Topic: cb450 charging system

[cadler]

CB450 1971
I was checking the voltage at the battery to see if the charging system was working. The voltage was 12.2V at 1Krpm at 4k it is 12.2
both with or without lights. I looked in the book to see where the voltage should be at certain RPMs. The book states that the voltage should remain constant with and without lights at all RPMs.


The current should go up but the voltage stays the same.

Is this right?

I would expect the voltage to go up to 13-14V at higher RPMs
but not according to the book.
Any comments?

[bryanj]

At 12.2 its not charging, BUT you need to be sure youhave an accurate meter

[Bodi]

If your voltage readings are accurate the battery is partially charging but never really getting a full charge. That's basically normal with the older bikes since with no regulator it is actually safer to undercharge the battery rather than "boil" it dry by overcharging. I would expect a slightly higher voltage though, around 13.5 - 14V is what I get with my CB77 which has a similar charging system. I can use the electric start if I stall it in traffic but it's not much use for morning starts.
The system has a permanent magnet alternator with 2 output coils and no regulator. One output coil is always working and provides ignition coil pwer, with the headlight on the other coil is also connected to add the power needed for the lights. The Clymer manual wiring diagrams show the headlight switch wrong, suggesting this extra coil is connected with the headlight off and on low beam but not connected on high beam. (Clymer and Haynes wiring diagrams are crap)
Like any 36 year old bike, the wiring harness connections are probably corroded and reducing the alternator output.
The rotor magnets may have lost "power" and reduced the alternator output.
Installing a silicon rectifier bridge to replace the ancient selenium OEM one would be the second thing I would try after cleaning and tightening the harness bullets and shooting some contact cleaner into the headlight switch.
You could try a different rotor, one from a later year model would at least be "younger". Permanent magnets naturally lose field strength over time and also from physical shocks, so a "younger" one with less miles should be better. I don't know of any place that would/could remagnetize the rotor.

[ProTeal55]

You might wanna look in the headlite bucket and make sure all your wires are connected.
I had a similar issue with my CB450 when we first got it running. Long story short when I ditched all the stock handlebar controls, we just wired the headlite to be on whenever the key was on (ignition). I guess from the factory these bikes were meant to only be at 1/2 charging capacity when the headlite was in the "off" position, and then when the headlite was switched "on" the rest of the charging system would be activated to help handle the extra load. I was running around at 1/2 capacity with my H4 headlite , and then ended up pushing my bike 6 blocks home

Once I found and jumped the wire in the headlite bucket I haven't had an issue...

[mack808]

The most common problem with the older twins, 350s & 450s were the rectifiers failing or the small regulator mounted under the battery box failing. It was very rare to have to replace stator or rotors on those bikes other than from crash damages.. I was working for a Honda dealer back in 72, through 1991......

[frostbackbacon]

You might wanna look in the headlite bucket and make sure all your wires are connected.
I had a similar issue with my CB450 when we first got it running. Long story short when I ditched all the stock handlebar controls, we just wired the headlite to be on whenever the key was on (ignition). I guess from the factory these bikes were meant to only be at 1/2 charging capacity when the headlite was in the "off" position, and then when the headlite was switched "on" the rest of the charging system would be activated to help handle the extra load. I was running around at 1/2 capacity with my H4 headlite , and then ended up pushing my bike 6 blocks home

Once I found and jumped the wire in the headlite bucket I haven't had an issue...

I have the exact same thing with my 74 cb450. No switch and a bit of a charging issue. Do you remember which wires have to be jumped to keep the light on and the system charging?

Thanks.

[tbpmusic]

I have the exact same thing with my 74 cb450. No switch and a bit of a charging issue. Do you remember which wires have to be jumped to keep the light on and the system charging?

Thanks.

Look in the headlight shell, at the wires from the main harness.
You'll see a yellow wire, and a white w/yellow tube. Plug them into each other, the connectors will allow it with no fuss (male/female).
Now you've bypassed the handlebar switch and all 3 coils are in effect all the time, and your 450 is charging as much as it can.
Once the bikes went to lights-on all the time, this connection was made at the factory.
Even when new these charging systems were marginal, producing maybe 3-4 amps if you were lucky.
When you start to add up all the current draws (especially with headlight on), it's clear these bikes are close to the edge in terms of charging. I keep mine on a Battery Tender whenever it's not running. I ride without lights whenever possible, but I live in a rural area and can get away with it.........

[faux fiddy]

I have the exact same thing with my 74 cb450. No switch and a bit of a charging issue. Do you remember which wires have to be jumped to keep the light on and the system charging?

Thanks.

Look in the headlight shell, at the wires from the main harness.
You'll see a yellow wire, and a white w/yellow tube. Plug them into each other, the connectors will allow it with no fuss (male/female).
Now you've bypassed the handlebar switch and all 3 coils are in effect all the time, and your 450 is charging as much as it can.
Once the bikes went to lights-on all the time, this connection was made at the factory.
Even when new these charging systems were marginal, producing maybe 3-4 amps if you were lucky.
When you start to add up all the current draws (especially with headlight on), it's clear these bikes are close to the edge in terms of charging. I keep mine on a Battery Tender whenever it's not running. I ride without lights whenever possible, but I live in a rural area and can get away with it.........

Do you recommend doing this to any 450?  Is there a danger of overcharging the battery?

I had heard of this, and never bothered to do it, but I haven't had any charging issues except when I left the key on.

[frostbackbacon]

I have the exact same thing with my 74 cb450. No switch and a bit of a charging issue. Do you remember which wires have to be jumped to keep the light on and the system charging?

Thanks.

Look in the headlight shell, at the wires from the main harness.
You'll see a yellow wire, and a white w/yellow tube. Plug them into each other, the connectors will allow it with no fuss (male/female).
Now you've bypassed the handlebar switch and all 3 coils are in effect all the time, and your 450 is charging as much as it can...

I went to do this and I don't have these colored wires. I'm going to try and check it out again and see what I have going on. In the meantime, I've ordered a Halogen conversion and an LED bulb hoping to reduce my draw considerably and have a brighter light than the original sealed beam.

[tbpmusic]

Remember, CB450 K5-K7 don't need this, just earlier ones.
Once Honda went to headlights all the time, this change was done at the factory.....

[frostbackbacon]

Remember, CB450 K5-K7 don't need this, just earlier ones.
Once Honda went to headlights all the time, this change was done at the factory.....

So the 74 should be charging on 2 phases all the time then? I've converted the headlight to LED in trying to help keep the draw down. And actually see where I'm going!

Here are the wires I have heading into the bucket.
https://www.dropbox.com/s/s9cdgjzu9yu2hat/2014-09-29%2014.00.04.jpg?dl=0

[Garage_guy_chris]

The stock charging system on the 450s was definately marginal. It doesnt take much for the system to underperform.  My solution on my bike was to replace the regulator / rectifier with a modern permanent magnet combination regulator rectifier. The other modification was to join all the coils going into the reg/rect. Besides that im using a 35w h4 headlight and leds everywhere else and in 4 years i havent had a single problem with it.