Note: This video is for the previous-generation HCD-1501. However, the principles of loosening the hook, re-timing and setting the gap are the same. Be sure on re-tightening the 3 screws on the neck of the rotary hook that the hook does not shift position. Hint: when re-tightening the sets screws, tighten gently at first, re-check timing and gap, then with more force once sure that the hook timing and gap are correctly set.
https://happyemb.com/files_maint/videos/rhtimevidHCD1501.wmv