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August12

03 YZ450F Top End Help

11 posts in this topic

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.

2003yz450f.jpg

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.

IMG_1161.jpg

IMG_1167.jpg

IMG_1173.jpg

Edited by August12

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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.

THOUGHTS.....

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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.

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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.

THOUGHTS.....

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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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.

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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

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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.

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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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