Topic: Honda cb 500 Four 1976 won’t charge battery

[Lema11]

Hey guys,

My CB 500 is currently not roadworthy. The battery is not charging, so the Honda can only be ridden for about 1-2 km before the battery is completely drained.

The workshop it was recently in couldn’t find the problem. They even installed a used alternator, but without any noticeable success.

Apparently, they checked everything and said it must be the wiring. I’ll have to take a look at it soon… any ideas?

One more question: I can’t find anything about this in the wiring diagram—does anyone know what this part with the green/yellow and red/yellow wires is?

[HondaMan]

I would suggest starting with cleaning the connector blades in the plug that goes from the left side of your electrical panel here, over to the engine. Also, if the bike has been sitting quite a while, the voltage regulator's contacts will probably be a little bit crusty. A points file or some very fine sandpaper will clean them in just a few strokes: they are silver, so they are very soft. Don't sand them too long, or you will wear them down enough to require readjustment of the voltage regulator's set-screw.

It is very common for the contacts in the plugs and the regulator to corrode slightly with lack of use. I always apply a drop of LPS-1 to them, although I am not sure if you can get that in Europe? It is a form of contact cleaner-protector, and is very unique (don't try LPS-2 or LPS-2.5, those are for different things and are more like WD40 penetrating oil).

Do you have an ohmmeter? You can check the field coil of the alternator with that. Post back if you do, and either Bryan or I can walk you through that test.

[scottly]

One more question: I can’t find anything about this in the wiring diagram—does anyone know what this part with the green/yellow and red/yellow wires is?

That is associated with the electric starter safety system, and isn't related to the charging system.
The voltage regulator is behind the fuse block, and has three wires: black, white, and green. The black wire feeds 12v into the reg when the key is on, and the white wire is the output of the regulator that feeds the alternator field coil. With the key on and engine not running, there should be 12v going into the reg on the black wire, and 12v coming out of the reg on the white wire. I would check that first.

[bryanj]

500's didnt have the starter safety thingy only 550.
Non charging has been discussed many times 350,400,50,550 and 750 four all have same charging system

[scottly]

500's didnt have the starter safety thingy only 550.

What is it, then? The later US models used a diode instead of the SMSU, which is what I guessed that to be based on the wire colors. Of course, there were no 1976 500s here, only 550s by that time.

[bryanj]

I have no idea how or why its there, uk had Ki 500 right up till 76 as well but they never had it only the 550F and K3, we didnt get the earlier 550

[HondaMan]

Hey guys,

My CB 500 is currently not roadworthy. The battery is not charging, so the Honda can only be ridden for about 1-2 km before the battery is completely drained.

The workshop it was recently in couldn’t find the problem. They even installed a used alternator, but without any noticeable success.

Apparently, they checked everything and said it must be the wiring. I’ll have to take a look at it soon… any ideas?

One more question: I can’t find anything about this in the wiring diagram—does anyone know what this part with the green/yellow and red/yellow wires is?

Yellow/Red is Starter control (to the Starter relay), but you'll have to trace the Grn/Yellow to figure out where it comes from? Maybe check the clutch lever for its switch wires: see if the Grn/Yellow goes active when the clutch is pulled in?

Honda set these up so that the starter would not run if the clutch lever wasn't pulled if the bike wasn't in Neutral (you have to pull in the clutch to run the starter unless the tranny is in Neutral),

[scottly]

I'm not really sure if that's a diode, but the colors of the wires are related to the starting circuit, and have Nothing to do with the charging system!

[rotortiller]

can only be ridden for about 1-2 km before the battery is completely drained.

A charged serviceable battery should last way longer than 2 kilometers even with the alternator unplugged. The first thing I'd do is charge and check the battery condition. If it fails or has low capacity time for a new battery. You could also hook up an amp-meter to check what the bike is asking for under a static condition (engine off, key and kill on), maybe there is a short or a component using way too much current. Around 10 amps at 12V is a ball park figure for something like this with the headlight on. Next I would use a voltmeter to check the system voltage while running at a decent rpm say 3500-4000. Those results would then determine my next actions. The 500 engine must have been transplanted from the subject title.

[scottly]

can only be ridden for about 1-2 km before the battery is completely drained.

A charged serviceable battery should last way longer than 2 kilometers even with the alternator unplugged. The first thing I'd do is charge and check the battery condition. If it fails or has low capacity time for a new battery.

Valid point.

[Lema11]

Thanks for all your feedback. Yes, I have a multimeter and will test the components. The ignition switch is almost completely broken, so I ordered a new one. It should arrive today or tomorrow. I even already have a combination unit of rectifier and regulator (it was given to me by the previous owner). In case something is broken.

The battery should not be in best condition, so that’s also something I’ve ordered. I did not mention , that the bike is running pretty unstable, after kicking it for like 10min. (Even with cleaned carbs and everything)