Topic: '77 CB550F - Weak Charging System

[HMB550F]

Hello,

For the last month or so I've been attempting to track down a charging issue with my CB. One day, I was out riding, parked for lunch and noticed my bike would barely crank up when getting back on the road. I was able to kick start it, however, a mile from home the bike totally died at a stop sign and would not fire back up. All of the lights on the dash were very dim, as well as the lights. This time, however, it did not have enough power to kick back on. I ended up rolling down a hill, and popping the clutch to get 'er to fire up again. This got me the rest of the way home, but I could not bring engine RPM below 5K, or it would instantly die again. The battery in my bike was old and cheap, so I replaced it with a quality AGM unit. Still, the problem occurred again, so at this point I knew I had a problem with my charging system. The bike is totally stock other than: 1. An aftermarket ignition switch (only a black and red wire are attached to the plug) and 2. an electronic pickup conversion in place of the factory points.

I started by checking voltage. Here is what I found:

Off: 12.7V
On: 11.8V
Idle: 11.9V
3000RPM: 11.9V
4000RPM: 12.0v
5000RPM: 12.1v
6000RPM to redline: 12.2v

So the system is charging if we're technically speaking, but not nearly enough to maintain the battery.

I started by cleaning all of my electrical connections in the battery/chassis area. Some mild rust and corrosion especially around the three yellow wires that connect to the rectifier (riveted in place). No change in voltage when retested.

I checked the resistance of the White and Green wires that route to the stator: 4.5 ohms
I also checked resistance where the White and Green wires connect to the voltage regulator: 1.6 ohms

I attempted to adjust the voltage regulator via the set screw on the side, but three turns in either direction yield no change.

I'd love to get back on the road, but I'm not sure where to look next, maybe the regulator is bad? everything looked clean as a whistle under its big metal dome.

Please share your thoughts.

[scottly]

First, make sure the battery is fully charged. Next, check the voltage to ground on the white regulator wire with the key on, engine not running.

[HondaMan]

Which electronic ignition did you install?

[dave500]

hey,12.2 at red line aint charging at all,a fully charged battery should be say 12.6,running you need say 13.5 plus volts,the system needs looking over,again,it aint charging.

[bryanj]

Most common problem on 550 is the connectors on the yellow wires at generator end and that is not really that common

[HMB550F]

First, make sure the battery is fully charged. Next, check the voltage to ground on the white regulator wire with the key on, engine not running.

The battery is fully charged. I had it plugged in to a charger the night before I ran these tests. With the key on, and engine not running, I read 9.9v on the white wire that comes out of the regulator.

[HMB550F]

Which electronic ignition did you install?

Apologies for not clarifying- one of the previous owners had installed this kit. I'm not sure which kit it is.

[HondaMan]

Which electronic ignition did you install?

Apologies for not clarifying- one of the previous owners had installed this kit. I'm not sure which kit it is.

Can you post a picture of the points plate area (or sensors, if they have been replaced) under the "HONDA" cover on the engine's right side?

[scottly]

First, make sure the battery is fully charged. Next, check the voltage to ground on the white regulator wire with the key on, engine not running.

The battery is fully charged. I had it plugged in to a charger the night before I ran these tests. With the key on, and engine not running, I read 9.9v on the white wire that comes out of the regulator.

What do you read on the black reg wire under the same conditions?

[grcamna2]

Following

[bryanj]

Is the reg original or electronic? 9.6 is too low for the white wire

[HMB550F]

Can you post a picture of the points plate area (or sensors, if they have been replaced) under the "HONDA" cover on the engine's right side?
[/quote]

Turns out there is a sticker on the right side pickup.

[HMB550F]

Is the reg original or electronic? 9.6 is too low for the white wire

Its the original regulator as far as I can tell. Definitely not an aftermarket piece.

[scottly]

That's a Dyna S ignition, but you still have a charging problem. Please post a pic of the reg, with the "set screw" on the side.

[bryanj]

Whats the voltage at the black wire on the reg? Should be battery voltage with key on(dont forget to turn kill switch OFF whilst testing)

[HMB550F]

That's a Dyna S ignition, but you still have a charging problem. Please post a pic of the reg, with the "set screw" on the side.

I'm afraid I did not take any pictures of the regulator while I had everything taken apart. It looked exactly like this, and under the big zinc plated dome were its inner mechanisms including a set screw that put pressure on some sort of leaf spring that had something to do with what looked like breaker points.

[scottly]

Ok, that is a stock reg. Now, what is the voltage on the black wire? Power goes into the reg on the black wire, and comes out of the reg on the white wire.

[HMB550F]

Ok, that is a stock reg. Now, what is the voltage on the black wire? Power goes into the reg on the black wire, and comes out of the reg on the white wire.

Power into the regulator via the female side of the black wire I am reading at 9.9v. This is with the key on, while the battery reads 11.8v, so I am seeing a 2v difference here. One other thing I'd like to mention as that the red wire to the inline glass fuse was getting hot, showing 113F on my heat gun. I imagine this is not normal either. 

[scottly]

The wire getting hot is a sign of a poor connection of the fuse in the clips that hold it. Look closely at the fuse holder for signs of melting in the plastic or other overheating. Sometimes all that is needed is to clean the clips so they make a better connection.

[HMB550F]

Whats the voltage at the black wire on the reg? Should be battery voltage with key on(dont forget to turn kill switch OFF whilst testing)

With the key ON, Voltage on the black wire is 9.9v versus 11.8v at the battery.

[bryanj]

You have a bad connection somewhere in the circuit to the regulator

[Bodi]

The black wire to the regulator does two things: it senses the system voltage and controls the alternator field current to avoid overcharging the battery. It also powers that field coil, switching its power to the white alternator wire.
With only 9ish volts, it will be turning the field coil on 100%. But 9V isn't enough to make a strong magnetic field so alternator output will be very weak, and the battery will discharge until voltage is so low the coils don't spark.
Black wire power goes through A LOT of things and powers a lot before it gets to the alternator. There are several bullet connections, the MAIN fuse and holder, and the keyswitch contacts.
You can switch on (not running) and connect a meter to battery "-" then measure voltage to as many of those spots as can be reached. Main fuse (both ends), keyswitch, coil power terminals, for bullet connections you can slide a meter prove under the sleeve. Any bullets with a brown/black singed sleeve definitely need cleaning and tensioning at minimum, replacement is best.
The coils will be your heaviest draw, but don't leave them powered for too long and overheat them or the Dyna modules. Use the kill switch to shut off just the coils only. Turn the headlight on for more draw, the voltage drop is relative to current - no load will show full battery voltage everywhere in the black wire.
You should find where the drop is along the harness. Most likely is a bullet connection or the keyswitch, wires themselves rarely fail. If you see any green stuff at any connection, the wire copper has corroded and that may be your problem. This also happens if wire insulation is cracked and water gets into the copper, so green goop along any wire is a problem. The corroded copper is not too conductive so it will drop the voltage.
Also measure from battery - to an engine case (with key on and a load on) to confirm the ground is OK. Shoukd be zero volts or a few millivolts.

[bryanj]

Just to add the last test Bodi put in was from battery NEG to engine case

[HMB550F]

The black wire to the regulator does two things: it senses the system voltage and controls the alternator field current to avoid overcharging the battery. It also powers that field coil, switching its power to the white alternator wire.
With only 9ish volts, it will be turning the field coil on 100%. But 9V isn't enough to make a strong magnetic field so alternator output will be very weak, and the battery will discharge until voltage is so low the coils don't spark.
Black wire power goes through A LOT of things and powers a lot before it gets to the alternator. There are several bullet connections, the MAIN fuse and holder, and the keyswitch contacts.
You can switch on (not running) and connect a meter to battery "-" then measure voltage to as many of those spots as can be reached. Main fuse (both ends), keyswitch, coil power terminals, for bullet connections you can slide a meter prove under the sleeve. Any bullets with a brown/black singed sleeve definitely need cleaning and tensioning at minimum, replacement is best.
The coils will be your heaviest draw, but don't leave them powered for too long and overheat them or the Dyna modules. Use the kill switch to shut off just the coils only. Turn the headlight on for more draw, the voltage drop is relative to current - no load will show full battery voltage everywhere in the black wire.
You should find where the drop is along the harness. Most likely is a bullet connection or the keyswitch, wires themselves rarely fail. If you see any green stuff at any connection, the wire copper has corroded and that may be your problem. This also happens if wire insulation is cracked and water gets into the copper, so green goop along any wire is a problem. The corroded copper is not too conductive so it will drop the voltage.
Also measure from battery - to an engine case (with key on and a load on) to confirm the ground is OK. Shoukd be zero volts or a few millivolts.

Thank you for explaining this function. I have started with the ground test, to which resulted in 3.1milivolts. I have began tracing the black wire and have made some strange observations. I believe my wiring harness has been modified to an extent. Only two wires lead to my ignition switch, a red and a black, that simply are connected separately via spade connectors. Inside the headlight, it seems the black wire that leads out of the ignition switch is bundled in with what I can only assume are the wires that were attached to the original ignition plug. The red wire seems to be a totally separate lead from the harness, as if it were bypassing its original connection, to this inline fuse that connects into a bullet junction. This is also the wire that gets hot. Bare in mind, this is how I bought the bike as I haven't touched the electrical system since this problem began occurring.

While I was at it, I went ahead and unplugged my headlight, which at least allows me to make above 12.7v now beyond 4000RPM, so I suppose I could start riding the bike on short trips again while I continue to hunt down this issue.

[scottly]

You have a bit of a wiring project ahead of you! For starters, the leads on the in-line fuse holder are too small. How big is the fuse? Get yourself a blade type fuse holder with heavier leads and some 15 amp fuses.