'72 CB450 Charging System Troubles

Discussion in 'Old's Cool' started by The Jerk, Apr 14, 2008.

  1. Stagehand

    Stagehand Imperfectionist

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    heh good question. quite possibly they list horsepower in Kw also.
    So like 110w, max. With 25w for charging, and originally 25w for original headlight, and about 40-50w or so for ignition, i think, yeah- you're about break even on alternator power. Most of the batteries current is going to go towards pushing the starter motor, unless you add gizmos and bigger lights. With your big headlight, I suspect you're constantly stressing the system.

    I'm curious about your "neutral" setting on the switch, as well, and am trying to follow the wiring to see what it connects and where, to find out what it does. Weird.

    Sorr yIm no real help, I only am familiar and only partly at that with the BMW charging systems, but I assume they all work generally the same.
    #21
  2. The Jerk

    The Jerk Bring us some fresh wine!

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    Lucky for my battery, the electric start doesn't work. The starter motor works OK but the starter clutch is shot. I have a spare but haven't gotten around to installing it yet because it's kind of a pain. So I've been keeping the system stress-free by using only the kicker. :D

    I don't get the N thing either. According to the wiring diagram it looks like it sends power to the high beam & taillight and bridges the 2 charging circuits as the switch does on L. In other words, what the wiring diagram describes as position "N" is really just the high beam position. According to the diagram, H position just powers the high beam and taillight but doesn't bridge the charging circuits. However that's not how it works really.

    My switch, which is definitely the original switch, has no "N" position but the H position on the switch does what the N position on the wiring diagram suggests. Maybe it's some non-U.S. thing but then why would they put it in the U.S. wiring diagram?
    #22
  3. Inane Cathode

    Inane Cathode Cheated Anion

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    As far as i know any honda of that era discharges at idle, you dont actually get any charging effect until 3k rpm or so.
    #23
  4. Stagehand

    Stagehand Imperfectionist

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    I think thats true for any bike that has a crank driven alternator, rather than one that's got its speed stepped up by a belt. Older BMW's dont see any decent juice until then, either.
    #24
  5. markjenn

    markjenn Long timer

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    Great find on the guy producing alternative rectifiers and regulators for our old bikes. This is very cool. I've had no trouble with the charging system on my 71 CB750, but I'm tempted to replace the rectifier and possibly the regulator just as a preventative measure.

    - Mark
    #25
  6. The Jerk

    The Jerk Bring us some fresh wine!

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    OK I'm gonna consider my charging system problem solved. I reversed my previous mod that bridged the split charging circuit all the time and returned it to stock - where 2/3 of charging capability is available normally and when you activate the headlight the other 1/3 comes on line.

    Checked charging current today. With no headlight at idle, around 0.5 amp. At around 3000 rpm a solid 3 amps, right on spec.

    Headlight on, battery is discharging at idle by about 2 amps. However, above idle, in the 2000-3000 rpm range charging current is about 1.7 amps, right on spec.

    So basically the old crappy original rectifier caused all this headache. I should have just replaced it as a matter of course upon acquiring the bike in the first place.
    #26
  7. 41716

    41716 n00b

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    Hi,

    I have the same problem like Jerk and indead this was the reason why I deregistered my CB450K1, MJ. 1968 in 1985. Now, while I'm nearly 60 years old and the CB450 45 years, I' m reactivating it. 30 years ago there was no time to find out the defect.
    Yes, 110W is very low power for such generator, but what I found out until now is as follows:
    The circuit diagram with that pretty colored pathes is helpfull, but also faulty. Instead of the red line to the regulator I have a green one, which is connected to ground! I have two regulators with this wiring (Y, G, Bl) !
    Today I made a bench test with a variable AC power supply, using a simple welding transformer, potentiometer, rectifier, and a dummy-resistor. Findings were two defective regulators! One of them (originally from the sixties) I disassembled/destroyed carefully (the few electr. components are casted with 2K-plastic material in an alloy housing) The findings after that was a defective Z-Diode with very old design.
    Now, my intention is to rebuilt a new regulator with new parts from an electronic parts dealer and than to make some further tests.

    The original rectifier should be replaced anyway, due to the no resistance to vibrations.

    Michael
    #27
  8. Prmurat

    Prmurat Long timer

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    I had the same, exactly, problem with my 71 ( owned since 78) when my wife decided it was hers: she did not rev it up enough and after 40 years a couple of things were old.
    I even had a stator rewinded ( but never installed) but found this:
    http://www.regulatorrectifier.com/catalog/400-450?osCsid=40ce55b571531f2af01bef9ba9fe2be0
    I do not have a 55w headlamp but I have electronic ign ( and there is no way for my wife to not use the ES!) and this gadget is always in the green now:
    Ebay item: 190401283689

    And of course all my wiring is stock: I do not have the knowledge nor the foolishness to think I can do better than Honda R&D !!
    #28
  9. 41716

    41716 n00b

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    Hi Prmurat,

    there is one thing I must say here. It seems to me, that the early CB450's had different alternators. I have two of these alternators here and both show the same electrical power and resistance values, ---and, this is the most important thing, both are too weak to drive a 55W halogen headlight!! The max. output at may be 3000 rpm of the alternator with rectified current is 110W!!!!!! Ignition needs about 30 to 40 Watt, taillight min. 5 Watt. So, the batterie will be discharghed at all using a 55 W headlight bulb. These alternators were installed, as far as I know, on CB450's from 1965 until 1969, which were equipped with only a 25 W headlight.
    After 1970 there was a stronger alternator installed, as far as I know.

    What I did was to install a 25 Watt headlight bulb, which is working together with two high power LED mini headlights which needs only some few mA's. Otherwiese, with only a 25W headlight, I wouldn't like to drive drive this motorcycle!


    Hopefully this link works on US pages:

    it shows the original CB 450 K1 regulator circuit diagram which a crazy guy drawed using CAD. I constructed it yesterday with suscess, --works perfect, but it might be better to use a potentiometer for the R 460 Ohm. So the limited voltage was only round about 13,7 Volt. With a variable 500 Ohms resistor the generator output can be adjusted to 14 Volts.

    http://img191.imageshack.us/i/ladereglerjens.jpg/

    So far, I think or I'm sure that only the electrical problems with the alternator, rectifier and the regulator are the reason why only few CB450K are still existing. The electronic solution for the ignition system is also a good thing, but here were the 2 condensers the problem of the original system. After few years they had only poor capacity. On my CB450K I replaced them now and have a pretty good spark.

    Greetings also to all who drives such a nice motorcycle all over the world

    Michael
    #29
  10. Gene Parmesan

    Gene Parmesan n00b

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    So I'm going to piggy back on Jerk's thread because I'm suffering from the same malady that he seems to have cured. Other than the issue of voltage not rising with the RPMS, I also apparently have an issue of the previous owners jerry rigging the electrical system. I can't say exacty what's going on (I have a mech wrenching for me because I am not mechanically inclined enough, plus no space to work in) but it seems some things are bypassed and hardwired. I should see it tonight and will snap some pics. Hopefully the nice color diagram will clear things up. As you can probably tell I don't own a repair manual either.

    Does anyone know what voltage the generator is supposed to put out at idle and at 3000 rpm? What about once it's rectified? This way I (we... ok, the mech) can test the system piecemeal to isolate the malfunctioning component. Thanks a lot guys!

    Jerk, I see you are in Brooklyn. I am too. If you are inclined to drop some wisdom on me regarding the charging system - the beer is on me. Let me know.
    #30
  11. electroken

    electroken Been here awhile

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    The factory service manual is nearly useless for alternator specs, then they dedicate 5 pages to how a battery works. :huh

    In any of the pre-'74 Hondas, The first thing to replace is the selenium rectifier. Even when they worked, they did not work well. I've seen dozens of failed ones. You can even make your own for $7 from a Radio Shack bridge rectifier (and that's pretty much what is shown in this thread from '08).

    The voltage regulator will last until the sun burns out.
    #31
  12. Gene Parmesan

    Gene Parmesan n00b

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    Thank you electroken. I will get a new rectifier from Oregon Mike. I'll also report on the wiring mess once I have more info.
    #32
  13. MrPulldown

    MrPulldown Long timer

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    #33