Voltage Regulator / Rectifier — Honda CB175 / CB200 / CB350 / CB360 / CB450 / CB500T
This modern solid-state combo unit replaces both the factory voltage regulator and separate rectifier on all Honda 12V twins. The factory charging components are the most failure-prone electrical parts on these bikes — upgrading to a single combo unit is the best electrical upgrade you can make.
Why You Need This
The charging systems on the CB175 through CB500T use a single-phase permanent magnet design that is weak by modern standards. The factory voltage regulator and rectifier are separate components that degrade over time, leading to undercharged batteries, dim headlights, and no-start conditions. This combo unit replaces both parts with one solid-state unit — more reliable and easier to install than the originals.
Specifications
| Replaces OEM | 31400-292-670, 31700-455-671, 31700-292-008, 31700-358-305 |
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| Fits Models | CB175 / CL175 / SL175 (1968–1973), CB200 / CL200 (1973–1976), CB250 / CL250, CB350 / CL350 / SL350 (1968–1973), CB360 / CL360 / CJ360 (1974–1977), CJ250T, CB450 / CL450 (1965–1974), CB500T (1975–1976) |
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| Qty | Sold Individually |
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Note: This unit does NOT fit the Honda CB500K, CB550, or CB750 — those use three-phase charging systems requiring a different regulator/rectifier.
What's Included
- Regulator / Rectifier combo unit
- Square plug connector (use as needed)
Model-Specific Notes
- CB450 K0 "Black Bomber": Same setup as later bikes but different wiring colors from the stator coil. The K0 did not have a factory voltage regulator — only a rectifier. Wiring: brown from stator → pink on new unit; yellow and pink from stator combined → yellow on new unit; 12V switched positive → black on new unit.
- CB175 / CL175 / SL175 / CB200 / CL200: The main ground is routed through the stock rectifier, the harness may not reach the new mounting location, and the original rectifier is in a hard-to-find spot. Watch our supplemental CB175/CB200 installation video for these differences.
- Early bikes (pre-1970): Some early models did not have a factory voltage regulator — only a rectifier. This combo unit still works; the black wire provides the voltage regulation that wasn't there before.
Installation
The new unit can be mounted where the old voltage regulator was — typically the bottom of the battery box or near the toolbox. You may need to elongate the mounting holes with a round file to fit the new bolt pattern.
The square plug connector plugs directly into the harness — line up the wire colors (pink, yellow, green, red). If your bike has a round-style connector (common on CB450s), cut off the old plug and solder the included connector leads into the harness. We recommend soldering over crimping for a reliable connection.
The single black wire connects where the old voltage regulator's black wire was — any solid black wire in the harness works (they're all 12V switched positive, controlled by the key switch). The leftover green wire from the old regulator is a redundant ground — leave it alone. The leftover yellow wire is an AC output no longer needed — tape it off and tuck it back into the harness.
For more charging output, do the White / Yellow Wire Stator Coil Mod — a no-tools modification that lets both halves of the stator coil charge the battery at all times.
Frequently Asked Questions
Will this work with my battery?
Yes — this unit works with standard and AGM batteries on all supported models. Typical charging voltages are 12.5–13.2 VDC. We recommend AGM batteries and keeping them on a charger when the bike is stored. This unit is not MOSFET — consult the battery manufacturer if you're considering lithium-ion. See our battery FAQ for details.
Will this fit my CB550 or CB750?
No — the CB500K, CB550, and CB750 use a three-phase charging system with a completely different regulator/rectifier. This unit is for 12V Honda twins only.
What do I do with the leftover wires from the old regulator?
The green wire is a redundant ground — leave it alone. The yellow wire is an AC output no longer needed — tape it off and tuck it into the harness.
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Last updated: March 2026
