03 YZ450F Top End Help

10 replies to this topic
  • August12

Posted November 29, 2011 - 03:45 PM


To Rebuild Or not to Rebuild

About a year ago I decided to redo my yz450. New plastic, Tires, Suspension, Pro tapers, Graphics...
Bike ran and looked the best it ever had.

Posted Image

This year the bike starts having a hard time starting cold. It gets worse and worse.
To the point that our last day riding in the desert i always pulled up to the top of the
hill so i could bump start it. Got it home tore it apart checked the valves and the
intake valves were closed tight and the exhaust valves were close to spec .17mm.
So re shimmed it put a new spark plug and fired right up.

I felt awww inside. This is my first time working on a four stoke. Grew up with two stokes...
hell of a lot easier.

Get out to Ridgecrest over turkey day and runs for about 30 min strong..
Come out of a corner and the bike just freezes up. So i walk it back to the trailer and park it..
Good thing i brought my extra bike 96 klx 650. What a pig but at least i got to ride.
So here is my delema. Now what to do.
I tore the head off and it looks like crap.. Pics below.

Posted Image

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Edited by August12, November 29, 2011 - 06:53 PM.

  • August12

Posted November 29, 2011 - 06:51 PM


Im thinking I'm going to need.

Kibble White Valves and Spring Kit
Wiseco HC Pisto 13.5:1
HotCams Stage 1 Intake/Exhaust
Chain Tensioner
Cam Chain

I really don't know what's wrong with it but figured this would cover it.


  • scrubbin627

Posted November 29, 2011 - 07:02 PM


Nice looking yz. It looks like some of the valves hit the piston, are you sure you shimmed it correctly?

  • August12

Posted November 29, 2011 - 07:09 PM


yah, Could the carbon build up had something to do with it. Also the plug i pulled out of it was just a ball of black. I wish i had the confidence to rebuild it before it was to late.
Now it might not be worth it.

  • blueberg17

Posted November 30, 2011 - 09:32 AM


Im thinking I'm going to need.

Kibble White Valves and Spring Kit
Wiseco HC Pisto 13.5:1
HotCams Stage 1 Intake/Exhaust
Chain Tensioner
Cam Chain

I really don't know what's wrong with it but figured this would cover it.


I'm guessing it still cranked over smoothly before you tore it apart? Can the crank rotate with the cylinder and head off? need more details...

You're spark plug was black? was it wet or dry? You may be burning oil...

I'd say do you're top-end rebuild if you have the money. Get an owners manual and just take your time.

At the very least ball hone the cylinder, put a new set of rings, and a new cam chain:thumbsup:

btw, nice looking bike!

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  • August12

Posted November 30, 2011 - 10:26 AM


Yah that is the plan. Rebuild ( slowly ) I think I'm going to pick up a newer mx bike for now.
And rebuild this into my desert bike. Can you put a baja kit on a 03 yzf450. Does anybody know how to do it.

  • August12

Posted December 01, 2011 - 04:59 PM


Found Baja Designs has some nice stuff. Looks like i just need a stator. Im going to pick up a crf. I was thinking a 2008 crf 450. the 09 sounds like they are small and to twitchy for the desert. Thoughts

  • grayracer513

Posted December 01, 2011 - 09:27 PM


I think you should ask for thoughts on the CRF in the CRF forum. The results would likely be based more on experience.

Personally, while I like a number of things about them, I don't think I can afford to own one.

  • WES11

Posted December 03, 2011 - 02:13 PM


Great looking bike but I think you should buy a CRF450r and slowly rebuild your YZF.

  • WES11

Posted December 03, 2011 - 02:16 PM


Take it to George @ ESP when you decide to rebuild. Good luck!

  • EGPeil

Posted December 14, 2011 - 02:23 PM


I have been converting an 03 YZ450F to desert for a Baja run (hopefully). I picked up an eLine stator from a TT user - they are the best option for the 03-05 YZ450Fs - 200w output. I also have a Baja Designs lighting kit which I'm told works very well with the eLine stator. I don't know if eLine is still producing those stators - the WR450 stators will not bolt onto the YZs without a crank and maybe more paraphernalia.

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