I downloaded the animation pack from here: https://www.assetstore.unity3d.com/en/#!/content/25794 The assert contains a fbx file, which contains a bunch of animations.
Then in Animator window I added a State and transitions between states and have set the Motion in the inspector of the state. Then I look at the preview in Animator's inspector with it original Model, the animation works properly:
If I apply Unity Model or my custom Model in the preview, its became:
Why is that? How can I fix it? Or did I use it incorrectly?