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Charging

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SteveD CB500K0:
Thanks for posting that. I tend to forget that we're not all (ex) electronic/electrical engineers on here!

I also have an AVO (its an ancient Model 40 that I inherited from my father who was a real "electrical" engineer. I also have a Fluke digital which I "inherited" from my last employer...)

BigAl (Alan):
Hi Tristan,

If you can get hold of My CB 750 Book By Mark Paris page V-10 his explanation with drawings will make things a lot clearer.
The disadvantage with the field coil is that it is using 2 amps @ tick-over (no current is fed back into the battery until 2-3K revs) so if the battery is not fully charged and you put the lights on @ tick-over the voltage drops further...the ignition coils have reduced power to produce a good spark...and then stalls.
You will need a multimeter (ideally an AVO, has 10 amp full scale reading) and some circuit knowledge to find out the voltage or better still the current being used
PS The voltage regulator switches ON or OFF or part ON the field coil

Alan

Fairview:
Further to my previous post......

Although the battery seemed to hold charge when left overnight it did seem to drain over longer periods and I wasn't convinced that it was sound. I'm fairly sure it isn't the bike draining it but its old so I spunked 40 quid on a new one today (based on Madoc's comment that the charging system is dependant on a decent battery) and ran the tests again. This is what I got -

Ignition off - 12.6v
      "     on - 11.96v
Tick over   -  12.2v
3k rev      -   12.5v
3k & lights -  12.6v

I think this suggests a charging problem? If so where do I start.....

Thanks in advance.

madoc:
Ok.
I know it sounds droll, but thirty years of bikes always lead me to suspect the regulator.

Anyway , it's either alternator, regulator/rectifier or wiring.

I would check the alternator first and eliminate that.
According to the workshop manual, you can run a resistance check across the three yellow wires:
http://www.scribd.com/doc/14355713/Honda-CB500-CB550-workshop-manual  (page 95)
You maybe want to check to earth as well.

If it's good then check continuity through the loom to the regulator and rectifier (which are separate parts under the left hand side panel).

To be fair, if both alternator and wiring are ok then I'd just replace the original mechanical reg and separate rectifier with a solid state one (what I did).  I got one for £30 and it used the existing mountings and had the right connectors.

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