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YZ 450 re-jetting

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What is the best jetting system for an 08 YZ 450F with an fmf factory 4.1 pipe? Looking for the best jetting specs for desert racing at sea level and high temperatures. :thumbsup:

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Stock jetting should be just fine.

In 2008 MXA said this:

 Q: HOW IS THE YZ450F JETTING?
    
A: No problems. Apart from spending a little time adjusting the fuel screw whenever the temperature or humidity changes, the YZ450F runs like a top.
The stock jetting is as follows:
Main: 160
Pilot: 45
Needle: NFLR
Clip position: Third from top
Fuel screw: 2-3/8 turns
Leak jet: 55
Notes: Yamaha also made MXA’s 2007 fuel screw settings standard on the 2008 carb. Last year it was 1-1/4 turns out. This year the stock setting is 2-3/8 turns out.

The real issue will be worn parts like the apump diaphragm, the slide plate seal, the emulsion tube (needle jet) and fuel screw oring (change to an R&D fuel screw).

Until you change those wear components, it will be difficult to get it to run like new.

The new pipe might  need the needle to go up one postion.

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