How to Replace Light Bulbs on a 2026 Harley-Davidson Street Bob (M8 117 / FXLSTS)

Harley-Davidson Street Bob M8 117 · 2026 · Light Bulbs

Light Bulb Replacement Guide: 2026 Harley-Davidson Street Bob (M8 117 / FXLSTS)

This guide covers every exterior light bulb position on the 2026 Harley-Davidson Street Bob (M8 117 FXLSTS), including the headlight assembly, front and rear turn signals, tail light, brake light, and running lights. The Street Bob is a bobber-style Softail powered by the Milwaukee-Eight 117 engine and retains a traditional dual-beam halogen headlight (H4) — unlike many modern Harley models that use sealed LED units — making bulb replacement straightforward and cost-effective for owners who prefer DIY maintenance.

Quick Reference Bulb Table

Note: The 2026 Street Bob uses traditional replaceable incandescent and halogen bulbs for most lighting positions, unlike the all-LED Sportster S. This means individual bulbs can be swapped without replacing entire assemblies. The headlight uses a standard H4 halogen bulb. Turn signals and tail/brake use standard 1157-series automotive bulbs.

Difficulty & Time Estimate

• Difficulty Level: Easy to Beginner (1 to 2 out of 5 — straightforward bulb swaps)
• Estimated Time:
• Headlight bulb: 10-15 minutes
• Front turn signals: 10-15 minutes per side
• Rear turn signals: 10-15 minutes per side
• Tail / brake light: 15-25 minutes
• Best Done: In a well-lit area with the bike on a stand or level surface

Complete Tool List

OEM Part Numbers & Aftermarket Alternatives

Note: The Street Bob uses standard automotive-style 1157-series bulbs for all tail, brake, and turn signal lighting. These are inexpensive and widely available at any auto parts store. The headlight uses a standard H4 dual-beam halogen bulb. When upgrading to LED, ensure the replacement is rated for 12V motorcycle use and has a compatible base (bayonet for 1157, P43t for H4). Consider adding load resistors or a flasher relay upgrade when converting turn signals to LED to prevent hyper-flashing.

Step-by-Step Instructions

Headlight (H4 Dual-Beam Halogen Bulb)

The Street Bob uses a 7-inch round headlight housing with a replaceable H4 (9003 type) halogen dual-beam bulb. The bulb is accessible from the rear of the headlight bucket without removing the entire headlight shell.

Step 1: Turn the ignition OFF. For safety, the Street Bob's battery is accessible under the seat area, though disconnecting is not strictly required — it is recommended.

Step 2: Remove the solo seat by loosening the mounting bolt on the rear of the seat base (typically a 5/16" hex key / Allen wrench). Lift the seat upward and backward to remove.

Step 3: Disconnect the battery negative terminal with a socket wrench to prevent any accidental short circuits or sparks.

Step 4: From behind the headlight, you'll find a circular weatherproof dust cap at the rear of the headlight housing. Pull the rubber dust cap off completely.

Step 5: Locate the retaining ring or spring clip that holds the H4 bulb in place. On most Street Bob models, this is a wire retaining ring secured by a Phillips screw or a spring-loaded clip on each side.

Step 6: Release the retaining ring or spring clips and carefully remove them. Set them aside in a clean, safe area — they are small and easy to lose.

Step 7: Gently pull the old H4 bulb straight out from the headlight housing. Do not twist aggressively — the H4 bulb has a keyed base to align it correctly.

Step 8: Critical: Put on clean nitrile gloves before handling the new H4 bulb. Never touch the glass of a halogen bulb with bare fingers. Skin oils create hot spots on the glass when the bulb heats up, causing premature and catastrophic failure.

Step 9: Align the tabs on the new H4 bulb's base with the slots in the headlight housing. The base is keyed and will only fit one way. Insert the bulb straight in.

Step 10: Reinstall the retaining ring or spring clips to secure the bulb. Ensure the bulb is firmly seated and does not wiggle. If using a retaining ring, re-tighten the Phillips screw to snug.

Step 11: Reinstall the rubber weatherproof dust cap over the rear of the headlight housing. Press it firmly around the entire perimeter to ensure a watertight seal.

Step 12: Reconnect the electrical connector to the rear of the H4 bulb. The H4 connector is a 3-prong spade connector (ground, low beam, high beam). Push firmly and verify it is fully seated.

Step 13: Reconnect the battery negative terminal and tighten securely.

Step 14: Reinstall the solo seat and secure the mounting bolt.

Step 15: Test the headlight: turn ignition ON and verify low beam operation. Toggle to high beam using the handlebar switch and verify it activates. Cycle through multiple times to confirm proper function.

Step 16: Aim the headlight beam (see Headlight Alignment section in Tips below).

Front Turn Signals (1157NA Amber Glass)

The Street Bob front turn signals are bullet-style signal housings mounted on short stalks. The bulb is accessed from the front of the housing by removing the lens bezel.

Step 1: Turn the ignition OFF.

Step 2: Locate the front turn signal that requires bulb replacement. The left and right bulbs are identical 1157NA units.

Step 3: From the front of the turn signal housing, use a #2 Phillips screwdriver to remove the lens bezel screw(s). On most Street Bob models, there is a single screw at the bottom edge of the bezel.

Step 4: Gently pull the lens bezel away from the signal housing body. Set it aside.

Step 5: Push the bulb gently inward while twisting it slightly counterclockwise. The 1157NA bulb mounts in a bayonet (BA15s) socket — push in and rotate counterclockwise to release.

Step 6: Remove the old 1157NA bulb and inspect the socket for corrosion or debris. Clean the socket with electrical contact cleaner if needed and dry completely.

Step 7: Take the new 1157NA bulb and align the offset pins on the base with the slots in the socket. Push the bulb in firmly and rotate clockwise until it locks into place.

Step 8: Reinstall the lens bezel over the turn signal housing and secure the mounting screw. Do not over-tighten — the lens bezel is plastic and the threads can strip.

Step 9: Repeat for the other side if replacing both front turn signal bulbs.

Step 10: Test: turn ignition ON and activate left turn signal — verify amber flash. Activate right turn signal — verify amber flash. Confirm both sides flash at the same rate.

Rear Turn Signals (1157)

The rear turn signals on the Street Bob are mounted on the rear fender in bullet-style housings matching the front. The bulb replacement process is nearly identical to the front signals.

Step 1: Turn the ignition OFF.

Step 2: Access the rear turn signals mounted on the rear fender brackets.

Step 3: From the front of the turn signal housing, use a #2 Phillips screwdriver to remove the lens bezel screw.

Step 4: Gently remove the lens bezel.

Step 5: Depress the old 1157 bulb and rotate it counterclockwise to release it from the bayonet socket.

Step 6: Inspect the socket and the wiring for any signs of moisture, corrosion, or damage. Address any issues before proceeding.

Step 7: Insert the new 1157 bulb into the socket — align the offset pins, push in, and rotate clockwise until it locks.

Step 8: Reinstall the lens bezel and tighten the mounting screw to snug.

Step 9: Repeat for the opposite side if needed.

Step 10: Test: activate rear turn signals and verify proper flash operation on each side. Check that the front signals also activate (both sides should flash together).

Tail / Brake Light (1157 Dual-Filament)

The Street Bob tail light is mounted on the rear fender underneath the solo seat area. It uses a single 1157 dual-filament bulb for both tail light (dim filament) and brake light (bright filament) operation.

Step 1: Turn the ignition OFF.

Step 2: Remove the solo seat by loosening the rear mounting bolt (5/16" hex key / Allen) and lifting the seat upward and backward. Set the seat aside in a clean area.

Step 3: Under the removed seat area, locate the tail light mounting hardware. The tail light lens is secured to the tail light housing with Phillips screws (typically 4 screws around the perimeter).

Step 4: Using a Phillips #2 screwdriver, remove all the lens mounting screws. Keep them with the removed lens assembly.

Step 5: Gently pull the red tail light lens away from the housing body. The lens may have a thin rubber gasket — keep it intact and set the lens face-down on a clean cloth.

Step 6: Locate the 1157 bulb inside the housing. It is mounted in a bayonet socket. Depress the bulb and rotate counterclockwise to release.

Step 7: Remove the old bulb and inspect the socket contacts for corrosion or darkening. If the contacts look dirty, clean them with electrical contact cleaner and allow to dry.

Step 8: Insert the new 1157 dual-filament bulb into the socket — align the offset pins on the base with the slot in the socket, push in, and rotate clockwise until it locks.

Step 9: Inspect the rubber gasket around the tail light lens. If cracked or deteriorated, replace the gasket to prevent moisture ingress.

Step 10: Reinstall the tail light lens onto the housing body. Align the screw holes and reinstall all Phillips screws. Tighten evenly — do not overtighten, as the lens body can crack.

Step 11: Reinstall the solo seat and secure the mounting bolt.

Step 12: Test all tail light functions: - Ignition ON: tail light should illuminate (dim filament — running light mode) - Front brake lever applied: brake light brightness should increase (bright filament) - Rear brake pedal depressed: brake light should activate - Turn signals active: verify that each signal overrides the tail light on the correct side (the 1157 bright filament is used for both brake and turn signal — they are combined by the wiring circuit)

Running Lights / License Plate Light

The Street Bob does not have a dedicated license plate light bulb. License plate illumination is provided by the downward light spill from the tail/brake light assembly and the lower filament (tail filament) of the 1157 bulb. When the ignition is ON, the tail filament of the 1157 bulb illuminates at low brightness, providing adequate license plate illumination.

If your license plate does not appear adequately lit at night: - Verify the tail filament on the 1157 bulb is functioning (the dim filament) - Check for proper tail light lens orientation — the lens should face downward toward the license plate - Verify the wiring harness connection at the tail light assembly — a corroded tail-filament contact will cause the license plate to go dark while the brake light still works

Tips, Warnings & Common Mistakes

Headlight Alignment After H4 Bulb Replacement

After replacing the H4 headlight bulb, verify proper beam aim:

1. Park the Street Bob upright on level ground, 25 feet from a flat wall or garage door. Use a rear stand (if available) or have someone steady the bike.
2. Measure from the ground to the center of the headlight lens.
3. Draw a horizontal reference line on the wall at the measured height. Draw a second line 2 inches below the first line.
4. With low beam active, the top edge of the bright zone (cutoff line) should be at or below the lower reference line.
5. The high beam center should be at or slightly below the upper reference line.
6. Adjust using the two alignment screws on the headlight mounting bracket — one for vertical and one for horizontal aim.
7. Tighten the adjustment lock nuts and re-verify.

Note: LED 7-inch sealed headlight replacements may have different beam patterns. If upgrading to an LED sealed headlight, follow the manufacturer-specific alignment procedure.

Halogen vs. LED Comparison

Turn Signal LED Conversion Notice

Important: When upgrading 1157NA or 1157 turn signal bulbs to LED, the reduced power draw may cause the turn signals to flash too quickly (hyper-flash). The Street Bob's flasher relay is designed for incandescent loads. To correct this: - Install a Harley-Davidson LED-compatible flasher relay (OEM part varies — check with dealer for 2026 Softail platform) - Or install load resistors (5-ohm, 10W minimum per direction) in parallel with each LED turn signal - Or use a programmable aftermarket flasher module

Diagnostic Tips

• Headlight not working: Verify the H4 bulb connector has power at all 3 terminals (ground, low beam, high beam) with a multimeter. If no power, check the main fuse under the seat.
• One turn signal works, other doesn't: Before replacing the bulb, check the wiring from the turn signal housing to the main harness. The bullet-style stalk wiring is prone to chafing where the wiring exits the mount.
• Tail light works, brake light doesn't: The 1157 bulb has two filaments. The bright filament may be blown while the dim filament remains intact. Replace the bulb.
• Tail light dim or flickering: Check for corrosion in the ground connection. The tail light grounds through the fender bracket — ensure metal-to-metal contact is clean and tight.
• Moisture inside headlight housing: The rubber dust cap may not be seated properly or could be cracked. Replace the cap and apply a thin bead of silicone sealant around the edge.

Legal Notes

• The H4 halogen headlight must remain DOT-compliant. Aftermarket sealed LED headlights should also be DOT-certified.
• Turn signals must flash between 60-120 flashes per minute per federal regulation.
• Some states require amber front turn signals and red rear turn signals. The 1157NA amber bulbs are compliant in all states for front positions.
• Verify that any aftermarket LED replacement meets FMVSS 108 standards.

Common Mistakes to Avoid

Verification Notes for 2026 Model Year

The 2026 Harley-Davidson Street Bob (M8 117 / FXLSTS) continues the Softail bobber platform with the Milwaukee-Eight 117 V-twin engine. The lighting architecture remains traditional with replaceable halogen and incandescent bulbs. Confirm the following against your owner's manual or a Harley-Davidson dealer:

The Street Bob's use of standard automotive bulb types (H4 and 1157) is one of the advantages of this platform — bulbs are inexpensive, widely available, and easily replaced without special tools or dealer visits. Carry a spare H4 bulb and a spare 1157 bulb on road trips for emergency replacements.

To verify all specifications, check your 2026 Street Bob owner's manual included with the motorcycle, or access it through the Harley-Davidson mobile app.

This guide was prepared using Harley-Davidson OEM specifications and the known lighting architecture of the 2026 Street Bob (M8 117 / FXLSTS) Softail platform. Always verify against your specific owner's manual before performing maintenance.