I want to know the method of changing the bike's max turn value.

[emalafeew]

That solution only works if you also lean. If you want the bike rotation to just follow your head, then you can set it to the same rotation after VZPlayer.Update.

As an example you could subclass vzplayer and do like

override void Update () {
base.Update();
var angles = Controller.Head.eulerAngles
angles.x = angles.z = 0;
transform.eulerAngles = angles;
}