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Harry_in_Oz

YZ/WR timing

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After or rather during last weekends ride I changed back to WR timing. Having tried both I'd say it's likely that a well tuned WR is faster anywhere than a YZ. The YZ has more midrange power without doubt, but it lacks the spread and versatility of the WR. I'd say that the YZ may feel faster than a WR and give a rush with the midrange power but little more. For trail work you might as well be riding a two stroke, and it would be lighter. I know that you would rather I said what I really think but hey! it's a family site.

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Harry - how long did you ride it with WR timing, and how long with YZ timing?

Do you think you had it jetted correctly in both cases ?

I ask because I was about to make the change to YZ timing, but I've been hesitating because of exactly what you reported. I've always loved the fun to ride mid-range hit of the 250's I've ridden for years. But then I've usually tuned them for the low-mid grunt and smooth power because that's what turns the fastest laps and is the least fatiguing.

From the many volumes of reports on this site, it sounds like I'd be trading a very smooth and strong low-mid motor (that I really like) for a possibly less efective yet harder hitting mid-top powerband - might be fun.

So what do you really think ? - Maybe peak HP is not always best ?

In the end, I will have to try the YZ timing just to end the curiosity...since I already bought the jets.

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I read on a another forum site (DRN) that this timing change can kill your lugging ability. Since we ride in many rocky/technical areas and have been completely spoiled by the powerband of 4-strokes, I worried about making this change. The writer also mentioned adding teeth to the rear sprocket and increasing back pressure could solve the loss down low. Do you have any comments?

------------------

<u>Jake</u>

Denver, Colorado, USA

'99 WR400F

'95 XR600R

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Does anyone know where I can find info on the net about changing the timing from YZ back to WR. I know someone that would be very apprecative of this information. (he bought his WR400 with the timing set to YZ) Thanks! :)

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Use links to go to the Australian thumper site. Then WR400 tech. Open WR/yz timing.

This describes the WR to YZ process in terms of the number of cam chain pins between two marks on the cam sprockets. Print it out and follow it through without actually changing the timing. Then work through backwards to end up with 13 chain pins betwwen the marks, you will start with 12. Just be sure to lock the cam chain tensioner "off" so the chain is quite loose. When you go to lift the cam shaft cap off be aware that there is a bearing retainer under the cap. It can fall out and drop into the guts. I grab it with a magnetic rod as I lift. Otherwise lift the cap off and AWAY from you so it falls where you can get it. It is a good idea to stuff clean rags into the space used by the cam chain under the cam shaft sprockets. Clark suggests removing the cam shafts and recording the numbers on the shims while you are in there. It helps later. If the cam chain tensioner is off properly you should be able to rotate the exhaust cam sprocket without much trouble. You may need to have someone hold tension on the screw driver in the tensioner. Thats about it.

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