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Dirt Bike Brands - Other
Understanding jetting on 99 YZ400
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[QUOTE="Rich Rohrich, post: 119702, member: 16241"] Billy - 15% by volume of an oxygenate like MTBE will provide an 2.5% additional oxygen by weight. Given the square root realtionship between air density and fuel density it makes sense that this might be enough to get you in the ballpark. As you've found out these engines tend to be fairly insensitive to anything but major changes in atmospheric conditions. It's the advantage that comes from a high compression engine with a clean efficient combustion chamber and smallish high velocity ports and valves. Those Yamaha guys are pretty smart :) Sounds like you might be lean on the pilot circuit (most are). Depending on the fuel you can try turning the fuel screw out to about 2 1/4 to 2 1/2 turns for sea level to about 1000 ft and work up from there. [/QUOTE]
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Dirt Bike Discussions By Brand
Dirt Bike Brands - Other
Understanding jetting on 99 YZ400
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