Jet bike is not moving forward.

Okay, so I'm making a jet bike game and I was having trouble with the terrain collision. I realized I was using Translate, and switched to using forces. Now my Character isn't moving forward. My character, by the way, is an empty parent with a number of various 3d objects and a camera for the children. All have Rigidbodies that use gravity and are Kinematic. Otherwise, the whole thing falls apart. Terrain does not have a rigidbody nor a collider. Code follows.

`using UnityEngine;

using System.Collections;

public class PlayerController : MonoBehaviour {

public float Speed;

private Rigidbody rb;

public float RotateSpeed;

void Start() { rb = GetComponent(); }

 void FixedUpdate (){
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical") * Speed;
     float rotateHorizontal = Input.GetAxis ("Horizontal") * RotateSpeed;
     Vector3 movement = new Vector3(moveVertical,0f,moveHorizontal);
     rb.AddForce(movement);
     transform.Rotate (0f,rotateHorizontal,0f);
     

}

}'