The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: brissy_bsa on 05.05. 2007 01:18

Title: WIRING HARNESS 51 A10
Post by: brissy_bsa on 05.05. 2007 01:18
Hi all,  I was wondering if anyone could lay their hands on a wiring diagram for a 1951 A10 Plunger. I have had a look at the diagram on the home page and had a look at several others online (all swing arm).  What are the differences with the plunger configuration? Would appreciate any advise.  Ian
Title: Re: WIRING HARNESS 51 A10
Post by: fido on 05.05. 2007 07:18
I don't think there is any difference, though the early models probably had a 45 watt dynamo rather than the later 60 watt version. The harness itself may differ slightly with respect to the lengths of certain wires.
Title: Re: WIRING HARNESS 51 A10
Post by: 1KCBC on 05.05. 2007 08:14
I think the difference is the positive earth or negative earth system.and for my bike used a negative earth.
Title: Re: WIRING HARNESS 51 A10
Post by: a10gf on 05.05. 2007 20:01
and here are the 2 from the 54 manual

http://www.a7a10.net/BSA/manual54/im76-77.jpg
Title: Re: WIRING HARNESS 51 A10
Post by: brissy_bsa on 06.05. 2007 02:57
Thankyou so much for that, I did buy a harness and comparing this with the diagram sent, it doesnt look too big a job........... there is so many people who have suggested I stick with a positive earth and others argue negative is the go........ at the end of the day..... what is the way to go?  Cheers
Title: Re: WIRING HARNESS 51 A10
Post by: a10gf on 07.05. 2007 18:40
Pos or neg? Interesting question, anybody with some ideas? I'm into electronics, I should know, but... Seems the whole world went to neg earth late 50's and trough the 60's, there must have been a very good reason.

I have an idea it started in connection with the use of solid state electrics\electronics, but not sure that was the key reason, must have been may neg earth cars and bikes before that.
Title: Re: WIRING HARNESS 51 A10
Post by: fido on 08.05. 2007 14:39
The change to positive earth was down to a theory concerning corrosion, which is a galvanic reaction involving electrons and ions. It was thought that bikes would rust more slowly if wired with positive earth but in practice I don't think it makes any difference so you can use either system. If you know how the bike was earthed before you could keep it the same. If changing polarity you will need to re-polarise the dynamo.
Title: Re: WIRING HARNESS 51 A10
Post by: brissy_bsa on 21.05. 2007 12:00
Thanks everyone, and now for another question. I am planning to do this bike with a 12V battery,  what do I have to do to all and any other components to achieve this aim?  Once again this is a fantastic font of information, thank you so much everyone. Ian (Australia
Title: Re: WIRING HARNESS 51 A10
Post by: bsa-bill on 21.05. 2007 12:11
as far as I know there are three options

1. The existing dynamo can probably output twelve volts, I don't know all the details but think it involves modifying some of the wiring in the Dynamo and fitting a solid state regulator, others will no doubt comment further.
2. have the dynamo convertd to twelve volts by a professional, this will invlove a rewind and/or fitting a twelve volt armature and regulator, a better option probably
3 fit an Alton altenator, comes with or without belt drive and regulator and relaces your existing dynamo. this is the most expensive option but probably the best.
I am thinking about going down this road ( little pun there  ) so would be interested in anyones experience with an Alton

All the best - Bill
Title: Re: WIRING HARNESS 51 A10
Post by: trevinoz on 21.05. 2007 23:33
G'day Brissy BSA, why bother going 12 volt? you can get 12 volts out of your geny with a suitable regulator but at higher revs. You still only get 60 watts. If you fit correct 30/24 headlight globe and have your mechanical regulator accurately set you will have reasonable lighting. Do you intend to do a lot of night riding?
Another point, on the plunger frame you have to find a battery to fit the battery box. There are 6v types that will fit or you can fit a dummy with a small battery inside. I fitted the dummy on my swinging arm Flash and will do the same on my plungers when I get around to them.
                                                 Trevor.
Title: Re: WIRING HARNESS 51 A10
Post by: bsa-bill on 22.05. 2007 09:29
If you want to go down this route suggested by trevinoz then I would recomend you think about a SRM belt conversion for your dynamo drive.
It's pricey at nearly twice other belt drive kits but it's a toothed belt drive with a steel backed belt that increases dynamo speed by 10% and it works even when the dynamo drive chamber is full of oil, DAMHIK

No connection with SRM at all, just know this is a good product.

All the best - Bill
Title: Re: WIRING HARNESS 51 A10
Post by: brissy_bsa on 24.05. 2007 11:46
thanks guys. yes I intend to modify the wiring in the Dynamo and fit a solid state regulator. Well at least that is the way I am leaning. Ian .