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Motorcycle Regulator Rectifier

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This is the ultimate guide to the humble motorcycle regulator rectifier.

We’ve included a whole host of learning material and educational data, to help get to grips with these apparently simple devices.

Thinking of sourcing a new regulator rectifier?

Start with the basics. Skip out the waffle.

Find out all that you need to know before making your next purchase.

2 phase 4 wire motorcycle regulator rectifier
A photograph of a 2 phase 4 wire motorcycle regulator rectifier

Taking power from the engine and giving it to the battery…

Explanations everyone can understand. Layered into what you actually need to know. Before building on complexity until you’ve had enough and beyond.

We’ve even stripped down the motorcycle regulator rectifier to its basic engineering principles.

Wrapping up each principle into an everyday system that does exactly what a regulator rectifier needs to do… “Taking power from the engine and giving it to the battery.”

Motorcycle Regulator Rectifier Technical Data

Browse below to find detailed, technical data about motorcycle regulator rectifiers. If you think we’re missing something get in touch and we can publish it here for everyone to see.

The Basics

To cover the basics of motorcycle regulator rectifiers, we’ve split this section in three key topics…

  1. Motorcycle regulator rectifiers simplified
  2. Regulator rectifier standard wire colours
  3. Regulator rectifier wiring basics

Motorcycle Regulator Rectifiers Simplified

Most motorcycle regulator rectifiers are plug & play devices. But they are not all the same!

When sourcing a new regulator rectifier there are two essential things to find out first:

  1. The number of wires needed
  2. What each wire does

Regulator Rectifier Standard Wire Colours

Most manufacturers have adopted subtle variations of Honda 1970’s classic motorcycles. Becoming widespread these are now the most commonly used wire colours:

  • Yellow, White or Pink = AC Inputs
    • from the stator to the regulator rectifier
  • Red = V+
    • from the regulator rectifier to the positive battery terminal via a fuse
  • Green = V-
    • from the regulator rectifier to the negative battery terminal
  • Black = Vsense
    • positive feedback voltage from the wiring loom to the regulator rectifier

Regulator Rectifier Wiring Basics

This list shows the basic connections of a regulator rectifier:

AC Inputs

The AC inputs provide the power to the regulator rectifier. And so, each one is an individual AC phase.

Connect these to the stator windings. Orientation is not important in this application.

DC Outputs

The DC outputs provide a regulated voltage for the battery. A positive voltage and a reference voltage wire.

Connect these to the battery. Orientation is very important with DC.

(Optional) Vsense

Vsense is an electronic switch wire. Removing voltage disconnects the battery from the internal circuitry. Therefore, there is no current leakage if the rectifier becomes damaged.

In older voltage regulators, Vsense was used to measure voltage in the wiring loom. The measured voltage was then used as the reference for adjustment.

This did help classic systems reduce the impact of voltage drops under heavier loading. However, modern motorcycles get around the problem with electronics.


Although the principle operation of regulator rectifier devices is the same, there are many different specifications, formats and designs.

As always, the internal electronics and overall build quality of motorcycle regulator rectifiers vary between manufacturers.

Therefore, when sourcing a new regulator rectifier, it’s important to consider evaluating the following before diving straight in:

  1. Output voltage
  2. Power output
  3. AC phase count
  4. Vsense and On/Off Switching
  5. Mechanical dimensions
  6. Connectors
  7. Negative and positive earth wiring

Continue to read the sections below to gain a more detailed understanding…

Output Voltage

The rated output voltage must always match your battery voltage.

Regulator rectifiers are commonly found as either 6 or 12 volts.

Be wary though, as the actual output voltage of regulator rectifiers should always be slightly higher. Check out our technical guide, “how do regulator rectifiers work” to learn why.

Power Output

Measured in watts, this is maximum rated power output.

If you’re buying a new regulator rectifier, remember that the purpose of the regulator rectifier is to charge the battery. Rather than take on the full load of your system.

In most applications, a 110-Watt regulator rectifier is ample for lights and battery charging. Choose a larger wattage for motorcycles with fuel injection or DC ignition systems.

AC Phase Count

Most motorcycle charging systems are either a 2 phase or 3 phases.

For practical purposes, this means that the stator and regulator rectifier have either 2 or 3 AC inputs wires to connect. It is essential to use all the AC outputs from the stator coils.

To keep it simple, the number of AC output wires on the stator must match the number of AC input wires on the regulator rectifier.

For more information on AC phases and where they come from, check out our motorcycle stator coils data library.

Vsense and On/Off Switching

Some motorcycle systems can isolate the regulator rectifier from the battery when it’s not in use.

This complex action is all done by the internal electronics of the regulator rectifier. All we must do is connect an additional wire during installation.

In most cases, a voltage equal to the DC output is required to turn on the unit.

Mechanical dimensions

Getting the dimensions right when buying a new regulator rectifier will save you whole lot of headache when it comes to installation.

Consider these two things:

  1. The space that is available
  2. The bolt hole dimensions
    • The gap between each bolt hole (if there’s more than one)
    • The diameter of each bolt hole

It’s also wise to check the length of cable that’s available on your loom. Just to make sure that it will reach.


Unless you plan on crafting your own electrical connections this can make sourcing a replacement rather problematic.

Connector Care Top Tips

Most motorcycle connectors have replaceable terminal pins. This means that the pins can be relocated in the connector housing.

So, there’s no need to worry don’t worry about wire positioning in connectors. This can be remedied easily with a sewing needle at home…

  1. Lightly bend down the latch on the terminal pin to remove it from its connector housing.
  2. Then, make sure that the latch is still in good condition, before finally clicking it into the location you need.

Negative and positive earth wiring

For most motorcycles this section can be overlooked.

The bulk of motorcycles on the market are negative earth. And regulator rectifier manufacturers have accommodated this trend nicely.

Any Regulator Rectifier?

For those classic renovators among us that love positive earth set ups…

Yes, you can use any regulator rectifiers that meets your needs. Providing that its internal circuitry is isolated from any external metal casings.

In every application, always connect a regulator rectifiers DC outputs as per the battery. Positive to positive. And negative to negative. Always, every time.


Here are a few things to extra points to consider regarding the cross compatibility of motorcycle regulator rectifiers:

  1. Voltage
  2. Old system conversions
  3. Modern bike electronics


Regulators with a different voltage rating are not cross compatible.

12-volt regulator rectifiers must only be used with 12V systems.

And so, 6-volt units must only be used in 6-volt systems.

Using a 6-volt regulator rectifier in a 12V system will cause it to over overheat and fail. This is because the connected 12-volt electrics will pull more current from the regulator rectifier to compensate for the reduced voltage.

While using a 12-volt regulator rectifier in a 6-volt system will cause irreparable damage to the connect 6-volt system. This is due to the higher voltage being fed into the 6-volt system.

Old System Conversions

It is possible, and even recommended, to swap out old rectifier and condenser systems, for a modern combined regulator rectifier unit.

One reason is the improved smoothness of the DC output.

Although for bike builders the main reason to convert an old system is for simplicity.

All in one, combined regulator rectifiers are more widely available than the older condenser systems. They also require less wiring, and diagnostics and replacement are far more straightforward.

The internal electronics are also better at regulating a smoother DC ripple. Even during changes in electrical load.

This results in better quality battery charging and ultimately improved battery life span.

Modern bike electronics

It’s important to note the big electrical loads on a bike before souring a replacement regulator rectifier. With fuel injection systems, ABS controls and ECU’s a regulator rectifier with a higher power output will be essential.

Our best advice is to research the power output of your current regulator rectifier.

Then source a replacement regulator rectifier with a similar power output, but never a lower power output.

Using a lower power regulator rectifier will increase system wear and tear.

You can always use a regulator rectifier with a higher output. In fact, this is often recommended as this can reduce wear and tear.

However excessive amounts of spare power can mean that the regulator circuitry is not running at optimum efficiency which can impact on battery life.

FREE Regulator Rectifier Wiring Diagrams

Huge buttons to navigate to Lamberts Bikes motorcycle regulator rectifier wiring diagrams. Download them direct to your device or view them online!

We’ve categorized all our regulator rectifier wiring diagrams into 2 phase and 3 phase systems. For more information on what ‘phase’ means, check out our regulator rectifier technical guide “how do regulator rectifiers work”.

2 Phase Regulator Rectifier Wiring Diagram Links

4 pin

4 wire

5 wire

4 Pin Regulator Rectifier Wiring Diagram

4 Wire Regulator Rectifier Wiring Diagram

5 Wire Regulator Rectifier Wiring Diagram

3 Phase Regulator Rectifier Wiring Diagram Links

5 wire

6 wire

5 Wire Regulator Rectifier Wiring Diagram

6 Wire Regulator Rectifier Wiring Diagram

Learn more…

To learn even more about your motorbikes power circuit, view “how do regulator rectifiers work?”

Properly testing a motorcycle regulator rectifier requires some technical thinking. Understanding some of the results requires an understanding of some basic engineering principles.

That’s why we’ve created an entire webpage, devoted to giving you the low down on regulator rectifier testing. Click here to find out more.

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  1. Doug Broughton

    Hi I have a Bultaco 250 matrella GTS ,motoplat 6v ac 5w/25w/35w , (5w circut tail light,blinkers,horn +6v ac to bat )(6v ac 25w brake light , shows resister I have no value of resister) 6v ac 35w headlight. this is what I have , Can you wire in a Simson motorcycle voltage regulator that has the same value as Motoplat charging system of 6v ac 5w/25w/35w so all three ac circuit to be regulated and produce dcv to charge battery, the 5w ac goes to battery no fuse no rectifier no regulator the 25w brake light with resister in circuit ? not a rectifier ? to ground I thought this would be your charging circuit Help

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