twin headlights on a '79 GS1000 ?

[Anonymous]

Wondering if the generator on my '79 GS1000 should keep pace with TWO 60/55 watt headlights switched on all the time? Fitted an aftermarket Kawa GPZ-style nose fairing recently with twin 5.75'' Cibies. Comes with it's own sub-loom with one relay for both low beams and one for both high beams (to prevent the switch and wiring from burning out). Has it's own dedicated power feed from the battery positive but uses a common earth.

Have been informed that GS1000 250 watt generator is easily capable of handling the extra load, but I'm only getting around 12.2 volts (idle) to 13.5 volts (5,000 rpm) with the lights on. The battery is gradually draining down and needs regular boost charges. Charges perfect 14.4 volts with the lights off.

Bike has new Electrex stator, reg/rectifier and Yuasa battery.

Thanks all.

[DJones]

The GS Charging systems are very fragile. Get rid of the two 60/55 watt bulbs and use two 35 watt bulbs.

[saaz]

If everything is in good shape it could handle the load. I used to run a single 130/90 bulb all the time. My stator now is a bit older and would be pushed a bit. I also have modified the wiring to use relays instead of power going through the ignition switch and headlight on/off switch - these mods provde an increase in efficiency.

Use a voltmeter in the fairing to keep an eye on things.

[saaz]

Forgot to mention that running the 130 and using handlebar warmers was a bit beyond the charging system for extended periods on the highway

[Anonymous]

Thanks folks, your opinions confirm what I've been thinking. I guess the generators on these old bikes are adequate for stock accessories, but nothing much more. Should've bought the single headlight fairing, I suppose!!

[Guy]

Nonsense. The charging system will cope all right. The use of relays, heavier wiring and good clean connections in the lighting system are essential though. (Lower resistance = higher voltage) There are plenty of previous posts on this subject for reference.

[Anonymous]

That was my original impression. Guess I should continuity-check the entire wiring loom, see if that gets me anywhere.

Maybe a complete re-wire would be a good idea, considering how old this thing is.

Guessing several people out there have re-wired these bikes. If so, how much difference did it make?

[DJones]

Rewiring would only prevent you from burning and melting the wires.( I am assuming that you would use heavier gauge wire of course) The charging system still would not be able to supply no more than 250 watts of power. Increasing the amount of accessories could result in inadequate battery charging, dim lights, or ignition problems. If you want to use a dual headlight system, You should get two 35 watt halogen bulbs.

[Billy Ricks]

I guess I'm lucky to have one of the last GS models produced. The last in the 700/750 class for the U.S. The 1150 was sold for one more year in the U.S. and the 500 went on up until the last couple of years. My bike was equipped with a 310 watt alternator. No problem running 100 watt and higher high beams.

[KEITH KRAUSE]

Nonsense. The charging system will cope all right. The use of relays, heavier wiring and good clean connections in the lighting system are essential though. (Lower resistance = higher voltage) There are plenty of previous posts on this subject for reference.

Good clean connections and larger wire size will lower resistance.
But lower resistance = higher current/amperage, not higher voltage.
You cannot increase voltage by modifying the wiring harness with larger wire.

[Anonymous]

Nonsense. The charging system will cope all right. The use of relays, heavier wiring and good clean connections in the lighting system are essential though. (Lower resistance = higher voltage) There are plenty of previous posts on this subject for reference.

Good clean connections and larger wire size will lower resistance.
But lower resistance = higher current/amperage, not higher voltage.
You cannot increase voltage by modifying the wiring harness with larger wire.

You're wrong Keith, and Guy's right. What you have in a motorcycle electrical system is multiple resistances, each of which causes a voltage drop. If you had a single resistance you'd be right, as the voltage drop across the single resistance would be 12V (all the system voltage). However what you really have is resistor 1 (the wires, connectors etc) and resistor 2 (the device being powered, e.g. a lamp) The drop across R1 will determine the voltage at the supply side of R2.
In theory this drop is negligible, but if connections are bad and wires degraded it can be measureable.
You are right to say that the voltage can't be increased, but it can be maintained and not lost to generating heat in dodgy wires and connections.

I've noticed that Electrex R/R's regulate very tightly to 12V. Both of my ones fitted to GS1000's produce between 13 to 13.8 volts, rather than well over 14V on the original regulator. This is generally a good thing as it gives the battery an easier time, but will obviously reduce the charging rate, which may have an effect depending on the condition of your system, and your riding type.

Simple arithmetic should tell you that a 250W alternator will cope easily with 2 55/60W bulbs, 2 5W tailights, not much for the ignition and occasional application of indicators and brake lights, supported by the battery. If it isn't you have a problem, and if you are generating 50W of heat throughout your wiring due to dodgy connections that could be it.

I have done a complete rewire on one of my GS's, but if all your connections are in good shape this isn't strictly necessary.

[KEITH KRAUSE]

You said I was wrong about the voltage statement, and then you said I am right?
Maybe it's all in how you want to read things. You can say that multiple resistances create a voltage loss, and you can also say that multiple resistances simply creat more resistance.
My statement about lower resistance = higher current, not voltage, is true.
It is Ohm's law. R = V divided by I .

[Anonymous]

You are both correct - you are saying the same thing, but at a different reference point.

Lower resistance does create a higher current. Lower resistance (in this case due to connections) also has the effect of producing a higher voltage at the load. Note that the load is where you want the voltage applied - not drops due to connections.

[Anonymous]

You said I was wrong about the voltage statement, and then you said I am right?

...about 2 different things. Learn to read.

[KEITH KRAUSE]

Thanks for the "learn to read" comment, very cool.