Another question about charging system

[Greg O.]

I have been going through my 1979 GS750 L getting it ready for the next season. Riding season here in Michigan hasn't started yet, at least for me. I decided it would be a good idea to check the connetctions, and grounds. The Bullet connecters look new as this bike has always been garaged, but I think I will replace them anyway.

My question concerns the third leg of the stator that goes through the headlight switch. My understanding is that when the headight is shut off, the system charges on only 2 of the legs. When the lights are on, all legs are charging. Is this type of system doomed to eventually fail? And should I just bite the bullet and replace the old rectifier with the Honda RR? I checked the voltage last fall, I don't remember the exact number, but it was in the high 14s volts with the headlamp on. What about replacing the stator. As far as I know it is original. I just don't want to get let down somewhere, but hate spending money if I don't have to.

Question 2:

Since any power that isn't used is wasted as heat through the rectifier, is it better to run on high beam durring daylight, or does that put an increased load on the stator, in which case it would be better to use low beam. What do you think?

Greg O.

[Steve]

Greg,

My son's 650 had the wire going to the headlight switch as you describe. I was a bit surprised to find that charging output was actually better with the headlight ON, as the output of the third leg of the stator was just a bit more than the headlight demanded.

Nothing wrong with this system, in principle. The biggest drawback is that there are a bunch more connections in that third wire, and that is where any failure might lie. If you tend to run with your headlight ON most of the time, anyway, you would be better off just bypassing that run to the headlight switch and go straight to the R/R. One advantage of this setup is that you can leave the headlight OFF while starting the bike, minimizing the load on the battery until the engine is running and the battery is being recharged.

Should you upgrade to the Honda R/R? If you are still seeing good voltage, no need to do it right now, but go ahead and get one to have it on hand for when the time comes.

Run high- or low-beam? Ideally, you want to run enough load to minimize the dumping of excess that is produced by the stator. A stator-based system is not load-sensitive. It will always put out all that it can, and depends on the regulator to take care of the excess. The high beam does not draw that much more than the low beam, but it might make you more visible to oncoming traffic. An even better option for being seen by oncoming traffic would be the use of a headlight modulator.

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[Greg O.]

Thanks Steve for the reply.

This afternoon I cut all the bullet connecters off and hard soldered the wires. I then checked the voltage, and I also noticed the voltage was higher with the light switch on by about .4 volts. I was wondering about the connections and extra wire going all the way up to the light switch. I like your idea of bypassing it. Just have to remember to turn the lights on. I always run with lights on, except if I forget to turn them on when on rare occasion I might shut them off, i.e. cold weather starting.

Does a light modulater shorten the life of the head lamp? I assume there must be a switch for night operation.

Thanks,

Greg

[Steve]

Does a light modulater shorten the life of the head lamp? I assume there must be a switch for night operation.

I have not seen any scientifically-performed tests, but general concensus is that a modulator will not shorten headlight life, and may, in fact, lengthen it a bit. The lamp is not operating at full voltage all the time, and this is what helps. It has been speculated that a cold filament is more brittle and prone to breakage when hitting bumps, so a warm filament will absorb the bumps better.

If a modulator is made to conform with federal regulations (and most of the are), it will have a photocell in the design that will prevent operation in low-light conditions. Although it is legal to have either the low- or the high-beam modulated, most manufacturers modulate the high beam. In the case of headlamp failure, this leaves your normal low beam for nighttime operation.

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