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[ASK] motorcycle regulator

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Newbie level 3
Oct 4, 2009
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My motorcycle cann't charge the 12V MF battery because the charging voltage from the regulator only 6Vdc .The coil is OK (13V ac).
does anyone know where i can get honda motorcycle regulator schematic? thanks..

here is the wiring diagram of my bike..
**broken link removed**

On my older dirt bikes and Hondas ('70s CB and CL
series), there appeared to be no regulator at all but
the battery. Perhaps you have shorted cells that
account for the low voltage.

I would suspect no readily servicable parts inside a
regulator assembly, but I'd look for other causes of
low charging voltage before chasing the regulator.

In several cases I simply replaced the battery with a
large electrolytic capacitor to get the bike to run, I
was a "poor college student" at the time with plenty
of access to electronics surplus but very little cash.
Those bikes had no electric start anyway and I saw
no use for the battery (lights work in either case,
though perhaps burn out quicker at sustained high
speed or get dim at idle).

I bet anything after the '80s probably does have a
regulator. But regulators only have so much authority
against limiter alternator current and shorted battery cells.

Measuring the charging current, rather than voltage,
might be illuminating (heh).

last night i've tried to make a simple rectifier and regulator with a bridge diode, a 2SA778, LM7812 and few other cpacitor and resistor.
The main goal of my motorcycle regulator is to make the output voltage around 12.5V, so I added a diode on the LM7812.
The input AC voltage from Coil (stator on The Machine) is around 13 and higher. I've read the datasheet for LM7812 can handle up to 40 Volt DC, so i think it can work for my regulator. But, the result is not like I expected, it cannot regulate steadily.If i raised the RPM (Gas) the DC Voltage otput can reach 17-20Volt.why this can happen?
Somebody pelase help me?.
I'm using the basic LM7812 schematic diagram .

The alternator may be a permanent magnet one and
then the output raw voltage would be RPM-proportional.
A PM alternator will have a fixed current maximum so
a shunt regulator of adequate capacity may be more
what you want - think a 12V zener from C to B of a fat
power transistor (well heat sinked) and a maybe 1Kohm
B-E shunt, C to B+, E to B-.

You want to maybe do a little load-pull on the alternator
at a few RPM positions to determine whether it is a current
limited (so shunt reg is viable) source.

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