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Headlight Cut while Startup

6K views 4 replies 4 participants last post by  Noah 
#1 ·
Originally from Decosse at EviltwinSBK.com

DEcosse said:
Most bikes no longer have separate power switches for the headlights, being permanently on with ignition (whether high or low beam)
My Triumph has a good standard feature that removes power from the headlights during the starting operation. The headlights already draw a significant current and when the starter is operated this combined load of starter plus lights will sag the battery voltage considerably, even a well-charged one.
Removing the power from the lights during the cranking operation will mean less voltage sag and that means more voltage to the coils, which will improve starting performance.

Suzukis - and some other bikes - do not have this feature, but is a very simple - and cheap! mod to incorporate.

All you need is a 5-pin automotive relay and some wire.
You need to refer to your own bike/model specific wiring diagram but this can be incorporated on pretty much any bike that does not have this standard feature.
The basic fundamental is to break the power feed leading to the dimmer switch:
(by installing prior to the dimmer switch, the mod will work whether in hi or lo - also will be good regardless of whether the OEM bike uses relays to switch power or direct, as in the Suzukis case)
Connect each side of the break to the relay, pins 30 & 87a - these are the normally closed poles of the relay i.e. when no power applied to the coil, the connection will be made between them
Next find the power feed from output of the starter switch and tap a wire onto that line and connect to pin 85 of the relay
Finally, connect pin 86 to your ground return circuit (black/white on Suzuki)

Mount your relay to convenient spot using Velcro tabs or I prefer double-sided 3M Urethane tape.



Test your mod:
Turn on ignition - headlights should come on as normal.
Thumb the starter button - lights should go out while starter depressed and return when released.
Hint: - Note that it is easier to test if you DON'T pull in the clutch lever - the starter won't spin obviously but you will still see the effect of the mod.

Here's where I actually connected in on the TL - I think the SV circuit is very similar, certainly on the curvey.

 
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