Open Mixfile ReMixer, then Browse (in the upper right) and go to your motogp14 main directory, then select the GFX.MIX file.
Step 5: In Mixfile ReMixer click on Browse (this time right down) and choose Desktop. The tool extract the file GFX.MIX on the desktop. As it finish it should be a folder on you desktop named GFX.
Step 6: Overwrite the GFX folder with the one you downloaded before.
Step 7: In Mixfile Remixer switch tab "create new mix file", then Browse (right up) and select the GFX folder from your desktop.
Step 8: Select from drop-down menu "SBK-XV8", then Browse (right down) and select the Desktop, then in the text box name the file GFX.MIX. It should create a new mixfile on the desktop.
Step 9: Copy the new file in your motogp14 folder and overwrite.