Upgrade to Heavy Duty Wiring for the Headlight

by Allen#212

For those of you wanting more brightness out of your stock bulb and/or using High powered ones, which overheats your stock wiring and switches further reducing the light output, in other words you get more light output out of your stock bulb with this mod and super light if you already run HO bulb. Cheaper than buying+replacing HP bulbs at $50ea IMO. Some copied info.

The wiring is deficient for several reasons,

small gauge wire
too much of it
too many switches
The brightness of a bulb is determined by how much power you can pump through it. The amount of power is determined by the voltage across it. The voltage across the bulb is determined by the source voltage and the resistance of all the wires and switches between the source and the bulb.
The power has to go from the battery, through the main fuse, through the ignition switch, through the main fuse box, through the right hand side starter switch (the headlight turns off when you press the starter) across to the left side high/low beam switch, and then finally to the headlight. All of the wiring is pretty small gauge, (18 I think) and each of the switches adds resistance.

When I did my measurements I measured 9.6 volts across the headlight with the headlight on, but not the engine, as compared to 12.8 volts at the battery. When I hooked the bulb directly to the battery using big wire the voltage was 11.9 volts.

That 2.3 volts makes a significant difference in the amount of light put out by the bulb, as the relationship between power and brightness is not linear, a properly powered 100 watt bulb puts out noticeably more light than two 50 watt bulbs.

Ok you will need,2 relays, apro. 15ft ea. of 16/18+14 gauge wire, assorted wire conn., splices, zip ties, etc,.

I will try to attach diagram or check http://www.mahonkin.com/~milktree/h...ht-harness.gif.

Relay connections not shown on dia. H Beam, #30=to bulb HB terminal, #85 from stock HB wire. L Beam, #30 to bulb LB terminal, #85 from stock LB wire. The heavy green wire from headlight to battery not really needed, just run a length of 14 wire to a good ground anywhere on frame.

I'll be doing this mod soon, will post results+pics.


High Beam Relay
#87 power from batt(+12V)/thick wire, #86 ground/thin wire, #85 Red/Black from stock wiring, #30 to Headlight H.beam/thick wire.

Low Beam Relay
#87(same), #86(same), #85 Red/Yellow from stock wiring, #30 to Headlight L.Beam/thick wire.

Mod Completed

Took me aprox. 3hrs, mostly figuring where to locate relays, inst./attached relays to fairing bracket next to gauges with a zip ties (one on each side), removed stock wires from light plug+ soldered 3ea. new 16 gauge/aprox 8in long wires to each blade connector (you have to remove the blade connectors, easily done by pushing spring tab and pushing out) and make sure to mark/ID connector and/or end of new wires for proper hookup, The stock wires are R/Y=L/Beam, R/B=H/beam, B/Y= ground.
Ran single 12 gauge wire from battery(+) with inline 15 amp fuse to 1st relay H/Beam and spliced a section to 2nd relay L/Beam.
Spliced/ added aprox. 8in. of 18 gauge from stock harness to reach ground+actuate relays, all the ground wires were attached to headlight adj. bracket bolt including the stock B/Y from the stock harness to insure good ground. Used insulated blade connectors at relays and all splices were sealed with shrink tubing to protect from weather.
The voltage at headlight connector increased from 10.2V to 11.8V and the headlight is much brighter.

Anyone with some wiring know how could do this fairly easy, the most important (hardest) thing is routing the wire from the battery(+) to the fairing area, I used "Black" wire for this run and secure to stock harness as much as possible with zip ties, especially around the steering area.

I use the right allen bolt connection at starter relay for power source and placed fuse as close as possible to it, all your grounds are common, I used the headlight adjuster bracket bolt for all my grounds and ran a section of heavy wire from there to the bolt holding the thermostat bracket to frame to insure good ground.

BTY the drawing is simply a schematic for this mod, the wiring color is only for clarity, in actuality on our bikes, the wires from the stock headlight wiring will be used as follows:

1. Red/Black on high beam relay to power (+close) relay at terminal #85(86)

2. Red/Yellow on low beam relay to power (+close) relay at terminal #85(86)

3. Black/Yellow(- ground) can be used to provide ground for both relays at #86(85) or can use frame ground.

Note: you can power or ground the relay thru either #85 or #86, but both connections must be the same!. ie., power 85/85, ground 86. or power 86/86, ground 85. Check this link for info on this relay (very cool) http://www.rattlebars.com/mtz/hornrelay.html

Auto Relay 30 Amp, Radio shack # 275-226

Mod pic L/H side

R/H side

Starter relay, Here's where I got power for headlight mod (and other acc), this terminal is always "HOT" and powered directly from battery, no fuse, so be careful when working/connecting to it, better yet disconnect a batt. lead JIC