is ok, and if you really want to do it right the head needs to come completely apart and cleaned and checked.

  • grayracer513

Posted April 01, 2012 - 08:29 PM

#3

That head may have to be welded before it can be surfaced. There's a limit to what you can take off. Looks like it ran with a bad gasket for quite some time.

  • yz00

Posted April 02, 2012 - 04:02 PM

#4

so how much could i have machined off before it wold become an issuee any iddeas?

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  • Geoffit

Posted April 02, 2012 - 07:07 PM

#5

well on a 450 you can take .020" (.5mm) with no issues I'm guessing that is a 426 head? can't say for sure on those, a good shop can look at the craters and tell what it will need, If you weld the valve seats will need to be cut for sure ( if they don't already)

  • yz00

Posted April 03, 2012 - 06:25 PM

#6

ok so im going to end up sending it out to be milled. its a 98 yz400 any other motor mods worth while doing while its apart? :thumbsup:

  • Geoffit

Posted April 04, 2012 - 06:02 PM

#7

well it is a 13 year old dirt bike you can't go wrong replacing every thing you can afford to do. that being said how much do you put into a bike that old??? the bottoms are pretty tough it looks like it was not burning too much oil so fix the head and run it, be aware that the bike ran pretty hot for awhile to do that much damage to the head. Shows how tough the bikes are. Any way you look at it it's a pay now or later type of deal how much later is the bet........

  • Gunner354

Posted April 04, 2012 - 06:51 PM

#8

well it is a 13 year old dirt bike you can't go wrong replacing every thing you can afford to do. that being said how much do you put into a bike that old??? the bottoms are pretty tough it looks like it was not burning too much oil so fix the head and run it, be aware that the bike ran pretty hot for awhile to do that much damage to the head. Shows how tough the bikes are. Any way you look at it it's a pay now or later type of deal how much later is the bet........

Time to part it out and upgrade to an 08 or newer YZ. You will be amazed how much better the newer bikes are.





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