Not only do forums denigrade the 70s Honda four charging system, but they also advocate troubleshooting methods that demonstrate the lack of real-world familiarity with these systems. No career mechanic does the things suggested on forums.

Granted, many riders are averse to troubleshooting methodically. They're disinterested in understanding the charging system. They believe in the "silver bullet", the instant fix. It's okay to not have a desire to know. But that makes a person vulnerable to unprofessional forum suggestions. Following is what troubleshooting your CB500/550 or CB350F/400F charging system should look like.

1. Visually inspect all connectors paying special attention to the highest-current ones: the alternator, the rectifier, and the solenoid connections. Any discoloration let alone signs of melting, should be repaired by extracting the terminals (requires a special tool) and cleaning and soldering the wire-to-terminal junctions, then reassembling the connectors. The brass terminals and the plastic connector housings are available from several sources, including Honda themselves (and always have been).

2. Adjust the electrolyte level of a flooded cell type battery, and whether sealed (AGM or Gel) or flooded, charge the battery with a charger capable of at least 3 amps. This is not a trickle or "maintenance" or "tender" charger, note. On the flooded cell battery, do a specific gravity test (look for 1.265). On the sealed battery do an open-circuit terminal volts test instead (look for 13VDC). If need be, recharge and retest. If the above standards can't be met, replace the battery, regardless of how new, where it came from, what it cost, what your brother-in-law says, etc. Don't screw around.

3. Load test the battery using a 2 Ohm, 100 Watt load resistor. This is just as effective as an expensive professional carbon pile tester. Keep your multimeter set to 12VDC on the battery during the test, and after 15 seconds of the resistor adjusted to the middle position, the voltage should not go below 10VDC. If it does, charge the battery and retest. If it still goes below 10V, replace the battery. No matter what.

4. Get a quality multimeter. It doesn't matter whether it's analog or digital. But it needs to have a 10 amp jack. Set up and select the meter for that range. Remove the battery's negative cable. Place the meter leads between the cable and battery negative terminal. Turn the keyswitch on but do not start the bike, and note whether the meter is reading positive or negative current. It should be negative. If it is positive, reverse the meter leads' orientation. Momentarily touch the battery negative cable to the battery negative terminal and start the engine. Or kick start it. Once started, pull the cable away from the battery but make sure the meter is still connected. Let the engine warm up until it will idle without the choke. Let it idle for one or two minutes. Then quickly but smoothly rev to 5,000 rpm and hold at that rpm for only 1 second--no more--and let go. During that second, note what the multimeter reads. A healthy CB500/550 charging system will show above 3 amps.

5. If considerably less, bypass the voltage regulator by putting a jumper wire across the regulator terminals that have a black wire and a white wire attached. Keep the harness wires attached. Then repeat the current test but this time rev to only 2,000 rpm to protect the lights. If the charge rate increases significantly, there is an issue with the regulator. Adjust, repair, or replace.

6. If the regulator bypass makes no difference, un-bypass the regulator and dangle a feeler gauge or large paperclip on a pencil two inches from the alternator and turn the keyswitch on and off slowly, a couple of times. Don't start the bike. Each time the keyswitch is turned on, the feeler gauge should kiss the alternator cover, and each time the keyswitch is turned off, the feeler gauge should relax. This is a magnetism test.

7. If this does not happen, jack and select your multimeter for a resistance test of the charging system's field coil. Test at the field coil's bullet plugs, not at the alternator canon plug. A short, open, or reading higher than the factory's indicates a bad field coil, A good reading on the other hand is unfortunately inconclusive due to the nature of wire coil parts.

8. If a good resistance reading, set your multimeter up for 12VDC and do a volt drop test from the battery positive terminal to the alternator field coil feed wire, the white bullet connector at the bottom of the alternator housing. Don't disconnect anything. Turn the keyswitch on for the test. The reading must be under 1 volt. If more, move the negative meter probe away from the field coil bullet plug to the next connector upstream--i.e., toward the battery--the multiterminal canon plug. Repeat this at each connection point upstream until the reading decreases dramatically. The last juncture tested will be where the problem is. Repair and retest.

9. If instead the magnetism test showed good, then disconnect the alternator connector and using a terminal tool extract the three yellow wires on the alternator side of the connector, and reconnect the connector. Now jumper your 2 Ohm test resistor at its extreme lugs to two of those loose alternator yellow wires, and attach your multimeter set for 25 or more VAC to the same wires, and start and rev the engine to 5,000 rpm. The reading should be 18 volts minimum. Repeat two more times with new combinations of the three wires, looking for the same result within about 10 percent.

10. If your readings from this test are bad, then the alternator stator is bad. Replace it. If the readings from this test are good, then the rectifier is bad. Replace it. I strongly recommend against Chinese replacements. Instead, find a good used factory part, which is how you should approach all electrical parts replacements on vintage Honda sohc fours.

11. After making the indicated repairs, repeat the charge current test, step #4. It is important to confirm the repair and to catch any lingering issues (i.e. more than one problem).

There are a few things to know about this method. First, it is based on a "if this then this" logic structure. You don't do any test unless indicated by the previous test's results. You don't jump all over, testing everything in sight and in no particular order. Second, note that virtually all of these steps are dynamic, that is, made while the charging system is actually operating. Professionals, i.e. those who make their living in the industry, rarely rely on resistance tests. For good reason. Lastly, you must have the test resistor and use it properly.

Forums don't like this methodology. But just because a forum "expert" has an electrical engineering degree or background does not necessarily mean they understand vintage Honda electrical function. In fact, such an individual often disregards the vast difference between theory and practice, and this oversight is never more obvious and more harmful than in motorcycle electrical troubleshooting.