yz400 rod locked up on crank

1 reply to this topic
  • hardcore4x4_2000

Posted July 02, 2004 - 05:05 PM


My engine locked up on my 99 yz 400...after looking at what i need to buy I thought I might just go ahead an put a big bore kit in it. In the White Bros. catalog there is a note that says you have to re-coat the cylinder wall with Nikasil... WHY?... Its new ..right? Also can I just put a jug and a piston from a yz426 an basically get the same thing..in the aftermarket world the rods are differant but at yamaha the crank assy. are the same except the first three letters of the part numbers, I was told thats just the differants in years..CAN ANYONE HELP

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  • rsstom

Posted July 03, 2004 - 05:48 AM


As far as the big bore kit goes, WB sends a "remanufactured" cylinder and you send yours as a core that they will then prep for the next sale. That way there's no wait. You can buy a Wiseco piston and Cometic gasket set and send your cylinder to any of the good replating places such as US Chrome. They'll send it back ready to go.
The rod is different from 400 to 426. The wrist pin size is different. I think you could swap in the crank ass'y and cylinder as a set, but I don't know if it would be cheaper to rebuild your crank and bore your cylinder? For that matter, I think you could just use the 426 rod. Since you have to rebuild anyway.
Bottom line is: Big bore kit=400 rod and aftermarket piston and reworked cylinder.
426 kit=stock rod and cylinder and piston.

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