Wiring harnesses for the Moto Guzzi V50 Monza

Main harness for the V50 Monza

I duplicated an original main harness. In construction, I use the same gauge of wire, the same colors and tracers (stripes), the same length and sheathing, the same terminals, etc. All terminals are of the double crimp, strain relief variety.

• Note: Main harnesses comprise the main - or primary - wiring harness. Each motorcycle also uses ancillary sub-harnesses. The individual sub-harnesses are sold separately.

Originally, Moto Guzzi routed the wires to the ignition switch through the Molex connector. I've found this to be troublesome. I prefer to route the wires directly to the ignition switch without going through the dash harness or any connector. Please let me know if you would like this modification.

Tail light ground

Connects the tail light to ground.

Front turn signals (left and right)

Connects the front turn signals to the dash sub-harness. Ground wires connect to the corresponding wires at the headlight plug.

Main harness to alternator and ignition points

Connects the main harness to the alternator. Also connects the main harness to the ignition points.

Main harness to dash

Connects the main harness to the dash to illuminate the guages, indicator lights, ignition switch, front turn signals, and front brake light switch.

Originally, Moto Guzzi routed the wires to the ignition switch through the Molex connector. I've found this to be troublesome. I prefer to route the wires directly to the ignition switch without going through the dash harness or any connector. Please let me know if you would like this modification.

Main harness to tail light

Connects the main harness to the tail light and rear turn signals.

Dash harness to headlight (EURO version with city light)

Connects the dash harness to the headlight. Also provides ground connections for the front turn signals. The EURO version support the city light.

Dash harness to headlight (USA version only)

Connects the dash harness to the headlight. Also provides ground connections for the front turn signals. The USA version does not support a city light.

Battery cable - positive

Connects the positive terminal on the battery to the starter solenoid. Cable is 6 AWG and is 370 mm (~14 ¹⁄₂ inch) in total length. The battery lug accepts a 6 mm fastener; the starter solenoid lug accepts an 8 mm fastener. If you require something different, please let me know.

Includes rubber cover for the terminal located at the starter solenoid (MG# 12703000).

Battery cable - negative

Connects the negative terminal on the battery to the ground point on the frame. Cable is 6 AWG and is 340 mm (~13 ¹⁄₄ inch in) in total length. The battery lug accepts a 6 mm fastener; the grounding lug accepts a 6 mm fastener. If you require something different, please let me know.

Dash ground interconnect

Provides additional ground connections at the dash for left and right turn sinal dash indicator bulbs.

Easy plug in solution for connecting K&S switches on Small block models originally equipped with Molex plugs.

K&S makes a variety of good quality, affordable handlebar switches that are popular replacements for the original switch gear. The K&S 12-0030 is one popular model.

No more need to fiddle with butt connectors, soldering, or heat shrink. Just plug the 9-pin connector into the plug that came with your K&S switch, and the other end into the 12-pin connector on the back of your headlight shell. Made specifically to support the Small block models. If in doubt as to whether it will work with your model, just ask. I am happy to build to suit your Guzzi.

Please note: Some original handlebar switches were grounded through the handlebar. Other original switches were grounded through the Molex 12-pin connector. If needed for your application, a separate ground wire will be provided for use inside the headlight shell. Simply fit it in position 3 of the 12-pin Molex plug inside the headlight shell (position 1 has a red/black wire). Connect the other end with the piggyback terminal to the ground location inside the headlight shell.

When ordering: Please specify specific K&S switch you are using and the total length needed.

Easy plug in solution for connecting aftermarket left-side handlebar switches on Small block models originally equipped with Molex plugs.

Aftermarket switches sometimes use Molex plugs. Generally, the plugs used do not match the Guzzi size or pin configuration. Tomaselli and Domino switches sometimes fall into this category.

No more need to fiddle with butt connectors, soldering, or heat shrink. Just plug the Molex connector into the plug that came with your aftermarket switch, and the other end into the 12-pin connector on the back of your headlight shell. Made specifically to support the Small block models. If in doubt as to whether it will work with your model, just ask. I am happy to build to suit your Guzzi.

Please note: Some original handlebar switches were grounded through the handlebar. Other original switches were grounded through the Molex 12-pin connector. If needed for your application, a separate ground wire will be provided for use inside the headlight shell. Simply fit it in position 3 of the 12-pin Molex plug inside the headlight shell (position 1 has a red/black wire). Connect the other end with the piggyback terminal to the ground location inside the headlight shell.

When ordering: Please specify the aftermarket switch you are using and the total length needed.

Relay and needed wiring to operate the horns using positive current (instead of the original Guzzi handlebar switch that provided the ground for the horns).

The Domino handlebar switch actuates the horns using positive current whereas the original Guzzi switch actuated the horn by providing a ground. This sub-harness adds a new relay and provides the necessary wiring to actuate the horns.

Installation instructions:

1. You *may* need to remove the fuel tank to gain access to the wiring. Please let me know if you do or do not need to remove it to gain access and I will update these instructions accordingly.
2. Disconnect the existing brown and gray/black wires from the horn.
3. Connect the existing gray/black wire that you just disconnected to the new white/red wire.
4. The existing brown wire will no longer be used. Tuck it away such that the terminal will not make contact with anything else.
5. Connect the new black and gray/black wires to the horn.
6. Connect the new black wire with a ring terminal to ground.

Easy plug in solution for connecting aftermarket right-side handlebar switches on Small block models originally equipped with Molex plugs.

Aftermarket switches sometimes use Molex plugs. Generally, the plugs used do not match the Guzzi size or pin configuration. Tomaselli and Domino switches sometimes fall into this category.

No more need to fiddle with butt connectors, soldering, or heat shrink. Just plug the Molex connector into the plug that came with your aftermarket switch, and the other end into the 12-pin connector on the back of your headlight shell. Made specifically to support the Small block models. If in doubt as to whether it will work with your model, just ask. I am happy to build to suit your Guzzi.

Please note: Some original handlebar switches were grounded through the handlebar. Other original switches were grounded through the Molex 4-pin connector. A separate ground wire is provided if needed for your application.

When ordering: Please specify the aftermarket switch you are using and the total length needed.

3 terminal Molex plug and 3 male terminals

Useful for installing on a universal right handlebar switch.

4 terminal Molex plug and 4 male terminals

Useful for installing on a universal right handlebar switch.

12 terminal Molex plug and 12 male terminals

Useful for installing on a universal left handlebar switch.

Wiring for universal left handlebar switches (headlight, parking lights, horn, turn signals)

Works great with the multitude of universal switches available. Butt connectors and heat shrink are included to splice the sub-harness directly to the wires from the switch. Wire connections should be staggered to yield a smaller overall finished diameter. Larger diameter sheathing is provided to aid routing the spliced wires through the sheathing after all of the connections have been made. Wires to the headlight plug are 800 mm in length. Wire to ground is 1000 mm in length. Wires are intentionally left separate from the 12 terminal plug - so that the wires may be more easily spliced and routed through the sheathing or inside the handlebar.

• IMPORTANT NOTE: As with all switches actuating higher amperage components, I consider a relay for the headlight and horns a good idea.

Plug information:

• Position 1: red/black (power in for headlights)
• Position 2: empty
• Position 3: empty
• Position 4: red (power in for parking lights - almost never needed with non-original switches)
• Position 5: green (power out to headlight low beam)
• Position 6: brown (power out to headlight high beam)
• Position 7: yellow (power out to parking lights)
• Position 8: white (power out to left turn signals)
• Position 9: pink (power out to right turn signals)
• Position 10: gray (ground for headlight high beam flash relay - almost never needed with non-original switches)
• Position 11: white/black (ground to horn)
• Position 12: orange (power in for turn signals)
• Ring terminal: black (ground in for horn)

Wiring for universal right handlebar switches (starter button and kill switch)

Works great with the K&S 12-0203 available from an online retailer such as MG Cycle (would also work equally well with many other generic switches). Butt connectors and heat shrink are included to splice the sub-harness directly to the wires from the switch. Wire connections should be staggered to yield a smaller overall finished diameter. Larger diameter sheathing is provided to aid routing the spliced wires through the sheathing after all of the connections have been made. Wires to the headlight plug are 800 mm in length. Wires are intentionally left separate from the 4 terminal plug - so that the wires may be more easily spliced and routed through the sheathing or inside the handlebar.

• IMPORTANT NOTE: As with all switches actuating higher amperage components, I consider a relay for the coils a good idea and a relay for the starter a necessity.

Plug information:

• Position 1: white/black (starter button / ground out to starter relay)
• Position 2: white (kill switch / power out to coils)
• Position 3: white (kill switch / power in for coils)
• Position 4: black (starter button / ground in for starter relay)

Wiring for universal right handlebar switches (starter button and kill switch)

Works great with the K&S 12-0203 available from an online retailer such as MG Cycle (would also work equally well with many other generic switches). Butt connectors and heat shrink are included to splice the sub-harness directly to the wires from the switch. Wire connections should be staggered to yield a smaller overall finished diameter. Larger diameter sheathing is provided to aid routing the spliced wires through the sheathing after all of the connections have been made. Wires to the headlight plug are 800 mm in length. Wire to ground is 1000 mm in length. Wires are intentionally left separate from the 3 terminal plug - so that the wires may be more easily spliced and routed through the sheathing or inside the handlebar.

• IMPORTANT NOTE: As with all switches actuating higher amperage components, I consider a relay for the coils a good idea and a relay for the starter a necessity.

Plug information:

• Position 1: white/black (starter button / ground out to starter relay)
• Position 2: white (kill switch / power out to coils)
• Position 3: white (kill switch / power in for coils)
• Ring terminal: black (starter button / ground in for starter relay)

Replacement wiring for left handlebar switches

Ready for your switch (MG# 17746020 and MG# 17750301 or MG# 18746040 and MG# 18750340).

Wires are 800 mm in length. Upon request, the wires may be left separate from the 12 terminal plug - so that the wires may be more easily routed inside to the handlebar.

• IMPORTANT NOTE: As with all switches actuating higher amperage components, I consider a relay for the horns a good idea and relays for the headlight low and high beam circuits a necessity.

Replacement wiring for the right handlebar switch

Ready for your switch (MG# 17635000 or MG# 18735040).

Wires are 800 mm in length. Upon request, the wires may be left separate from the 3 terminal plug - so that the wires may be more easily routed inside to the handlebar.

• IMPORTANT NOTE: As with all switches actuating higher amperage components, I consider a relay for the coils a good idea and a relay for the starter a necessity.

Rubber boot/cover for small wire terminals.

Intended to cover smaller wires with ring terminals. Sold each.

Rubber boot/cover for battery cables.

Intended to cover the terminal located at the starter solenoid. Not suitable for fitment at battery terminals. Sold each.

O-ring to seal the large, 100 mm speedometer to the dash.

This O-ring seals the speedometer to the dash.

Set of two O-rings to seal the smaller, 80 mm speedometer and tachometer to the dash.

These O-rings seal each gauge to the dash.

4 connection female spade connector

A great way to connect four wires without the need for male spade terminals (Moto Guzzi typically did not use male spade terminals on wiring harnesses). Accepts 6.3 mm (¹⁄₄ inch) terminals. Sold each.

Best to use a needle-nosed pair of pliers to insert and remove terminals.

3 connection female spade connector

A great way to split power to two devices such as driving lights, front and rear turn signals, etc. (Faston or Mamut number 405). Accepts 6.3 mm (¹⁄₄ inch) terminals. Sold each.

Best to use a needle-nosed pair of pliers to insert and remove terminals.

2 connection female spade connector

A great way to connect two wires without the need for male spade terminals (Moto Guzzi typically did not use male spade terminals on wiring harnesses). These are used on the Tonti framed models (Faston or FasBlok) and could be used in custom applications on the loop frame models. Accepts 6.3 mm (¹⁄₄ inch) terminals. Sold each.

2 connection bullet connector

A great way to connect two male bullet terminals (double bullet connector). Accepts 4 mm (0.157 inch) terminals. Sold each.

Single terminal bulb holder

A very nice single terminal bulb holder with excellent fitment within the tube that is secured to the dash. Includes color-coded short jumper wire with a 4 mm female bullet terminal to mate perfectly with the original wiring harness. Accepts standard sized OEM bulbs. ~12 mm OD. Sold each.

When ordering: Please specify wire color and terminal.

Dual terminal bulb holder

A great replacement dual terminal bulb holder and very close to the original in design. Accepts two 6.35 mm female spade terminals, just like the original. Excellent fitment within the tube that is secured to the dash. Accepts standard sized OEM bulbs. ~12 mm OD. Sold each.

Dual terminal bulb holder

A great replacement dual terminal bulb holder and very close to the original in design. Accepts two 6.35 mm female spade terminals, just like the original. Excellent fitment within the tube that is secured to the dash. Accepts standard sized OEM bulbs. ~12 mm OD. Sold each.

Light bulb for gauge and indicator lights

3.36 watt lamp, bayonet base, 500 hour average life, approximately 10 mm (0.41 inch) in diameter. Sold each.

Note: The MG# 93450322 bulbs are longer in overall length, but brighter than MG# 10744910. In general, I recommend MG# 93450322 because they are brighter and easier to see. If you know that your dash requires a shorter bulb, please order MG# 10744910.

This bulb may also be used as a city light or pilot light.

Light bulb for gauge and indicator lights

1.728 watt lamp, bayonet base, 1000 hour average life, approximately 10 mm (0.41 inch) in diameter. Sold each.

Note: The MG# 93450322 bulbs are longer in overall length, but brighter than MG# 10744910. In general, I recommend MG# 93450322 because they are brighter and easier to see. If you know that your dash requires a shorter bulb, please order MG# 10744910.

Light bulb for indicator lights

2 watt lamp, bayonet base, 1000 hour average life, approximately 7 mm (0.28 inch) in diameter. Sold each.

Light bulb for tail light

Long life bulb to help prevent failure due to vibration (1157LL), dual element, 26.88 / 8.26 watt lamp, bayonet base, 2400 / 10000 hour average life. Sold each.

Light bulb for turn signals and parking lights

Long life bulb to help prevent failure due to vibration (1156LL), single element, 26.88 watt lamp, bayonet base, 2400 hour average life. Sold each.

Light bulb for gauge and indicator lights

3.78 watt lamp, wedge base, 2500 hour average life, approximately 10 mm (0.41 inch) in diameter. Sold each.

Light bulb for indicator lights

1.40 watt lamp, wedge base, 500 hour average life, approximately 5 mm (0.23 inch) in diameter. Sold each.

Starter button bracket

Bracket to fit the original starter button (22 mm diameter mounting hole). Stainless steel. Very nice. Starter button sold separately. Sold each.

Starter button

Momentary push button switch to actuate the starter. Fits the original bracket perfectly (22 mm diameter mounting hole) and comes complete with set screw terminals just like the original. Sturdy metal housing and nice quality black plastic securing nut. Sold each.

Starter button

Momentary push button switch to actuate the starter. Fits the original bracket perfectly (22 mm diameter mounting hole) and comes complete with set screw terminals just like the original. Nice quality black plastic housing and securing nut. Sold each.

Original fuse block

New production, very good quality fuse box. Accepts six fuses (MG# 17742550 or MG# 12742500). Comes with clear cover and two jumpers. Additional jumpers available. Sold each.

Jumper for original fuse block

Jumper connection used to join multiple fuse circuits. Fits the original fuse box. Sold each.

25 amp fuse

Original style fuse to fit the original fuse block. Sold each.

16 amp fuse

Original style fuse to fit the original fuse block. Sold each.

Fuse holder

Single fuse holder that may be connected to other single fuse holders to form a row. Sold each. Fuses sold separately.

15 amp ATO / ATC fuse

As used on many modern Guzzis accepting blade style fuses. Sold each.

5 mm post to 6.3 mm male spade adapter

~5 mm diameter hole permits fitment to the neutral switch and dash grounding points (as original). One required per neutral switch. Dash usage varies by model. Sold each.

Bracket for mounting LED turn signal flashers

Designed specifically for LED flashers that are rubber mounted. Mounting hole is 7 mm in diameter. Sold each.

Bracket for mounting turn signal flashers

Fits standard sized round thermal and electronic flashers. Mounting hole is 6 mm in diameter. Sold each.

Push-pull switch

Good quality switch with screw-type terminals. 25 amp capacity. 8 mm × 1 mm threads. Knob unscrews for fitment. Sold each.

Bracket for push-pull switch

This bracket is identical to the starter button bracket, except the hole is ~8 mm in diameter. The intent is to mount this bracket on the left clutch perch, mirroring the starter button bracket. Then, a push-pull switch may be fit to the bracket and used to conveniently actuate spot lights or other electrical components. Stainless steel. Very nice. Push-pull switch sold separately. Sold each.

Toggle switch

Excellent quality SEALED switch with six quick connect terminals (as original). 15 amp capacity, on-on double pole double throw, comes complete with mounting hardware (as shown). Sold each.

Half height toggle switch boot

Half-height boot for the toggle switch. Uses standard ¹⁵⁄₃₂-32 inch threads. Be sure to rotate the toggle with the boot when fitting the boot to the switch. Sold each.

Full height toggle switch boot

Full-height boot for the toggle switch. Uses standard ¹⁵⁄₃₂-32 inch threads. Be sure to rotate the toggle with the boot when fitting the boot to the switch. Sold each.

5 pin mini relay (SPDT) with mounting bracket.

40 amp rating.

Sealed construction. Resistor is used across the coil terminals for long life and reliable service. 40 amp maximum continuous current rating on the normally open circuit. 30 amp maximum continuous current rating on the normally closed circuit.

Great replacement for the starter relay or for use with custom functions. Mounting bracket has a 5.5 mm diameter hole. Sold each.

5 pin mini relay (SPDT) without mounting bracket.

40 amp rating.

Great replacement for the starter relay or for use with custom functions. Sold each.

5 pin mini relay (SPST) without mounting bracket.

Sealed construction. 40 amp maximum continuous current rating.

So far, the only Guzzi I know of that requires this relay is the 1000 S series 2 with the later Digiplex ignition module. As far as I know, all other applications should use MG# 28732560. Sold each.

5 pin micro relay (SPDT) without mounting bracket.

30 amp rating.

Sealed construction. Resistor is used across the coil terminals for long life and reliable service. 30 amp maximum continuous current rating on the normally open circuit. 20 amp maximum continuous current rating on the normally closed circuit.

Used on many later Guzzis. Fits my custom relay solution. Great for use with custom functions. Sold each.