YZ400f engine swap to a 426f

8 replies to this topic
  • 250stroker

Posted December 05, 2010 - 09:27 AM


hi guys, i have a 98 yz400f and the top end blew at the dunes this past summer. The piston rod broke and smashed a hole through the side of the jug and took a chunk out of the crank case. Parts for this motor are $$$$ s and i cant fing any 400f motors online. i'm wondering if i can just put a 426 motor in there. as far as i know it will fit but i'd like some more information before i go spending more $$$$. thanks!

  • grayracer513

Posted December 05, 2010 - 09:55 AM


As I recall, the '00 and '01 will bolt in, but the '02 won't because of the swing arm pivot being larger.

  • 250stroker

Posted December 06, 2010 - 10:33 AM


is the carb the same for both? how about the electrical? thanks

  • grayracer513

Posted December 06, 2010 - 11:04 AM


Both the '00 and '01 used the same model carb and the same electrics.

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  • MXjunkie59

Posted October 21, 2011 - 01:53 PM


got a 98 YZ400F
New top and and it runs good... it BLOWS coolant out the over flow from the radiator but has NO liquid in the oil????
changed Radiator cap twice now... what the heck is wrong??? and should I just swap it out for a 426 or??? and is an 02' the newest that will swap out with no mods...
....... I need some advil and a beer!!!!!!!!


Edited by MXjunkie59, October 21, 2011 - 02:11 PM.

  • grayracer513

Posted October 21, 2011 - 05:17 PM


....... I need some advil and a beer!!!!!!!!

So how does that separate you from the pack? :thumbsup:

You can have a head gasket leaking in such a spot that it doesn't foul the engine oil. You can also have clogged radiators that don't cool. Or you can stand at idle for 5 minutes and make a perfectly healthy 400 blow coolant.

If your radiator has pressure in it almost immediately (please be careful around hot radiator caps), it's probably a head gasket.

  • MXjunkie59

Posted October 21, 2011 - 08:06 PM


I was thinking blocked water jacket or head gasket... start the bike open the choke, rap it a couple of times then blast through 1st, 2nd and third... shoots out and straight solid stream of coolant ..... three or four blast through the gears like that and the radiator is almost 3/4 empty............

So how does that separate you from the pack?


  • jojo1224

Posted October 21, 2011 - 09:40 PM


If you remove the rad cap and slowly kick it over and see bubbles coming up, well 95% of the time that means your head gasket is blown.

  • MXjunkie59

Posted October 21, 2011 - 09:42 PM


Thanks dude!!

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