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12S headlight wiring upgrade

toma nova

toma nova

Cruisin' Guzzisti
GT Contributor
Joined
Oct 4, 2012
Messages
113
Location
Houston, TX
I know that most bikes lose a lot of juice from the battery through wiring to the headlight and I’ve learned that this is even worse with MGs since everything flows through the dash. I took some measurements at the headlight bulb connectors and found the following with the bike running:

Stock
Battery: 14.28V
Tail light: 13.73V
Low Beam: 13.48V
High Beam: 13.75V

Improved
Battery: 14.27V
Low Beam: 14.38V (added almost a full volt from stock)
High Beam: 14.40V (added almost .75 volt from stock)

I added two Panasonic mini relays and some direct wiring from my aftermarket fuse block (which is wired about 3” from battery) – I use http://www.easternbeaver.com for all my electrical parts and accessories – top notch Japanese quality and great service and expertise from an expat Canadian rider, Jim Davis. The two relays and heavier gauge wiring barely fit inside the headlight bucket, but everything goes back together fine. [I also changed the low beam bulb to a Sylvania Silver Star and am playing around with the headlight aiming to get more light down the road.]

Sorry about the crayon drawing, it's the quickest way to get a diagram on paper! (I couldn't get the letter sized .jpg embedded so I attached it instead.)

HTH,
Tom
 
Wow, the voltage drop on the stock wiring is shocking. MG is obviously skimping on the wire gauge.

I am just about to add a headlight modulator (for use on the freeway only when I'm lane splitting) and will look into the upgrade you suggested.
 
Brian UK said:
Your diagram misses out the two relays which are already there.
Click to expand...

I didn't change any of the existing stock wiring, only added 12 ga.(edited) power directly from the battery. If there are stock relays, they're not helping the voltage drop much (see the stock voltage) - the additional relays and thick wiring from the battery (not through the handlebar switch or the dash) brings the voltage back up to full power.

Tom
 
I'll be purchasing an Eastern Beaver kit for my R100GS. Without even bothering to check the voltage at the socket, I'm certain the kit will help. The light on the old GS has always been more yellowish in cast than blue/white. Driving the headlight directly from the battery should be a marked improvement.

Bob
 
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