Why does the screw that holds the rotor on inside the distributor keep falling off. The times that it is running it backfires when I push in the clutch to shift gears?

The screw holding the rotor in the distributor may be falling off due to improper tightening or wear on the threads, which can prevent it from securing properly. Backfiring when you push in the clutch might indicate an issue with timing or air-fuel mixture, potentially caused by a misaligned rotor or a malfunctioning ignition system. It's essential to ensure the screw is tightened correctly and check for any other underlying ignition or fuel system problems. Regular maintenance and inspection can help prevent these issues from recurring.