Happy to share how I would do it.

1. Check the alternator brushes to make sure they haven't worn to the minimum length.

2. Check the 3 connections on the voltage regulator to make sure they aren't corroded and are making a good connection.

3. Check the battery for water level and terminal cleanliness.

4. Electrical power has 2 parts: voltage and current. If the bike runs OK and the standard lights are bright, then the voltage is probably OK. You'll then need a DC ammeter to check the current going into and out of the battery. The ones that work best are the analog "center zero type" with fine graduations. Here's a photo of the one I've been using since 1971.

My little ammeter

As you can see it's not special or expensive. You simply connect this between one battery terminal and the battery lead. This meter will reveal the story of the current going in (called a "charge") or out (called a "discharge") of the battery.

Gathering the Data
1. With the engine OFF, turn the ignition ON and record the "discharge". Then add the lights in succession, starting with Lo beam, then Hi beam, then each of your running lights and electrical accessories one at a time, recording each of those readings.

2. Then kick start the engine and take the exact same readings at 3000+ RPM, only this time we should see the meter swing to the other side of the scale and show a "charge" with every added light and accessory. The reading of the charge current will obviously get smaller as more accessories are added, but the readings must always remain positive. Record all these readings along side the first set.

NOTE: We do not take readings with the horn, turn signals, or brake lights being used because these accessories should be used on a very limited basis equaling about ~1/50 of our total ride time.

3. The last reading is to return to Hi beam only. With the engine idling the meter should show a discharge. Slowly raise the RPM of the engine while watching the meter. Record the RPM at which the meter reads just above Zero.

What This Tells Us
1. With the engine OFF you should see a slowly progressing current demand, ending with a reasonable maximum current draw. For instance, -1A for ignition only, -5A for ignition + Lo beam, -7A for Ignition + Hi beam, and maybe a maximum of -10A with all the accessory lights ON.

2. With the engine running (and therefore charging) the alternator should be able to override each discharge condition. For instance, with ignition only +3A, with Lo beam or Hi beam ON +2A, and of course at least +1A with each and every successive accessory light.

The light or accessory that will not allow the ammeter to stay in Positive ("charge") territory is the accessory you cannot use. Sometimes the ammeter may show you this is a certain combination of accessories, like fog lights AND the heated vest. You get to use one or the other, but not both simultaneously. I also see a lot of cases where the driving lights were OK until the original 50W headlamp bulb was swapped for a 80W headlamp bulb.

3. What this test shows is the minimum engine RPM you should ever be riding. Hopefully your normal engine speed is at least double that.

There Are Always Limits
The ammeter doesn't lie, it helps you come to terms with your electrical needs and make better "budgeting" decisions about how you'll use your limited current availability.
• Maybe you could keep the 65W main headlamp bulb IF you converted your driving lamps to modern low current LED lamps.
• Maybe you really don't need 67 incandescent tail lamp bulbs. Maybe some red LED strips would be just as bright and use 1/10 the current ?
• Maybe a windscreen and heated grips is a better use of power than the 80W headlamp bulb + heated vest + heated socks + tape deck ?
• Maybe due to so much slow, in-town riding using blinkers and brake lamps, you will need to reduce your headlamp wattage back to the OEM wattage ?
• Maybe your in-town rides are so short (very short battery charge times) that you ought to be using your kick start more and your electric starter less ?

There are many parallels between your checking account and your electrical system. You certainly can't buy every toy you see, and you can't install every electrical accessory that's advertised.

Hope this helps. 🙂

Thanks so much for the response. I will go down the check list and get to the bottom of it. I have learned a ton from the site, this is one more experience of the help. Best to you. Cliff

Cliff -
As I said, there are many parallels between your family checking account and your motorcycle's electrical powder budget. You cannot think your way out of debt, you must sit down and make a written financial budget and exclude all unnecessary spending.

In the same way, you cannot think yourself out of a discharge situation. This is especially hard because although you can see the money you spend, you absolutely cannot see electricity being consumed. So you must use a meter and physically measure the current each accessory consumes.

Hope this helps.

This has been a huge help. Now you think we can spend a few moments assisting me with my check book?? I will get the electrical all worked out, the banking after 5 kids thru college is another matter. LOL Really appreciate the help. Cliff

I will get the electrical all worked out, the banking after 5 kids thru college is another matter. LOL Really appreciate the help.

With 5 kids, it sounds like you really did need some help, brother.

In my next installment we'll discuss what's causing those kids ! 😛

If your /5 has the original alternator configuration, you can gain around 100 watts of output by installing the stator, diode board, and related extra wiring from a /6. However, even if you did this upgrade, you would be well advised to follow wobbly's check list to determine and re-assess the demands that your accessories place on the charging system.

One last thought; when puttering around town, use a lower gear to keep the motor RPM's up. This will ensure that your alternator is delivering the maximum current it is capable of producing. For a number of reasons, you want to keep the RPM's at or above 3000.

I sure would like to know more about these "highway lights"....
• What is their wattage and how many of them are there ?
• Is everything fine if they remain OFF ?
• Where does the problem exhibit itself... around town or on the highway ?
• Are these lamps wired so that multiple lamps are controlled by a single switch ?

The lights came on the machine when I bought it a year ago. Everything works perfectly but the amp draw of these two lamps is heavy I will check the wattage of the lamps and get back to ya. They work off of one switch and since, my one bad experience, I use them VERY sparingly. I only run them when I am spinning pretty good, at higher rpms. I missed bidding on a full stator set, diode included on ebay just this week, '75 R65/6. I forgot all about it. What a jerk I am!! I am still a bit new at doing this work myself. At 61, I am just a plebe. I have an ammeter so I am going to follow all instructions and figure this. Updating with /6 will probably take care of all.
Was 60 degrees here in NYC area, almost ready. Thanks for reaching out men, appreciate it.

► I ask because there are several typical scenarios at play here. You may not need high dollar parts at all...

• Someone may have forgotten to disconnect the battery when removing the front engine cover. If there was an arc to the case, one of the diodes on the rectifier board could be blown. That would reduce the current output considerably, but not affect the system voltage. So you may only need a diode board.

• When these bikes were new all that was available was a 55/55W headlamp bulb (3.9A). These days you can get a plug compatible 80/80W bulb (5.7A) to go in there. People fit those all the time without thinking, but that's a huge jump in current consumption ! It's also 1.8A that's not being used to charge the battery any longer !!

• Then there's the addition of high wattage highway lamps, which we already discussed.

• There's also the discussion of YOUR typical riding habits. Do you go for long rides with few uses of brake lamps and blinkers, or do you putt around town with constant accessory lamp use ?

• Is your brake lamp switch adjusted correctly ? Is your brake lamp ON while you ride ?

An accurate ammeter will sort these things out really fast.

► Short-cut interim suggestions...

• Is there any way to put each highway light on separate control switch ?

• Replace your 4W parking lamp bulb with one of the 20W "daytime running lamp" bulbs. Then use your parking lamp during the day and only run your full headlamp at night.

Hope this helps.

Thanks for the help me. I have a full '75 stator unit on the way. 20 amps along with a rotor, diode and condenser. You guys were more than helpful, hope I can reciprocate down the road, so to speak. I bought it for a really good deal, and no matter what, as we say around here near Brooklyn, "It can't hyte!!" Ride safe, here comes the nice weather. Cliff

Well, that should certainly fix it !! Good luck, my friend.

Just wanted y'all to know. I followed all the instruction offered. Finally I bought a used "75 slash 6 Stator and rotor and diode and condenser. The bike couldn't be charging better. Few battery charges. Runs auxiliary lights. Bike is much happier and so am I. Thank you Airhead world. Sincerely, Cliff