2003 yz450f rebuild questions

4 replies to this topic
  • biggercb

Posted April 01, 2009 - 08:03 AM


I have an 03 I bought in '06. Had two previous owners, I have went through two back tires and two chains since I have had it. It was in really good condition with stock graphics and still really clean. I am debating on rebuilding the engine. Before I spend a huge chunk of change...do I need to? Estimating engine hours is hard, but I would guess maybe 100 hrs? Prolly less. I am not a racer, but I enjoy hauling tail when I do get the chance to ride. I ride maybe a dozen, two dozen weekends a year. Some sand dunes, mostly trails and the occasional practice day with my little brothers.

From searching and reading posts it seems they hold up pretty good..some guys loggin in tons of hours on these engines. I know a timing chain for sure...but piston? rings? valves?

Is worth to go through and spend several hundred on new everything? Or is it overkill to replace parts that still have life left?

Im just looking for opinions.

  • grayracer513

Posted April 01, 2009 - 08:55 AM


I had an '03 that had nearly 400 hours on it when I sold it, and had never had so much as a valve adjust.

But here's the problem that's always existed with this question:

You can recondition the engine preemptively, but to do so will certainly cost you the unused service life of whatever parts you replace. Will you "waste" 50% of the usable life of a piston? Or 5%? No way to know.

Parts that wear measurably, like cylinders and rings are one thing. They can be inspected and evaluated. Other parts, like rolling element bearings often fail suddenly, and in the case of a rod bearing, such failure can be catastrophic. Likewise Ti valves. They are exceptionally durable in YZF's, but when they reach the point where they start wearing through their hard coat, they are gone, then and there, and stretching their use farther invites the disaster of a dropped valve.

So your choice is to wait for something bad to happen and hope it's not too messy, or go through it at some time that you think is right, giving up some of the old part's service life in the process.

Nobody said it was simple.

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  • jjj109

Posted April 01, 2009 - 01:22 PM


if your not sure just pull it apart and do a top end. If you find anything else that needs to be taken care at the time then do it. :thumbsup: its cheaper and less time to do maintenance then to do repairs:bonk:

  • finthat

Posted April 01, 2009 - 04:59 PM


If you don't know or are not sure what the other guys have done to it(maintanace ect) I would take the topend off to have a look at least and judge from there. If it has signs of wear then you can got into the bottom end ect.

"When in doubt throw it out" kinda applies.

  • biggercb

Posted April 03, 2009 - 09:26 AM


Thanks for the replys

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