making a 400 into a monster

5 replies to this topic
  • amerrill130

Posted November 25, 2004 - 09:44 AM


Hey guys, okay i need a little help here. I have a 2000 WR 400, and i just love the bike. But i want more power so i have done all of the free mods except for the jet kit, i just have an fmf jet kit installed, but i want to get more power out of her. So my question to anyone is has anyone else been in the same situation? And what did you do. I have heard about the powernow system, that goes in front and back of the carb. But i was thinking maybe boring her out. I don't know. I rod my buddy's new 450 and love it, but can't afford to get a new bike. Can anyone else help me out. Thanks :cry:

  • Domenic_WRF

Posted November 25, 2004 - 05:53 PM


Power now is snake oil IMHO...Try JD's jetting before you do anything else, you will be surprised. Starting with YZ426 jetting with E-taper needles also will yeild the power increase you desire, but like me you may end up with a box full of jets and needles. JD's is plug n play, a good compromise, less work to dial it in. It will never run like a YZ450, but it will keep up with most 450's. :cry:

  • amerrill130

Posted November 25, 2004 - 06:48 PM


okay where can i get the JD kit at. Have you heard of anyone boring out the motor?

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  • ttr125smms120

Posted November 25, 2004 - 06:56 PM


yes im sure people have bored out their bike, and i believe you can find the jetting kit in the thumpertalk store although im not sure

  • Jethrro

Posted November 26, 2004 - 09:04 AM


Thumper Racing has some options on making a big bore out of the 400... somewhere around a 440. Never ran their products but have heard they are top notch.

  • Oasis_Flame

Posted November 30, 2004 - 07:55 AM


Option B;
You can do what I did. Mine is a 2000 Wr400 or was. I grabbed an 01' 426 jug and a Wiesco 13 to 1 piston made for the WR's. Do have p/n for the piston if your interested. I now have a monster. 2000 miles on this combo, no problems. :cry:


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