6V Turn Signal and Tail Light Bulbs (SAE 1156 + SAE 1157) | Honda CT90 / Trail 90 / CB100 / CB125
Burnt-out turn signals and dim tail lights are a safety hazard waiting to happen. These 6V incandescent replacement bulbs are direct plug-and-play replacements for the bayonet-style sockets on Honda's vintage 6V lineup — the CT90 / Trail 90, CB100 / CL100, and CB125 / CL125. Sold individually. Pick single filament for turn signals, dual filament for tail/brake lights.
Why You Need This
After 50+ years on a 6V Honda, original turn signal and tail light bulbs corrode, dim, or simply burn out. Many states mandate working turn signals for road inspections — and "I'll use arm signals" isn't going to fly at the inspection station. Fresh 6V bulbs restore full brightness on your stock thermal flasher relay with no wiring changes.
On the tail light, the dual filament does double duty: the dimmer filament stays on as the running light, and the brighter filament fires when you grab the brake. One bulb, two jobs. The single filament style is for the turn signal corners only — one filament fires when the indicator clicks.
Specifications
| Spec | Detail |
|---|
| Replaces OEM Parts | 34905-358-003, 34905-053-000, 34905-056-671, 34906-329-671 |
| Bulb Types | #3251 Single Filament (SAE 1156) and #3252 Dual Filament (SAE 1157) |
| Voltage | 6V |
| Base Type | Bayonet (BA15s single contact / BA15d dual contact) |
| Sold As | Individual bulbs — order the quantity you need |
| Fits Models | CT90 / Trail 90 (K0–K9, 1966–1978), CB100 (K0–K2, 1970–1975), CL100 (K0–K3, 1970–1973), CB125 (S0–SA, 1973–1978), CL125 (S0–S1, 1973–1975) |
Note: Bulbs are sold individually. Order the quantity you need — typically a mix of single and dual filament for a complete set, plus a spare or two for the tool bag.
Which Bulb Goes Where
- #3251 Single Filament (SAE 1156): Front and rear turn signals. Single filament fires only when the indicator switch clicks.
- #3252 Dual Filament (SAE 1157): Tail light / brake light on every bike listed. The dual filament has two elements — a dim filament for the running light and a bright filament for the brake light. The keyed bayonet base only inserts one direction.
Model-Specific Notes
CT90 K0–K2 (1966–1971): The earliest Trail 90s did not ship with factory turn signals from Honda — the turn signal switch was added on K3 and up. Those earlier bikes still need the dual filament bulb for the tail light. If you've retrofitted turn signal housings to a K0–K2, add single filament bulbs for those.
12V Hondas: This 6V bulb does NOT fit 12V Honda twins or inline fours (CB175, CB200, CB350, CB360, CB450, CB500, CB550, CB750). Those bikes need our 12V Turn Signal & Tail Light Bulbs — covers both single and dual filament for the 12V lineup.
Installation
Difficulty: Beginner
- Pop the turn signal or tail light lens off the housing.
- Press the old bulb in slightly and twist counterclockwise to release it from the bayonet socket.
- Apply a dab of dielectric grease to the metal base and sides of the new bulb — prevents corrosion and keeps the bulb from rusting into the socket.
- Press the new bulb gently into the socket and twist clockwise to lock. The dual filament bulb's keyed base only fits one direction — if it doesn't turn, rotate 180° and try again.
- Test the turn signals or brake light before reassembling the lens.
Corroded socket? Work the old bulb loose gently if it sticks — rocking it slightly while pressing in often breaks the seal. Clean the socket contacts before installing the new bulb.
Frequently Asked Questions
What's the difference between single and dual filament?
The single filament (SAE 1156) has one element and serves as a turn signal only. The dual filament (SAE 1157) has two elements — a dim filament for the running light and a bright filament for the brake light. All Honda 6V tail lights from this era use the dual filament. The turn signal corners use single filament.
How many bulbs should I order?
Depends on your bike. A CT90 K3 through K9, CB100, CL100, CB125, or CL125 with factory turn signals takes a single-filament bulb at each turn signal corner and a dual-filament bulb in the tail light. A CT90 K0–K2 without factory turn signals only needs the dual-filament tail light bulb. Order spares for the tool bag either way.
Can I upgrade these 6V Hondas to LED?
The vintage 6V Honda lineup has very limited LED options — most aftermarket LED turn signal bulbs are 12V only, and 12V LEDs will not work on a 6V system. For these bikes we recommend sticking with the incandescent bulbs above. A full 6V-to-12V electrical conversion is possible but is a substantially bigger project than a bulb swap.
Will this fit my 12V Honda (CB175, CB350, CB450, etc.)?
No. These are 6V bulbs and will burn out almost immediately on a 12V system. The CB175, CB200, CB350, CB360, CB450, CB500, CB550, and CB750 all run 12V — see our 12V Turn Signal & Tail Light Bulbs.
My turn signals flash too fast (hyperflash) — is it the bulbs?
Usually, yes. A fast flash typically means one or more bulbs are burnt out — the thermal flasher relay senses lower current draw and speeds up. Replace all burnt-out bulbs first. If the flash rate is still wrong, check our 6V Flasher Relay for these same bikes or look for corroded ground connections.
Why is one filament dimmer than the other?
That's by design on the dual filament tail light bulb. The dim filament is your running light — on whenever the headlight is on. The bright filament fires when you apply the brake.
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Last updated: May 2026
