by JimDirt » Sun May 12, 2019 6:06 pm
Welcome to the site !!
I found this on another site doing a Google search
Hope this helps
Replace the main jet with a #158 main from the kit for riding from sea level to 4000 ft elevation.
***Note - Altitude:
Install the #155 main jet for riding mostly between 3000 ft and 6000 ft elevation and use the red marked needle in clip position #4 (middle).
Install the #150 main jet for riding mostly above 6000 ft and use the red marked needle in clip position #3 (3rd counted from top).
***Note - colder Temperatures;
Use the BLUE marked needle in the #4 position (middle) instead of the RED needle for cold conditions below 50F with 1 step larger main jet from the kit. The BLUE needle will richen the lower throttle range.
Air Filter Screen Removal:
If the metal air filter screen is removed, install the #160 main jit to compensate for the less restrictive airflow. There is a Twin air flame retardant filter for this purpose. This filter and the hondas "closed course" air box modification will allow use of a #165 main jet.2020 CRF450R
2006 CRF450X

Weiser , Idaho