Jetting is driving me NUTS!!!

5 replies to this topic
  • Smokeslider

Posted May 21, 2006 - 06:36 PM


I bought a used 1998 yz400, the dealer said he jetted it for my elevation (4000 ft.), it's runs pretty well, he said to make sure I jet it for sea level if I go low elevation (800 ft. or so), so I bought a 175 jet from him which he said was best for low elevation, went to put it in today and the one that was in the bike was a 175!! So now I have 2 jets that are the same and I'm not sure what exactly I'm supposed to use for sea level!! Please Help!!

  • jwcrf05

Posted May 21, 2006 - 06:47 PM


175 is pretty high, i run a 165 in my 450 with a dr.d exhaust and I am right around 800 ft.

  • Smokeslider

Posted May 21, 2006 - 07:00 PM


yeah, I've got a fmf pipe on, thanks for the info

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  • Fastest1

Posted May 22, 2006 - 02:15 PM


Sounds fat to me. I would think 165-168.

  • kawirider

Posted May 22, 2006 - 03:26 PM


A better way to get answers to your question would be to describe what kind of problems you are having. Simply telling what jet size you currently have and what altitude you are at makes it pretty hard to give you any help.

  • DRH

Posted May 22, 2006 - 06:07 PM


i would start at stock settings. Bikes are usually jetted for sea level when new. I never re-jetted my 400. It ran good enough for me as it came to me. I am sure I could have benefitted for more precise jetting but to be truthful I don't think it slowed the bike down at all. I rode between 0-3500 ft

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