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US FlagThursday, May 23, 2024

Welcome to the British Motorcycle Wiring Helper


Most Vintage British Motorcycles used wiring harnesses and components from Lucas. Therefore, the WireColors are more or less consistent across brands. The table below covers most WireColors used and attempts to say how they were used. Where there are known differences from the standards, those differences are mentioned in the notes column. You can sort by any of the columns - just click on the header. If you'd like to see how I wire a Norton Commando, look here. I wire Triumphs the same and in fact, my Norton wiring actually mimics my Triumph wiring except that the frame is not ground on a Norton.
Wire Color Stripe Color Color Code Where Used Notes Sample
BlackBGround on Negative Ground MachinesMost machines are positive ground and have no black wires. However, some harnesses (probably after-market) used black instead of red!
On some Triumphs, the horn to ground was Black.
On Triumphs with a horn relay, the relay to horn wire was Black and the horn ground wire was also black.
Black Wire
Black BVoltage Regulator Negative OutputPODtronics, Tri-Spark MOSFET, and most othersBlack Wire
BlackRedBRContact Breaker to Center Cylinder's Coil, TriplesBlack Wire w/Red Stripe
BlackWhiteBWContact Breaker to Timing Side Cylinder's Coil, Twins/TriplesOn singles, this is the Contact Breaker to Coil wire.Black Wire w/White Stripe
BlackYellowBYContact Breaker to Drive Side Cylinder's Coil, Twins/TriplesBlack Wire w/Yellow Stripe
BlueULight Switch (Headlight) to Dip Switch (Handlebar)Some Norton harnesses also use Blue instead of the Blue/Yellow from the headlight switch to the ignition switchBlue Wire
BlueRedURDip Switch (Handlebar) to Dip (Low) BeamBlue Wire w/Red Stripe
BlueWhiteUWDip Switch (Handlebar) to Main (High) BeamBlue Wire w/White Stripe
BlueYellowUYIgnition Switch to Headlight SwitchSome Norton harnesses use Blue for this instead.
On Triumph, to stop confusion I use this from the switched side of the ignition switch to pin 4 of the 3-position headlight switch. Some Triumph diagrams have it as NB and some as NW - in either case that is confusing because they are primarily on the "hot" side of the switch.
Blue Wire w/Yellow Stripe
BrownNStop LightBrown Wire
BrownBlackNBHorn button to horn (See PB Below)Triumph "usually" used this for the horn. Some used PBBrown Wire w/Black Stripe
BrownBlueNUBattery to Ignition Switch if no Ammeter or Battery to Ammeter and see NWBrown Wire w/Blue Stripe
BrownGreenNGTaillight, Pilot Light, Speedo & Tach IlluminationBrown Wire w/Green Stripe
BrownWhiteNWAmmeter to Ignition SwitchI use 14 gauge wire for this and NUBrown Wire w/White Stripe
GreenGDynamo FieldOnly on Magneto machinesGreen Wire
GreenBlackGBStator Low Output (RM19), One Leg (RM24)Green Wire w/Black Stripe
GreenRedGRLefthand Turn SignalGreen Wire w/Red Stripe
GreenWhiteGWRighthand Turn SignalGreen Wire w/White Stripe
GreenYellowGYStator High Output (RM19), One Side (RM21), One Leg (RM24)On Norton, also goes to the Warning Light AssimlatorGreen Wire w/Yellow Stripe
Light GreenBrownLGNTurn Signal (Direction) Switch (Handlebar) common to Flasher UnitLight Green Wire w/Brown Stripe
PurpleBlackPBHorn button to horn (See NB Above)As far as I know, this color was always used on NortonPurple Wire w/Black Stripe
RedRGround on Positive Ground MachinesFor Norton, I use 14ga for the main ground wires. For others, I use 14ga at least for the battery to frame.
Some harnesses replaced this with black, but that is not common.
Red Wire
RedBlackRBLighting Switch to Pilot LightOn later bikes, this was changed to Brown/Green so the pilot light was on whenever the tail light was onRed Wire w/Black Stripe
RedGreenRGOil Pressure Switch to Oil Pressure Indicator (Red)Triumph before KE00001, after see WNRed Wire w/Green Stripe
WhileGreenWGStator Common (RM19 & RM24), One Side (RM21)On Norton MKIII this also goes to the Warning Light AssimulatorWhile Wire w/Green Stripe
WhiteW"Hot" when the igniton is on.Goes to each handlebar console, the brake switches, and if no kill button, the coils. See WYWhite Wire
WhiteBlackWBContact Breaker (Distributor) to Ignition CoilOnly on Magneto machines. Note: The Norton MKIII workshop manual wiring diagram incorrectly shows this instead of Black/White as the timing side contact breaker to coil wire.White Wire w/Black Stripe
WhiteBlueWUUnder tank junction to ballast resistorNorton, See WYWhite Wire w/Blue Stripe
WhiteBrownWNOil Pressure Switch to Oil Pressure Indicator (Red)Triumph from KE00001 onWhite Wire w/Brown Stripe
WhiteBrownWNWarning Light Assimulator to Charging Indicator (Red)This is standard for a Norton but I remove the assimulator and install an oil pressure switch connected to this wire.White Wire w/Brown Stripe
WhitePurpleWPBallast Resistor to Ignition CoilsNortonWhite Wire w/Purple Stripe
WhiteRedWRStarter Switch (Handlebar) to Starter SelenoidNorton MKIII, Triumph T160White Wire w/Red Stripe
WhiteYellowWYEngine Kill (Handlebar)Triumph Twins/Triples when no balast resistor is used: To coils.

Norton Commando, Pre-MKIII: To junction under tank where it connects to the White/Blue which connects to the balast resistor.

Norton Commando MKIII: To the balast resistor.
White Wire w/Yellow Stripe
Yellow YPODtronics single or three phase input from stator Yellow Wire
YellowYDynamo OutputOnly on Magneto machinesYellow Wire
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