Electrical question- RPM determines headlight brightness?

[Lucien Harpress]

First of all, a big thank you to EVERYONE here who's answered questions I've posted previously. Thanks to you, I was FINALLY able to get the bike on the road after three months of working on it. There's still a thing or two to work out, but I'd say she's functioning at about 85% capacity.

One of the minor things I'd like to take a look at is the electronics, namely the headlight and blinkers. When I ride at night (a grand total of two times, mind you), the brightness of the headlight seems to be determined by how fast the engine is running- ie, when I'm cruising along @ 60 mph the headlight is fine, but when I slow down and stop at an intersection, the light dims quite a bit.

Same with the blinkers- they work (blink) when I turn them on. When I stop, so do the blinkers. They remain on, but don't blink. I'm guessing that enough current isn't being drawn to activate the "blink" mechanism.

I haven't taken a meter to any of the wiring yet, mostly because I don't know where to start. I still have to clean a few of the connections in one blinker, but I don't know if the blinkers are tied together in any way- if one isn't drawing enough current, it causes all four to stop? This also doesn't explain the headlight issue. Unless this is somewhat normal for the bike? (I've read of the electrical issues this bike has, and how much current it draws.)

This problem isn't bike-breaking. More annoying than anything. I figured I'd just throw this out and see what I get.

[XJOK2PLAY]

Hi Lucien...

What you're describing sounds like "standard operating procedure" (SOP) for the standards.
There's been several recent threads discussing charging system differences, and their outputs.

T.C. recently posted that the output difference between an XS and an XJ was the XS puts out 20 amps, the XJ, 26 amps.

One of the members has recently posted that he successfully swapped an XS stator w/ an XJ's...

Geezer sells "hopped up" Reg / Rec's. Helps a lot, I hear.

None of these 'ole bikes put out what I would call "stellar" amounts of voltage... and even the XJ's headlights and blinkers will do at times what you describe. One difference is the type of flasher they use. Heat type, instead of electronic... (it has to heat up to break the circuit, then closes when it cools...) Some have swapped out to electronic flashers... ($2-$3, get 'em anywhere.) Our NOS flashers... $45 last I heard! BUT... if you opt for the new cheaper way... they don't have the 3rd wire that is for the auto-cancellor.
So you lose that feature.

Sounds to me like you may be closer to the 100% mark after all !!!
Ride Safe.
Regards,
Bob

[TopCatGr58]

The resident electrical gurus are not on right now, Randy, 3Phase, Geezer. But most of the folks that provide info here can easily tell you that the XS's charging system is weak, and a varying brightness headlight that increases with engine rpms is relatively normal.

HOWEVER, there's a lot you can do to help reduce the overall RESISTANCE on the lines which lets more juice get where it's supposed to, by unplugging EVERY electrical connector, inspecting for corrosion, and cleaning and then applying dielectric grease to keep out additional future corrosion. There are several ground straps, not just the one on the negative end of the battery cable...there's one behind the starter motor to the frame. Also, if you still are using the GLASS fuses, doing the solid ATCO fuseblock upgrade will also help. There are several large connectors BEHIND the fuseblock that come from the ALT, and with corrosion/resistance they can heat up enough to MELT the housings! Also, there are many ground wires where the REG/RECT bolts to the frame under the gastank, removing them, cleaning them and the frame, reg/rect's contact areas will also help!

AFTER doing all of this cleaning, then check your charging system....at idle, measured across the battery, should be about 12 volts, and then should rise up to 14.5 volts at 2500 rpm. If it's not going up to that level, could be an ALT problem, could be a reg/rect problem!
T.C.

[trbig]

As stated, Geezer sells a replacement regulator/rectifier that makes it to where your bike will be putting out a full charge not much over idle.. maybe 1500-1800 rpm versus the 2500. They are a good unit with a lifetime warranty, but they are @ $100 last time I heard.


Tod

[tw1980]

Well if it gets brighter when you rev you know the charging system is working.Try converting all lights to LED.Except the turn signals and head light.You can convert the turns if you get an electronic flasher (2 terminal)but this will disable the auto cancel.There is also a HID head light available but I don't know if it draws less power than the original.

Terry

[boyat68]

It also may be that your battery is a little weak. The flashers will not work properly if the battery falls below 12 volts. As has been stated, this is normal for the standards to have the head light to flare a little as your RPMs increase above 1100 as the charging system starts to put out 14+ volts to keep your battery charged. I honestly believe that the engineers in the 70-80s only meant the head light to be used for others to see you rather than you to see where you were going. I think that their experience was driving in well lit cities.

[dbeardslee]

I have to echo what TC said about cleaning your electrical connectors - and don't forget there are several behind the fuseblock mounting plate, and a bunch inside the headlight bucket. If you find any that appear to have gotten hot, I recommend getting some replacement connectors and housings from Z1, and a crimping tool from Mikes XS. Heat is caused by resistance, and resistance comes from faulty connections. You can clean them till the cows come home, but if you don't eliminate the cause of the resistance you haven't solved the problem. I recently went through my entire wiring harness, and got a little over a full volt back at the TCI. I found that, with each connector I cleaned I was recovering 1 or 2 tenths of a volt. I realize this was ignition related, and your problem is with the lights, but the principle holds for all the electrical connectors. I've also found that it's very difficult to clean the connections while they are still in the housings. It works a lot better if you remove the wires and ends from the housings, but be careful - that old plastic likes to break. Take your time and do a thorough job - it pays off. My $.02

[fredintoon]

Hi Lucien,
to quote Ettienne Bugatti's reply to someone who complained that his Bugatti engine sounded like a bucket of ball bearings being poured onto a steel plate:-
"From what you describe the vehicle is operating perfectly."
Yes, if the tach works and the headlamp brightens above 1,100rpm the charging system is working.
Not that you shouldn't clean & dielectric grease each and every electrical connection there is anyway.
A steady rise in brightness above 1,100rpm rather than a simple change from dim to bright and the flashers not working when the engine is stopped or just idling is a sign that your battery is not at it's best. Try checking the battery fluid levels, topping up with distilled water if required and charging it overnight. See how the flashers etc. work afterwards. If it all works OK, you found the cause. If the symptoms reoccur over time think about replacing the battery.

[Lucien Harpress]

Sounds to me that my problem isn't really that big of a problem. Nice for it to turn out that way (for a change!).

The light I'm not overly-concerned about. After re-adjusting it (so it WASN'T pointed at the sky anymore), there was a marked improvement. The blinkers have a few contact points that are in an obvious need of cleaning, so I hope that solves, or at least helps, that problem.

It'd BETTER not be the battery. I just bought that thing a month or two ago!

The only issue I have left (other than a proper mixture-screw tuning) is an occasional loss of power in the lower RPM ranges. It's not carbs (been though those enough) and I'm pretty sure it isn't a vacuum leak. Someone mentioned before looking at the coils, which is probably next on my "to-do" list. That can wait until I have some more money, though, and the bike is definitely ride-able in the meantime.