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Yz250 jetting?


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I just bought new exhaust(fatty pipe and procircuit scilencer) and boyesen pro series reed valves for my 2003 Yz250 and was wondering if i need to rejet it and to what jet size? any help would be great. Thanks

Edited by fastyz250
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I recommend you upgrade to the 2006+ N3EW needle 2nd clip, drop the main and pilot one size (175 MJ 48 PJ), fuel screw ~2 turns out (also Pro Circuit's rec). Worked great on my 03 YZ 250 with Boyesen reeds and Pro Circuit platinum pipe (virtually identical to the Fatty) or 06 stocker, and several friends' 06+ bikes with various pipes.

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