If your dirt bike is running at high RPM continuously after installing a new throttle cable, there could be a few potential reasons for this issue:
Incorrect Installation: Double-check the installation of the new throttle cable. Make sure it is properly routed and adjusted according to the manufacturer's specifications. If it is installed incorrectly, it could cause the throttle to be stuck in the wide-open position.
Binding or Pinched Cable: Ensure that the throttle cable is not binding or getting pinched anywhere along its path. A binding or pinched cable can prevent it from returning to its idle position, resulting in the high RPM.
Misaligned Carburetor or Throttle Components: Verify that the carburetor and throttle components are correctly aligned and functioning properly. If they are misaligned or improperly adjusted, it can lead to the throttle being stuck open.
Damaged or Defective Throttle Cable: Examine the throttle cable for any signs of damage or defects. If the cable is frayed, kinked, or stretched, it may not be able to properly control the throttle, causing it to run at high RPM continuously.
It is recommended to carefully inspect the throttle cable, throttle assembly, and carburetor to identify any issues or misalignments. If you are unsure or unable to diagnose and fix the problem yourself, it is advisable to seek assistance from a professional mechanic or an authorized service center for further inspection and repair.