03 Rebuild Tips or Tricks

3 replies to this topic
  • finthat

Posted March 19, 2009 - 05:21 PM


Hey guys just getting ready to rebuild my '03 yz450f. New parts that I am installing are a new Hotrods crank and rod along with a CP mid compression piston. The head, valves and cam are going to stay stock for this year. I have one concern about the cylinder, it has a bit of an edge worn at the top and bottom of the stroke. I have honed it but can still feel the lip at each end. Should I be concerned??? does it need to be re-plated? There is no flaking or other problems in the bore that I can see. I do not know the hours on the bike as I bought used in Dec. It will be used for trail riding and some mx track but I am by no means gonna be pushing the bike all out.


  • 642MX

Posted March 19, 2009 - 06:21 PM


I'd measure that cylinder if I was you. If you honed it and can still feel a ridge, the cylinder probably needs replated.

Also, don't forget to replace the oil pump & rotor while your at it, and replace the cam chain too. :)

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  • grayracer513

Posted March 19, 2009 - 09:33 PM


642 is right. The plating is a very thin layer, and if you can feel it, the wear is serious.

  • finthat

Posted March 20, 2009 - 10:34 AM


Thanks again guys. I am going to measure the bore on and off the ring groove and see how much wear there really is. I think there is about 5 thou of plating normally. So I will make my decision there.

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