Intermittent ignition problems on Honda twins are often blamed on the coils, but the connection between the plug wire and boot is usually the real cause. This angled spark plug boot restores a reliable, water-resistant seal from your coil to the spark plug.
Over time, the original boots degrade, crack, and lose their seal — letting moisture in and electrons out. This replacement boot has stock appearance and features a water-resistant seal. The angled design is specific to the CB450, CL450, and CB500T — the cylinder head fins on Honda's vertical twin require a bent boot to clear properly. A straight boot can physically fit but sits snug against the fins. If you are working on a CB350, CL350, or CB360, you need the straight spark plug boot instead.
Difficulty: Beginner
If the boot does not seat on the plug: The spark plug has a removable terminal nut threaded onto the top electrode. Unscrew and remove it to expose the stud. See our terminal nut vs. terminal stud article for details.
This boot (3039) is angled to clear the cylinder head fins on the CB450/CL450/CB500T vertical twin. SKU 3009 is a straight boot designed for the CB350, CL350, CB360, and similar models where the plug sits in a more accessible position.
Two — one per cylinder. The CB450, CL450, and CB500T are twin-cylinder engines.
The spark plug has a removable terminal nut threaded onto the top electrode. Unscrew and remove the terminal nut to expose the threaded stud, then press the boot on. See our terminal nut article for details.
If the wire is cracked, brittle, or measures high resistance, yes. Trimming 1/4" of old wire before installing the new boot gives you a fresh connection point.
Last updated: March 2026
