BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
  JWood Auction  
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Photo posting tutorial

Member Spotlight
Goostrey
Goostrey
San Antonio, TX
Posts: 21
Joined: July 2005
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
203 registered members (57nortonmodel77), 1,622 guests, and 587 spiders.
Key: Admin, Global Mod, Mod
Newest Members
Doug Baril, revans, Gilly, XTINCT, Bruce Roberts
9960 Registered Users
Top Posters(30 Days)
btour 184
koan58 99
Stuart 85
NickL 70
Popular Topics(Views)
439,657 mail-order LSR
Forum Statistics
Forums33
Topics65,299
Posts632,336
Members9,960
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate This Thread
Page 1 of 3 1 2 3
#624103 - 11/03/15 8:20 am BSA B40 Electric help...a short circuit somewhere!  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Hi Everyone,

A friend of mine has a B40 1961. Was running in perfect order.
He installed a battery cut-switch below the seat. Well, things got bad when he was riding the bike and the switch got shorted by the seat (he needs to loose some weight :))
Well after the short, the bike started to have lack of power, so he changed the battery (old one died with short) but even so the bike was not responding as it should. So he changed the regulator that was also faulty (shorted i think).
Bike now starts ok and runs ok...but when he switches the head light, the engine immediately dies.(like if there was a short there).

I will try to help him solve this, but i will need your help and guidance to point me to the correct direction.

1 - Where can i find the electrical scheme of this 1961 B40?
2 - What would be your first steps to figure the origin of the problem?

thanks in advance
Regards
Goahead

Support Your #1 BritBike Forum!
Membership Type! Free
Member
Premium
Member
Premium Life
Member
Vendor
Member
Site
Sponsor
Recognition No Premium Member Premium Life member (5 years) Vendor Member Site Sponsor Membership
Post commercial threads No No No Yes Yes
Custom title No Yes Yes Yes Yes
Upload avatar & photos No Yes Yes Yes Yes
Link avatar & photos Yes Yes Yes Yes Yes
Private Message Storage: 10 100 100 100 100
Length of signatures 255 600 600 600 600
Removes this very advert island between post 1&2 No Yes Yes Yes Yes
Price Free $12.90/year $105.00 No End
$55.00/5 years
$210.00/year
($17.50/month)
Email
Click on button >>
  Premium Member Premium Life member Vendor Member Site Sponsor Membership
#624112 - 11/03/15 11:18 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Dec 2004
Posts: 8,895
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,895
Scotland

#624115 - 11/03/15 11:34 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Kommando,

thank you so much for the wiring document.

I am having some difficulty understanding the main switch.
To be able to understand how the switch works and find why there is a short (bike shunts down when turning on the head light) I need a better representation of the main switch.

Can you help me get a better diagram of the main switch?What happens to contacts when i turn the key left or right? What pins are shorted?

Sorry for all this questions

Kind regards

#624119 - 11/03/15 12:04 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Dec 2004
Posts: 8,895
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,895
Scotland
Never had a bike with the rotary switch so you will need to wait for another reply.

#624120 - 11/03/15 12:07 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
I think BSA B40 uses Lucas 88SA Ignition.
I sure need the Switch diagram to understand what contacts are connected and disconnected when turning the key to turn on the light

Thanks Kommando. I will wait for another reply

regards

#624126 - 11/03/15 1:53 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal

#624134 - 11/03/15 2:49 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Sep 2013
Posts: 1,583
quinten Online content
BritBike Forum member
quinten  Online Content
BritBike Forum member

Joined: Sep 2013
Posts: 1,583
Pacific northwest
Originally Posted By Carlos


Yes , well close enough , they are civilian models with War Department details .


Has the bike been changed to 12 v ?

The original wiring diagram will show 6 v positive earth .
...which incorporated 'alternator-coil switching' as a method to regulate alternator output when the head light was used . (And coil-switching of emergency-starting too ) ... look Ma , no regulator
.
-------------------------------------------
.
Here is a 12v conversion diagram , using original ? Switchgear .
As you can see :
Switching of alternator coils for lighting
and emergency-starting is eliminated .
The wiring of the ignition switch is now only used as a simple on/off switch with a lot of extra unused positions and poles .

This diagram also shows power going to headlight-switch before going to ignition switch . Whats on your bike could easily be different and work .


.
.
Hope this helps .
.


Last edited by quinten; 11/03/15 3:02 pm.
#624210 - 11/04/15 6:15 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: quinten]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Hi Quinten,

Thank you so much for your reply.
Bike is 6V

I am still confused regarding the scheme. frown
The bike has 3 phase generator and no second switch (the one with the key ON/OFF), only one switch for light (head light case). Thats why he inserted a switch to cut battery connection.

Was The bike changed somehow or it is not from 1961???
I would guess that the correct diagram is nš 808H BSA Service sheet:
http://classicrider.dk/dokuments/ServiceSheets/sectionY_BSAservicesheetno808.pdf

Another quick question:
As i see in the 808H sheet, the phases of the alternator go straight to the switch, lights and ignition coil???
Is the rectifier just for AC to DC or does it makes voltage regulator to?

Can someone explain this (dont need much detail)?


thanks in advance
Goahead

Last edited by Carlos; 11/04/15 6:21 am.
#624211 - 11/04/15 6:41 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2001
Posts: 3,405
gavin eisler Online content
BritBike Forum member
gavin eisler  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 3,405
argyll. scotland, uk
Carlos, it sounds like your wiring has been modified.

"Bike is 6V

I am still confused regarding the scheme. frown
The bike has 3 phase generator and no second switch (the one with the key ON/OFF), only one switch for light (head light case). Thats why he inserted a switch to cut battery connection."

take pictures of the wiring components and post them here..

When you say it has a 3 phase generator , do you mean it has 3 different coloured wires from the stator? this does not mean it has 3 phases, a 3 phase alternator needs a different type of rectifier using 6 diodes.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
#624219 - 11/04/15 8:46 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Dec 2004
Posts: 8,895
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,895
Scotland
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged. There is no regulator only a rectifier. Its not very efficient and best upgraded to 12V and a regulator added and all the alternator coils connected permanently.

#624246 - 11/04/15 12:36 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Hi everyone,

thank you for the kind comments.

Ok its definitely a B40 1961.
It does have a on/off switch, but not with a key.
Like this one.
https://buyvintage1.files.wordpress.com/2010/09/b40_16.jpg

I also believe that the rectifier may not be correctly connected. Maybe my friend didn't know that the bike is positive earth, and something is wrong there...because the rectifier is getting very hot, just like the ignition coil.
I will check that first and wires next.

The scheme posted by Quiten seems the correct one.

Ill keep you all posted when i have more news.

Best regards
Carlos

#624249 - 11/04/15 1:07 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi Carlos,

Originally Posted By Carlos
the 808H sheet, the phases of the alternator go straight to the switch, lights and ignition coil???
Is the rectifier just for AC to DC or does it makes voltage regulator to?

No.

I think you are being confused by the different uses of the English word "generator":- frown

. As I understand it, "the 808H sheet" shows a dynamo - that produces DC (Direct Current) - and its regulator.

. On the other hand, the "Alternator" shown in the two diagrams Quinten has posted generates AC (Alternating Current) which must be rectified by a "Rectifier" to DC to charge a battery. Also, for an alternator to supply AC to an ignition coil directly, the ignition coil must be different from one supplied by DC.

. If "The bike has 3 phase generator" is correct, it can only be an alternator, not a dynamo.

So the first question you need to answer is does the bike have a dynamo and regulator, or an alternator and rectifier?

Originally Posted By Carlos
The bike has 3 phase generator and no second switch (the one with the key ON/OFF), only one switch for light (head light case). Thats why he inserted a switch to cut battery connection.
Was The bike changed somehow

If you have correctly identified the bike as made in 1961, I believe you will find it has and alternator and rectifier, but the switch was not originally an 88SA but a PRS8 (also Lucas). The difference is that there are two versions of the 88SA - ignition or lighting - but the PRS8 is a combined ignition and lighting switch. The original PRS8 broke and a previous owner fitted an 88SA in its place?

Unfortunately, I'm not at home so I cannot cross-check with other diagrams but I believe that the top diagram Quinten posted simply shows the PRS8 in two parts - ignition and lighting - for clarity because it is a wiring diagram.

Likewise, almost certainly the original "generator" was not "3-phase" - I appreciate that the individual wire insulation colours shown in Quinten's lower diagram are the same as the ones Lucas used on the RM24 3-phase stators from 1978, but the two stators are entirely different internally.

If you aren't certain what the bike has, look at the inside circumference of the stator, where you can see the ends of the stator coil cores - single-phase will have six, 3-phase will have nine.

Also see that, in both of the diagrams Quentin posted, the stator has only two connections to the rectifier; 3-phase would require all three wires to go completely separately between the stator and a special 3-phase rectifier.

Originally Posted By kommando
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged. There is no regulator only a rectifier.

Yes and no.

The main problem is the top wiring diagram posted by Quinten contains a misprint so common certainly on Triumph and BSA copies of the Lucas diagram that many people have believed as "kommando" does that only the battery is the regulator in a 6V system. I suspect that, if many worked with those diagrams instead of a Lucas original, if the rest of the regulation wasn't working, most owners/mechanics wouldn't have known it existed. But it does exist and it should work.

What is missing from the diagram is the link from White/Green ("WG") or Light Green ("LG") on the rectifier to terminal #4 on the "Lighting Switch".

With a Lucas single-phase stator, the six coils are connected in three series pairs and the White/Green or Light Green wire is connected to one end of all three series pairs. The Green/Yellow ("GY") wire is connected to the other end of two of the three series pairs and the third wire - Green/Black ("GB") or Dark Green ("DG") - is connected to the other end of the remaining series pair.

When the engine is running and the headlamp is in use, the diagrammed paths from the alternator either through the rectifier or directly (Green/Yellow) to the switches show all three stator coil pairs in use supplying the lights, ignition and charging the battery. bigt

But, when the engine is running but all the lights are switched off, the diagrams appear to show only the one stator coil pair between GB/DG and WG/LG connected to supply the ignition and charge the battery.

If you follow the switch connections carefully, you will see there is another electrical path through the switches from Green/Yellow on terminal #16 to terminal #4; with the wire (WG or LG) on terminal #4 connecting it to the stator, the other two stator coil pairs - that supply the lighting when 'switched in' - are 'short-circuited'; this 'short-circuit' generates a magnetic flux within the stator that depresses the output of the single coil pair so it does not overcharge the battery. bigt When the lighting switch is used to turn on just the "Parking Light/Pilot Light", "Tail Lamp" and "Speedo Light", the electrical path through the switches between terminal #16 and terminal #4 is disconnected, so the 'lighting' coils stop generating the magnetic flux in the stator, so the output of the stator coil pair between GB/DG and WG/LG rises to supply those three small lights. bigt

Hope this helps, sorry it is "much detail". smile

Regards,

#624265 - 11/04/15 2:43 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Dec 2004
Posts: 8,895
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,895
Scotland
Stuart, you need to stop misquoting

I said
Quote:
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged.


which morphed into

Quote:
Lucas diagram that many people have believed as "kommando" does that only the battery is the regulator in a 6V system.

#624271 - 11/04/15 3:42 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: kommando]  
Joined: Sep 2013
Posts: 1,583
quinten Online content
BritBike Forum member
quinten  Online Content
BritBike Forum member

Joined: Sep 2013
Posts: 1,583
Pacific northwest
Originally Posted By kommando
Stuart, you need to stop misquoting

I said
Quote:
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged.


which morphed into

Quote:
Lucas diagram that many people have believed as "kommando" does that only the battery is the regulator in a 6V system.


Lol , join the queue , it goes around the block ,
then west , towards the setting sun ... somewhere just past yonder .

.

#624275 - 11/04/15 4:18 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2001
Posts: 6,904
triton thrasher Online content
BritBike Forum member
triton thrasher  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 6,904
scotland
I had 6V wrecks, back in those days, and never sussed out the shorted coils minimum charge setting until I bought (and soon had to fix, obviously) a new Madras Enfield. That daft bike had the same system at 12V.


Amateur Loctite enthusiast.
#624289 - 11/04/15 5:59 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: triton thrasher]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Thank you all for help so far.

Stuart,

I made a picture to better understand the alternator coils connections with different light switch position...hope its ok:


In another forum, a received help from a user named Arthur (also very helpfull) that send me the wire connections(hope he doesn't mind):



Hope that images are ok..no errors, and they can help others when they came across problems or in bike restore process like the B40.

I hope till the weekend to have my friend problem solved out.
My first bet will be wrong connection in rectifier.
I will post the results here.

Kind regards
Carlos

#624355 - 11/05/15 6:35 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: kommando]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi,

Originally Posted By kommando
you need to stop misquoting

I said
Quote:
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged.

Originally Posted By Stuart
Originally Posted By kommando
6V systems are self regulating wink , the battery acts a crude buffer and the rotary switch tries to match the number of alternator coils working to the load being used, so switch the lights on and more alternator coils are used to keep the battery charged. There is no regulator only a rectifier.

Errr ... do feel free to indicate what I've misquoted?

Originally Posted By kommando
which morphed into

Quote:
Lucas diagram that many people have believed as "kommando" does that only the battery is the regulator in a 6V system.

Errr ... no. The bit you've missed out of quoting yourself is:-

Originally Posted By kommando
There is no regulator only a rectifier.

There is a regulator. I know that Triumph described it certainly in at least some of its manuals. To assist posters, I have described it too, not only in this thread but in several previous threads.

Hth.

Regards,

#624356 - 11/05/15 6:36 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: quinten]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi Quinten,

Likewise, do feel free to indicate where I've misquoted you?

Regards,

#624360 - 11/05/15 7:37 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi Carlos,

I think we are all at the same place. bigt Just to be clear:-

Originally Posted By Carlos

. shows all lights off;

Originally Posted By Carlos

. shows headlamp, "Tail Lamp" and "Speedo Light" on.

There is a third - intermediate - lights switch position, when the lights switch contacts are between terminals #1 & #2, #5 & #6 and #9 and #10:-

. pilot lamp ("Parking Light"), "Tail Lamp" and "Speedo Light" are on;

. because the contact is between terminals #5 & #6, the circuit for the stator 'lighting coil' pairs (between GY and LG/WG) to create magnetic flux is not complete;

. the stator coil pair between GB/DG and LG/WG is supplying those lights as well as the ignition and charging the battery;

. the stator 'lighting' coil pairs are not supplying anything to the bike.

Originally Posted By Carlos

"Lights OFF", the circuit through the two stator coil pairs between GY and LG/WG is through the switch(es) between terminals #16 and #4.

"Tail Pilot Lights ON", there is not a circuit through the two stator coil pairs between GY and LG/WG, but also they are not supplying anything.

"Headlights ON", GY to LG/WG is still a separate circuit from GB/DG to LG/WG; there is not an electrical connection between GY and GB/DG.

Hth.

Regards,

Last edited by Stuart; 11/05/15 8:45 pm. Reason: Incorrect information
#624370 - 11/05/15 9:56 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Dec 2004
Posts: 8,895
kommando Online content
kommando  Online Content


Joined: Dec 2004
Posts: 8,895
Scotland
Stuart, there is no voltage regulator only a control of the output of the alternator via the coil switching but that does not regulate the voltage only tries to balance the output to load, if you replaced the battery with a 50V rated capacitor and revved the engine the voltage would be a lot higher than with a battery even with a lighting load. You can also see the same effect when you put the rotary switch in emergency position, once the battery is full the voltage climbs hence the warning to only use it for short periods.

#624373 - 11/05/15 10:19 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Stuart]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
Stuart,

Is your statement correct?

Originally Posted By Stuart

"Headlights ON", GY to LG/WG is still a separate circuit from GB/DG to LG/WG; there is not an electrical connection between GY and GB/DG.


With "Headlights ON" and "IGN ON" i believe there's an electric connection between GY and GB/DG.
GB goes to Pin7 that will be connected to Pin5 that is connected to Pin18. (Headlight switch ON)
GY goes to Pin17 that is connected to Pin 18 (Ignition Switch ON).

So in fact GY is connected to GB/DG in the above scenario.

Did you mistype or am i missing something?
Isn't my coil drawing correct?

Thank you everyone for all the knowledge shared here.

Kind regards
Carlos

#624454 - 11/05/15 8:50 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi Carlos,

Originally Posted By Carlos
Originally Posted By Stuart
"Headlights ON", GY to LG/WG is still a separate circuit from GB/DG to LG/WG; there is not an electrical connection between GY and GB/DG.

Is your statement correct?

blush No, you are correct; I have amended my previous post.

My apologies, looking at too many circuit diagrams ...

Hth.

Regards,

#624456 - 11/05/15 8:59 pm Re: BSA B40 Electric help...a short circuit somewhere! [Re: kommando]  
Joined: Jun 2002
Posts: 9,301
Stuart Online content
BritBike Forum member
Stuart  Online Content
BritBike Forum member

Joined: Jun 2002
Posts: 9,301
Scotland
Hi,

Originally Posted By kommando
there is no voltage regulator

Uh-uh, you originally posted:-

Originally Posted By kommando
There is no regulator

All I was posting is there is a "regulator" ... or, if you want to be really pedantic, "regulation".

But I didn't misquote you. Or Quentin.

Hth.

Regards,

#624490 - 11/06/15 7:39 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Stuart]  
Joined: Aug 2012
Posts: 61
Carlos Offline
BritBike Forum member
Carlos  Offline
BritBike Forum member

Joined: Aug 2012
Posts: 61
Portugal
OK... Last night i went to my friends house to start the diagnose smile

I found a lot of surprises (loose wires, wrong connections, wrong rectifier etc) but i was able to put the bike running without the lights ON killing engine. hurray.
I must say that now the bike is at the same state when he bought it a year ago...BUT NOT RUNNING AS ORIGINAL! DAME IT!!

The bike still has a big problem. Someone in the past, must have changed the ignition switch from a 88SA to a 63SA. (if someone did not change the switch, then it should not be from 1961 bike?).

Now the "new" symptom (battery is full):

Bike only runs when ignition switch is at EMG position. if i change it to ON, engine dies just like OFF state. Bike does not start at ON position...dead.
Bike running in EMG mode will charge the battery..but probably overcharging it, since it reach's 8.7V with high RPMs.(coils OK?)

Below are the diagrams that i believe are installed in this bike (99% of colors do match the bike):




I follow the wires, and everything seems ok. (but i could have missed something).
Pilot light is connected directly to NW (AMMETER) instead of NG pin11. not an issue..i think.
There is a loose wire in light switch. the NG one, Pin8?? if i recall correctly, but somehow tail light works ok. I will check that next time, and solder the wire back in place, and make the connections as scheme.
I dont think the real problem is here..but i will fix it to its original state.

Here comes the real question:
What can cause the symptom of bike not starting with ignition switch ON, but everything works ok with Ignition at EMG position?

In EMG position, GY wire from alternator is used for + in the ignition coil, in ON position DG from alternator is used for + in the ignition coil.
Bad stator?bad wire/switch?

Please be patient and keep helping me in this.

Regards
Carlos

#624493 - 11/06/15 8:27 am Re: BSA B40 Electric help...a short circuit somewhere! [Re: Carlos]  
Joined: Aug 2001
Posts: 3,405
gavin eisler Online content
BritBike Forum member
gavin eisler  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 3,405
argyll. scotland, uk
Use a voltmeter to check for volts in this sequence.
Across battery terminals, note reading.

Battery negative to frame earth, bare metal any where. Should be the same as the first reading.
This proves the battery positive to frame earth is good.

Battery neg to coil LT terminal ,ign switch off ( no volts), switch on normal position, not EMG, ( volts, but if your problem is in the switch or wiring I think you will see no volts).

If this was my bike I would convert to 12 volts, uses the stock alternator.
Fit a zener diode and potted 12 volt rectifier and use a later model diagram. The alternator switched stator coil system is a nightmare that BSA cured fairly successfully with the Zener diode.

In theory with your stock switched stator coil wiring the EMG position will only work if the battery voltage is low, once the battery volts charge up the bike will miss fire, at this point you switch to normal ignition position and every thing should be OK.
HTH


Last edited by gavin eisler; 11/06/15 8:28 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Page 1 of 3 1 2 3

Moderated by  Allan Gill, Jon W. Whitley 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.335s Queries: 16 (0.056s) Memory: 1.0196 MB (Peak: 1.3999 MB) Zlib disabled. Server Time: 2017-11-24 10:57:37 UTC