A little more snap for my WR400

7 replies to this topic
  • pdrides

Posted May 04, 2008 - 07:01 AM


My '99 WR400 runs great, no bog, plug looks good, starts easy etc.. But I would like to find a way of getting a litte more snap/crispness when I'm at low RPM's and I goose it in 3rd or 4th. Right now the power kind of rolls on. It takes about as much time to get in the power band as if I were feathering the clutch. I'm running a White Bros. E2, my jetting is;
170 main
45 pilot
60 starter
200 main air
75 pilot air
90 slow air
This is the set-up the bike came with except I changed from a White Bros E series to the E2. I didn't notice a change in performance when I switched exhaust so I figure the jetting was ok.
It's pretty much run like this since I've owned it so I don't know if this is just how they run or if somethings amiss.

  • tweav

Posted May 04, 2008 - 07:33 AM


you could change to yz cam timing.

  • maxtherat

Posted May 04, 2008 - 02:06 PM


+1 on the yz cam. Have you cut down the throttle stop and removed the grey wire? You can also do the o-ring mod on the accelerator pump linkage.

  • pdrides

Posted May 04, 2008 - 04:09 PM


Grey wire 's been snipped. I thought the AP mod was only if you were having problems w/ bogging.
When you say yz cam timing are you saying to just shift the chain to a different position on the cam sprokets or do you mean changing the cams?

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  • maxtherat

Posted May 04, 2008 - 06:49 PM


Either one. You can leave your stock exhaust cam in and just retard it one tooth(clockwise) or buy a cam for a 03 yz450 and get the benefits of more performance and the auto decompression feature. Hot Cams also makes a replacement cam as well. The o-ring mod will also help with slight performance gains as well. It's not just a fix for a bog. You did not mention if you cut down the throttle stop. That and the grey wire mod work together. Don't just remove it if you have not done anything with it. Cut it down or buy a stop for a yz.

  • Birdy426

Posted May 04, 2008 - 09:03 PM


Yup, do the YZ cam mod...450 cam if you can afford it, just timing if you can't. The power on either is great, and the autodecomp from the 450 cam is well worth the price of admission. Another thought might be a 13.5:1 Hi Compression piston. Finally, if you don't mind sacrificing some top end, go up a couple of teeth on the rear sprocket, or down 1 on the countershaft sprocket.

  • pdrides

Posted May 05, 2008 - 05:02 AM


Ok, I'll try the yz timing. Can't afford a new cam so I'll just have to keep walking around w/ my right leg bigger than my left for a while. I'm a little confused about the o-ring mod. From what I'm reading there are 2 different mods one is the o-ring and the other is the taffy. I'm guessing here but because I have and older fcr I need the Taffy...yes/no?

  • redswr

Posted May 05, 2008 - 12:03 PM


i got a quick turn throttle tube... made the bike real snappy untill i figured out i didn't have to turn it as much...lol. http://www.thumperta...ad.php?t=630642


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