HoverBike rotation return Y axis to 0

Hello everyone, i don't know how to resolve this problem :

I am making a HoverBike and took the basic hovering script with raycast, i tried to tilt the object when it turns but then the car would not rotate, so i tried to make another way to rotate but then i noticed that when i release one of the horizontal key, the object's Y Axis simply return to 0, slowly. This effect suit perfectly the tilting rotation, but also apply to turn rotation wich make my Object impossible to control. I am relatively new to unity so i may have made rookie mistake, and for that i apologize. Thanks you.

New HoverScript :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class HoverMotor : MonoBehaviour
 {
 
     public float speed = 90f;
     public float turnSpeed = 5f;
     public float hoverForce = 65f;
     public float hoverHeight = 3.5f;
     private float powerInput;
     private float turnInput;
     private Rigidbody surreaRigidbody;
 
     void Awake()
     {
         surreaRigidbody = GetComponent<Rigidbody>();
     }
 
     void Update()
     {
         powerInput = Input.GetAxis("Vertical");
         turnInput = Input.GetAxis("Horizontal");
         
     }
 
     void FixedUpdate()
     {
         Ray ray = new Ray(transform.position, -transform.up);
         RaycastHit hit;
 
         if (Physics.Raycast(ray, out hit, hoverHeight))
         {
             float proportionalHeight = (hoverHeight - hit.distance) / hoverHeight;
             Vector3 appliedHoverForce = Vector3.up * proportionalHeight * hoverForce;
             surreaRigidbody.AddForce(appliedHoverForce, ForceMode.Acceleration);
             
         }
         
         surreaRigidbody.AddRelativeForce(0f, 0f, powerInput * speed);
 
         if (turnInput < 0)
             transform.Rotate(-Vector3.up * turnSpeed * Time.deltaTime);
         else if (turnInput > 0)
             transform.Rotate(Vector3.up * turnSpeed * Time.deltaTime);
     
 }

Old HoverScript :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class HoverMotor : MonoBehaviour
 {
 
     public float speed = 90f;
     public float turnSpeed = 5f;
     public float hoverForce = 65f;
     public float hoverHeight = 3.5f;
     private float powerInput;
     private float turnInput;
     private Rigidbody surreaRigidbody;
 
     void Awake()
     {
         surreaRigidbody = GetComponent<Rigidbody>();
     }
 
     void Update()
     {
         powerInput = Input.GetAxis("Vertical");
         turnInput = Input.GetAxis("Horizontal");
         
     }
 
     void FixedUpdate()
     {
         Ray ray = new Ray(transform.position, -transform.up);
         RaycastHit hit;
 
         if (Physics.Raycast(ray, out hit, hoverHeight))
         {
             float proportionalHeight = (hoverHeight - hit.distance) / hoverHeight;
             Vector3 appliedHoverForce = Vector3.up * proportionalHeight * hoverForce;
             surreaRigidbody.AddForce(appliedHoverForce, ForceMode.Acceleration);
             
         }
         
         surreaRigidbody.AddRelativeForce(0f, 0f, powerInput * speed);
         surreaRigidbody.AddRelativeTorque(0f, turnInput * turnSpeed, 0f);
     
 }

TiltScript:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class TiltScript : MonoBehaviour {
 
     private float tiltAngleVertical = 5f;
     private float tiltAngleHorizontal = -25f;
     public float tiltRes = 5f;
 
     // Use this for initialization
     void Start () {
         
     }
     
     // Update is called once per frame
     void Update () {
 
         float tiltAroundZ = Input.GetAxis("Horizontal") * tiltAngleHorizontal;
         float tiltAroundX = Input.GetAxis("Vertical") * tiltAngleVertical;
 
         Quaternion target = Quaternion.Euler(tiltAroundX, 0, tiltAroundZ);
 
         transform.rotation = Quaternion.Slerp(transform.rotation, target, Time.deltaTime * tiltRes);
     }
 }