WR to YZ cam timing

I know that on the first several years of WR 400s, you could get YZ cam timing by rotating the exhaust cam 1 tooth clockwise on the timing chain. I also understand that new WRs require a new cam. My question is what year did we lose the ability to move the stock cam 1 tooth. I believe it was with the 450s. If so, would a 2002 WR 426 respond to moving the cam 1 tooth? Thanks

Yes, you can change the cam timing on your '02 - I did on mine. In stock condition, the WR has 13 pins on the timing chain between the intake and exhaust valves. To convert to YZ timing, change the spacing to 12 pins by rotating the exhaust valve. Hope this helps.

My question is what year did we lose the ability to move the stock cam 1 tooth. I believe it was with the 450s.
Yep, you are correct. With the 450's came auto-decomp.

98-02 yz/wr 400/426 have the same cams just different timing. 03-09 yz/wr450 have different cams.

Sorry to bump an old thread, but I guess that shows I searched before asking. :busted:

I know I don't have the stock exhaust cam in my 2000 WR400 because it has autodecomp (and the original is in a box). How can I tell that it's a YZ cam versus something else, and if it's a YZ cam do I still go with 12 teeth between cams or do I go with the original 13? I guess more specifically, how many teeth should be between the cams if you have a YZ exhaust cam?



Yay, Partsfish.com! I have the original box, and what I have is an exhaust cam from a 2004 WR450F -- SKU: 5TJ-12180-10-00

So, I guess I just go with stock timing? It looked somewhat "weird" when I took it out. I should have counted the links even though I have the book. :sigh:



Watch how you align the timing marks, they are not quite the same on the later model cam because the head is machined differently.

When I put the yz cam in my '98 I eye'd up the cam lobes from the '98 to the '03 and transfered the timing marks with a paint stick. I adjusted one tooth for yz timing and everything worked fine. You could probably do the same without the adjustment for yz timing.

Thanks for the reply, tcm.

So currently it's not starting, but that could be because it's super cold out there, even with the kerosene heater. What I ended up doing was I had the intake cam as it's supposed to be with the dot on the line from the head, and the exhaust cam I actually had rotated clockwise a bit so the lobes lined up correctly. Sound about right? In theory even if it was off by a tooth it should run albeit with reduced power.

The other nagging question is I never found a really great timing mark, even when taking it apart. The picture in the manual, and other marks I've seen on other bikes, is a very distinct vertical line. But on my WR, it's shorter, and really looks like the 'I' in "HI". This is right before an arrow, so what you get is "HI <-". I aligned on the 'I'. Is that correct?

Back to the garage to kick the thing some more. Wish me luck and let me know if you see something I did wrong. :busted:



Thanks, SXP. I finally found that, or specifically http://www.thumpertalk.com/forum/showthread.php?p=3706078#post3706078 the other night after doing more research. The pain of buying a bike that already has the mods is I end up having to do the research in reverse -- find out what I have, then why, and then how to adjust it! :busted:

I think that the problem is my exhaust cam is one tooth off, in the "will not run even though it looks correct" direction mentioned in that guide.

I'll give it another shot after the holidays.

Thanks everyone,


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