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TLOTM Sept. '08
1,629 Posts
In this post this morning by TLDV8 he references a mod by SteveTLS for Headlight Cut Relay, to inhibit the power to the lights while starter is cranking.

This is a vey useful mod - I was surprised the bike didn't already incorporate that - another example of pretty weak engineering by Suzuki on the electrical side of things.
By inhibiting the lights during the starter crank, it allows the battery to sustain a higher voltage, for both cranking but more importantly, the coil primary voltage.
This works really well ideally done in conjunction with the '+' mode.

I was also surprised not to see this mentioned in the frequent mods.
So while not my original concept or design, (acknowledgement SteveTLS), thought it would be appropriate to document the process as I did my own install, for those who may wish to follow.

This is the original schematic & instruction from Steve.

I made a few minor changes in how I planned to incorporate the mod; electrically however, it is identical.
This more or less came down to convenience/accessability for the physical modification.

As you can see from the new schematic I simply relocated the connections to the other side of the interface connector for the Right Bar Switch.

Start by unplugging both the left & right switchgear harness connectors from the main headlight/instrument wiring harness.

The initial part of the mod will take place on the harness of the right switchgear.
The Yellow/White of the main harness actually connects to an Orange/Red wire in the switchgear harness which loops back to the Black/Red wire in the main harness.
The Yellow/Green of the main harness continues as Yellow/Green in the Switchgear harness

Find the Orange/Red loop & cut it at its midpoint
Find the Yellow/Green wire & cut it about 3" from the connector.

Prepare extender wires to attach to these cut ends.
I used two red wires, one each for each of the orange/red wires (it is not a problem if these two are the same colour)
Use a different colour - yellow in my case - to attach to the yellow/green wires
- the two cut ends of the yellow green will re-attach to the new yellow wire. (actually shown as green in my schematic) :coocoo
Install a piece of heatshrink over the long yellow/green end, before soldering the joint!

Shrink the heatshrink over the joints to insulate (or tape, but h/shrink is neater)

Note that if you are not comfortable soldering you can always use barrel crimps.

Fold the three wires against the harness & secure the end with some tape.

Connect spade terminals to the other ends of the wires and connect to the relay.
The reds go to 30 & 87a (it does not matter which is which) and the yellow to pin 85.
Also connect a length of black wire with a spade to termina 86 and run this back down along with the other three wires.

Fix the relay to a convenient location with adhesive velcro tabs.

Now go to the LEFT switchgear plug & locate the black/white wire.
Connect the free end of the black that originated at the relay pin 86 to this wire, similarly to previous for right side.
Cut the black wire mid-point & install male/female butt connector to each end (this makes removal easier down the road if necessary)

Plug everything back together & test. When you turn on ignition, the headlights should be on. When you crank the starter, the lights should go out completely (not just dim or flicker)

Tidy up the harnesses & tie off appropriately ensuring they are free as bars turn to extremes.

edit: Edit: please ensure the relay is securely mounted in a location that cannot interfere with the steering in the event it should become detached from the velcro. An alternative consideration for fastening, which I have since employed myself, is to use 3M double-sided Urethane tape instead of the velcro. Much more secure fixture. I figure the 'mechanics' of the mod are more up to the individual on how it is installed - just think safe!
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