Regulator Rectifier for Honda CB 400, CM 400 & 450, CMX 250 Rebel 1978-2016
Regulator Rectifier for Honda CB 400, CM 400 & 450, CMX 250 Rebel 1978-2016
SKU:RM30003
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Regulator Rectifier for Honda
CB 400, CM 400 and CM 450, CMX 250 Rebel, GB 500 - 1978-2016
This is a brand new voltage regulator rectifier supplied as a direct replacement for the original unit. It performs two jobs at once: the rectifier section converts the alternating current produced by the stator into the direct current the battery and electrical system need, and the regulator section holds that output at a safe level so the battery is charged properly without being cooked. Installation is plug and play with no assembly required, and the unit is a direct fit using the factory mounting points.
The body measures 80 mm long by 78 mm wide by 30 mm high, with 65 mm centre to centre between the fixation holes and 260 mm of wire. It carries two plugs, five pins and five wires. The quality exceeds the OEM equipment, with an improved heat sink, better charging capability and a higher grade of electric components than the original. An opposite connector for the main harness side is supplied with the part, because the harness side connector on machines of this age is very often melted or corroded and is itself a common cause of repeat charging faults. Part reference RM30003.
Key Features
- Brand new, direct replacement for the original unit
- Plug and play, direct fit, no assembly required
- Improved heat sink and charging capabilities
- Higher grade of electric components
- Quality exceeds the OEM equipment
- Opposite connector for the main harness side included
Technical Specs
| Specification | Detail |
|---|---|
| Width | 78 mm |
| Length | 80 mm |
| Height | 30 mm |
| Wires length | 260 mm |
| Distance between fixation holes | 65 mm (centre to centre) |
| Number of plugs | 2 |
| Number of pins | 5 |
| Number of wires | 5 |
| Minimum charging voltage | 14.5 V +/- 0.5 V |
| Maximum charging current | 35 A / 400 W |
| Open circuit voltage | Under 15 V |
| Operation temperature | -20 C to 85 C |
Vehicle Fitment Guide
Years shown are the overall coverage span for this part. Please confirm against the OEM part number on your original unit before ordering.
| Make & Model | Years |
|---|---|
| Honda CB 400 | 1978-2016 |
| Honda CM 400 | 1978-2016 |
| Honda CM 450 | 1978-2016 |
| Honda CMX 250 Rebel | 1978-2016 |
| Honda GB 500 | 1978-2016 |
OEM Part Number Cross Reference
Aftermarket replacement. OEM part numbers are listed for reference only.
| Part Number | Manufacturer / Brand |
|---|---|
| 31600-KEN-A51 | Honda |
| 31600-413-008 | Honda |
| 31600-KV8-681 | Honda |
| 31600-KR3-670 | Honda |
| 31600-KR3-671 | Honda |
| 31600-KR3-690 | Honda |
| 31600-KN8-730 | Honda |
Frequently Asked Questions
Will this fit without modification?
Yes. It is plug and play and a direct fit to the original mounting, with two plugs, five pins and five wires matching the factory arrangement. No assembly and no cutting or splicing is required. Confirm the OEM number on your existing unit against the cross reference table before ordering.
What is included?
The regulator rectifier itself, plus the opposite connector for the main harness side so you can renew both halves of the connection at the same time.
How do I know my old regulator rectifier has failed?
Measure the voltage across the battery terminals with the engine running. A healthy system should show around 14.5 V. A reading that stays at or below battery voltage means the unit is not charging, while a reading above 15 V means it is not regulating and is overcharging, which boils the battery and blows bulbs. Repeatedly flat batteries, dimming lights at speed and a scorched or discoloured regulator body are all typical signs.
Why is the harness connector supplied as well?
The regulator connector carries the full charging current and, on machines of this age, the harness side is often melted, corroded or high resistance. A damaged connector will destroy a new regulator, so renewing both sides at once is the reliable repair.
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