ASK THE MXPERTS: JETTING FOR THE 2007 YZ450F

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Dear MXA,
Could you provide me your jetting specs for 2007 YZ450F? I was told by a bike shop mechanic that Yamahas are typically delivered by the factory with too small a pilot jet. Is this your experience?

No, it isn’t. The jetting on the 2007, 2008 and 2009 YZ450F are all the same. We did change the pilot jet in 2006, but from a 42 to a 45—and the 2007-09 YZ450F’s came with a 45 after that. On the 2007 YZ450F, we ran the stock 160 main, 45 pilot, 55 leak jet and the fuel screw 2-1/8 turns out. The stock 2007 NFLR needle is a half-clip leaner than the optional NFPR needle. This was done because the 2007 YZ450F had a smaller outlet on the muffler. If you switched to an aftermarket exhaust, you could return to the NFPR, richen the clip one position or go to a 165 main.

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