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Uponone420

450F vs 250F main jet comparison

3 posts in this topic

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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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.

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