Elevation ?

[roofer dude]

Would 600' lower elevation change jetting in 2003 YZ450? If so what would changes be ? ?

[YamaLink]

Properly jetted, I can go from 2800 ft upwards of 6000 (give or take) with minor adjustments to the fuel screw.

[BBrown626]

Would 600' lower elevation change jetting in 2003 YZ450? If so what would changes be ? ?

It could. Jet for the altitude, temperature, humidity, etc. The air is denser at a lower altitude so opening the fuel screw a bit may fix it, or if other conditions changed you might need to rejet. I normally go from 1400' to sea level with no significant issue, but each bike is different and you might be lean already.

[grayracer513]

If 600 feet makes any difference, it's because your current jetting is wrong. I run the same jetting from 100 feet below sea level to just under 4000 feet, changing the main twice a year to adjust for the seasonal temperature changes. They just aren't that sensitive to it.