450F vs 250F main jet comparison

2 replies to this topic
  • Uponone420

Posted April 06, 2009 - 09:09 AM


Hey guys, this is my first post so go easy on me. I am new to the 450f crowd moving up from a 2006 Yz 250f. When during research on jetting I noticed that the 450f runs a smaller main jet than the 250f. I understand the the 450 has a 2 mm larger carb, but isn't main jet sizing nomenclature the same for any fcr carb. Thanks in advance.

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  • grayracer513

Posted April 06, 2009 - 11:23 AM


Yes, all the jetting sizes, etc., cross the entire FCR platform. The 450 is a much bigger engine with a slightly bigger carb, and so has a significantly stronger vacuum signal drawing fuel through any of the jets. The stronger signal allows a smaller jet to be used to deliver the necessary fuel.

  • Uponone420

Posted April 07, 2009 - 06:30 AM


Thanks man!

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