Round Plug Ignition Key Switch | Honda CB175 / CB350 / CB450 / CB750
A fouled or seized ignition switch is one of the most frustrating no-start problems on a vintage Honda — intermittent, hard to diagnose, and stranding you in a parking lot. This 4-wire round-plug switch is a direct replacement for the OEM unit on Honda's late-1960s and early-1970s twins and fours. Brown housing, leads attached, includes 2 keys.
Why You Need This
Honda ignition switches become fouled and corroded over 50+ years on the road. The tumbler seizes, the contacts oxidize, and the switch starts shorting out or working only when the key is held at exactly the right angle. The fix is a fresh switch and a clean harness plug.
This is the round-plug switch — the 4-wire connector style Honda used on the CB175 K3-K6, CB350 / CL350 / SL350, CB450 / CL450 (K1 and later), and the earliest CB750 K0-K2. The later 360-series twins, CB200, CB350F four-cylinder, CB500K, CB550, and CB750 K3+ use a different switch with a square-plug connector — see the Square Plug Ignition Switch for those.
Specifications
| Spec | Detail |
|---|
| Replaces OEM | 35010-315-017, 35010-315-007, 35010-336-611, 35010-303-003 |
| Connector Style | 4-wire round plug, brown housing |
| Wire Colors | Black (12V to bike harness), Red (battery feed), Brown (taillight), Brown/White (instruments + headlight) |
| Fits Models | CB175 / CL175 K3–K6 (1969–1972), CB350 / CL350 K0–K5 (1968–1973), SL350 K0–K2 (1969–1973), CB450 / CL450 K1–K7 (1968–1974), CB750 K0–K2 (1969–1971) |
| Sold As | Sold Individually — includes 2 keys, leads attached |
Important Notes
Does NOT fit CB450 K0 / CL450 K0 (1965–1967 "Black Bomber" era). Those bikes use a different switch with a 6-wire rectangular connector (Honda OEM 35010-283-000). That OEM is NOS-only — we do not currently carry a replacement.
Does NOT fit the 360-series twins, CB200/CL200, CB350F four-cylinder, CB500T, CB550, or CB750 K3 onwards. Those models use a different switch family — see the cross-links below.
About the photo: The secondary product image shows aftermarket-style keys, but the keys we actually include with this switch are closer in shape to the original Honda-style keys. The photo is a known mismatch and is on our list to update.
About the connector fit: The plastic housing on this aftermarket switch can run slightly looser than the original Honda housing — if your harness female connector has any wear from 50+ years of use, the join may feel loose at first. A small bead of epoxy on the plastic housing seam (not on the electrical pins) firms it up if needed.
Installation
Difficulty: Beginner
Install tip: Before plugging in the new switch, clean the female harness connector terminals with rubbing alcohol and fine steel wool. Decades of oxidation on the female terminals is the most common cause of a loose-feeling connection or intermittent contact.
Wiring color reference: The four wires from this switch are Black (12V out to bike harness), Red (battery feed in), Brown (taillight power-out), and Brown/White (instrument cluster + headlight power-out). If your harness has been re-wired by a previous owner and you're matching colors, see our Ignition System Wiring Design & Diagnostic KB article for the full circuit walkthrough.
Frequently Asked Questions
Will this fit my 1965, 1966, or 1967 CB450 (Black Bomber)?
No. The CB450 K0 and CL450 K0 (1965–1967 "Black Bomber" generation) use a 6-wire rectangular connector that's electrically different from the 4-wire round plug on this switch. Honda OEM 35010-283-000 is the original part number for the K0 switch — it's NOS only and we don't carry a replacement.
How many wires does this switch have, and what are the colors?
Four wires on a round brown connector: Black (12V out to bike harness), Red (battery feed), Brown (taillight), Brown/White (instruments + headlight). The leads come pre-attached.
Will this fit my 360-series (CB360, CL360, CJ360), CB200, or CB350F four-cylinder?
No. Those bikes use the square-plug switch — see our Square Plug Ignition Switch.
Will this fit my CB750?
Only the early CB750 K0, K1, and K2 (1969–1971). The CB750 K3 (1972) and all later CB750 variants use a different switch family — see our Square Plug Ignition Switch for K3–K6 / KA, or the Late Style Ignition Switch for CB550F / CB750F / CB750A and the late K8-K9 era.
Does this come with keys?
Yes — 2 keys are included. The keys are closer in shape to the original Honda-style keys than the aftermarket keys shown in the secondary product photo (the photo is on our list to update).
My old switch had keys cut to a specific code — can I get matching keys?
No — this is a generic aftermarket replacement with its own keys. If you want to keep the original key code, take both the old and new switches to a locksmith and have the new lock cylinder re-pinned, or have the new keys cut to match the original.
The connector feels loose on my harness plug. Is this normal?
It can be. The plastic housing tolerance on this aftermarket switch runs slightly looser than the original Honda housing. If your harness female connector has wear from 50+ years of riding, the join can feel loose. A small bead of epoxy on the plastic housing seam (not on the electrical pins) firms it up if needed. Clean the female harness terminals with rubbing alcohol and fine steel wool first — oxidation on the female pins is the more common cause of a loose-feeling join.
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Last updated: May 2026
