Autodecomp. cam in a 99 yz400?????

10 replies to this topic
  • dmoney1074

Posted September 08, 2008 - 09:49 AM


I already read the sticky, and it says the 450 cam applies to the 400/426 model... but then it goes on to say that it works on 2000 steel valved , and 2001-2002 titanium valved heads. What about the 99? Is there something different that wont allow for the 450 cam?

Thanks all?

  • grayracer513

Posted September 08, 2008 - 10:02 AM


Yes, it works on YZ400's as well. There are also after market cams for YZ426 engines with auto decomp built into them. These will also work in a YZ400.

There are 3 principal differences between the AM and OEM cams:

> The OEM cam costs less. You can find them at TT OEM Parts and elsewhere for about $110

> The grind. The OEM 450 cam works very well with the original intake cam, producing what most describe as a wide, smooth, strong power curve. The AM cams will also work with the stock intake, but are often better in pairs.

> Timing procedure. AM cams for the 426 drop in and time just like the stock one. To use the OEM 450 cam, you have to get the intake cam timed first, and time the exhaust off of that. Not difficult, not even really tricky, just different.

  • dmoney1074

Posted September 08, 2008 - 10:08 AM


Thanks gray... I actually did the OE 450 cam on my old wr426, so I know all about timing it. I just needed to know whether or not it would work on the 400....

I just recently bought a yz250 after selling the 426, and i really regret it now. I HATE the yz for the type of riding I do... so I had a guy that was looking at my 250 offer me his yz400f plus like $500-600. It was supposedly fully rebuilt from the bottom up.... but you never know right?

Is there a big difference in the feel of the 400 when compared to the 426 (mine was a wr)? I LOVED my old 426....

One other question, besides the ss valves, and the bore size, is there any differences between the 400 and 426 motor?


  • pbviking

Posted September 08, 2008 - 10:16 AM


IMO I doubt you would notice a differance between a 426 to 400

Maybe a 400 to 450

I wished they made a bigger bore kit for the 426/400 20CC bigger Not even worth the time or money

  • dmoney1074

Posted September 08, 2008 - 11:05 AM


Gray, do you know if the lukes 444 kit works on the 400?

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  • grayracer513

Posted September 08, 2008 - 12:10 PM


Not unless you change the crank. The 426 has a larger wrist pin.

  • dmoney1074

Posted September 08, 2008 - 02:26 PM


Not unless you change the crank. The 426 has a larger wrist pin.

And as for the feel between the 426 and 400? Any discernible difference?

Thanks for the help! :thumbsup:

  • grayracer513

Posted September 08, 2008 - 02:31 PM


I haven't ridden that many 400's, and it was a while ago, but the YZ426 is stronger and lighter than the 400, probably enough of both to be noticeable.

  • dmoney1074

Posted September 08, 2008 - 02:41 PM


Okay thanks GRay... Im gonna consider trading for the 400 just because it will be more capable on the trail than my FIERCE yz250.... that damn thing needs to be on a track!

One more question.... I have a spare set of wheels for the 01 yz250... will they work on the 400? I thought I read somewhere the hubs are compatable from 97-02... but just to make sure?

  • grayracer513

Posted September 08, 2008 - 02:47 PM


The wheels from an '01 will fit a '99, but the rear won't swap to a '98, so be sure of what you're getting.

  • dmoney1074

Posted September 08, 2008 - 03:12 PM



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