C15 Overcharging - I think?

[Stevieo]

Hello everyone, I'm so please to have found this forum and to be accepted as a member.
I have recently aquired my first british bike a BSA C15F 1965

If anyone can please help me with my problem I would be very grateful, the bike seems to be overcharging when idling - Im getting around 8-9v on the battery (its a 6v wired bike).

Some details about the bike, new wiring loom, new stator, coil, reg /rec and battery (sealed 6N63B Powerline) all fitted by previous owner.

There is one wire from the reg /rec that is not connected to anything and it the black one and has 6.5v with ignition on.

There are 5 wires on the reg /rec altogether and are as follows

Red is wired to frame (Positive earth)
Pink is wired to 2x Black / Green wires on loom
Green is wired to 2x White / Brown and there is a 6v on these even with ignition off
Yellow is wired to White / Green
Black not connected.

So my main question is what does the black wire do as I cant see any other reg / recs that have 5 wires inc a pink one?
secondly, is 8-9v too high on idle? it does go down a bit with the lights on though. The ammeter is also to the  far right on idle too.

Thanks for any any help anyway
Steve

[rhyatt]

How many wires are coming from the stator , should be 3.
Is there a name on the reg rec or invoice from the PO
Certainly , your 8 or 9 V are way too high , it will kill the battery.
Try to find the wiring diagram for your reg rec and post it please.

[limeyrob]

The alternator coils can be wired in parallel or series or a mix of both to vary the voltage and output power.  The problem is that modern replacements don't' always have the same wire colours or number of wires as the originals so it may take a bit of working out to match them to the 1960's circuit diagram. Do you have any identification on the alternator stator?

[Derek996]

Most regulators have 4 wires, 2 connecting to the alternator (often both yellow) and 2 output wires, usually red and black connecting to the positive and negative bike connections (earth and battery) Some have a wire loop that gets cut to change from 6V to 12V, or maybe that's the other way round.
A 2 wire alternator connection is simple but a 3 wire alternator requires 2 of the alternator wires to be connected together, either green/yellow and green/black OR green/yellow and dark green depending on the alternator. These are connected to one of the regulator input wires and the green/white from the alternator to the other one.
However your alternator appears to have 5 wires; 2 x black/green, 2 x white/brown and a white/green.
More information about both the alternator and the regulator would help.

[Derek996]

The only rectifier/regulator that I can find with wires as described are replacements for a Honda MTX125 (shown below).
I'd bin that for start and get a known quality one. 6V reg/rectifiers are hard to come by, most are 12V but this is one : https://rexs-speedshop.com/product/6-volt-solid-state-regulator-rectifier/

[limeyrob]

My understanding is that a C15 would not have a regulator, I don't recall one on my B40.

[Stevieo]

Thanks for helping everyone, i work nights so dont always reply during living hours.

OK, stator wires there are only 2 - green/black and white / green - no info on the make or wiring for reg / rec but it looks new. in fact does look like the one posted by derek above.

Not sure what stator it is but its new and a lucas with new rotor, just 2 wires as i mentioned.

Ill try to get info on what I have - im inclined to replace the reg with a more standard one.

Thanks Steve

[Stevieo]

this is the stator and rotor -

[DAVE BRADY]

Hi,

C15s and B40s along with many British bikes had rectifiers fitted as standard.  I think they are referred as 'bridge rectifiers'.
The modern equivalent is the rectifier-regulator which seems to do a good job.
Check out Paul Goff for a 6v one.

Dave.

[limeyrob]

Yes good point, the C15 / B 4 had a rectifier and no regulator.  Later you get the Zenner.

[Tigerfeet]

The original 6v wiring is complicated, with different coils coming it with different switch positions etc.  I did understand it for about fifteen minutes about six months back.

Looking at your picture, that certainly isn't an original 6 volt alternator. I think it highly likely that it is a 12v alternator. (Two wire stators are 12v. Three wire are 6V unless two are joined...)

If the bike has been converted to 12V then the presence of a rectifier/regulator makes sense.

I'm fairly certain that you cannot just bung a 12v stator into a standard 6V loom and simply stick a 6v regulator rectifier in. I had to make my own loom - but I was converting the electrics to 12v. 
Has the bike run successfully as configured for a good while? Or did you buy it with a known electrical issue.  (i.e. 'just needs the wiring finishing...?')

If the previous owner made up his own loom, did he provide a wiring diagram? 

[Stevieo]

It's a new Lucas loom and was sold as a runner. Like I said everything is new, reg l, coil, battery, stator and rotor...so instead of replacing the new stator for 6v, am I better off going for 12v system ?

Btw...the previous owner has said it's done around 100 miles since he restored it

[limeyrob]

I'm more familiar with the C11G -also 6v alternator.  There were some quirks to the wiring:
1 The erg setting on the ignition switch that fed the coil straight off the alternator so you could start with a flat battery.
2 One of the alternator coils routed though the light switch so you got a higher output when the lights were on.
What I do remember is that the battery was either flat or over charged so I'm not sure the system ever worked that well.
There are better ways to wire up the system now.

[V500]

Looks like you got lucky with that alt.
Almost certainly will produce enough juice for a 12V conversion, which makes the wiring a lot less complex. Buy a recommended 12V reg/rect, connect the output to earth and battery and you're good to go.
(Over-simplified I know, but that's the essence of it)

[DAVE BRADY]

Hi,

12v is the way to go. The standard 6V stator can be used for 12v, unless you want lots of output, as it is the battery, reg/rec. that make the difference.
Neg. earth could be done at the same time.
It looks like there is a 10A on the stator so is it 10A output?
Dave.