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71 Bsa thuderbolt wiring
#627021 11/23/15 10:05 pm
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I am restoring my first BSA. I am struggling on the wiring. I purchased a new harness so I have a lot of questions and need guidance. I am putting in an Accel 140405 coil in place of my original two coils. Based on that I do not know what color wire go to what side .

Do I still need a zenar diode?

My wiring diagram show a 3 position ignition switch but the original was two position?

Also, do I still need a rectifier?

Most everything else is connector

Thanks for any help

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Re: 71 Bsa thuderbolt wiring
bezza Tim #627029 11/23/15 11:16 pm
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Tim, what year BSA?

A dual-fire coil usually accompanies an electronic ignition system, since those produce a spark on every cycle, with a "wasted" spark on the cylinder that's on the exhaust stroke. I've heard it's possible to use a dual-fire coil with a breaker point system, but I haven't seen an example of this in practice. Maybe others can elaborate on this.

Yes, you still need the rectifier and the zener diode, unless you replace them with an aftermarket rectifier/regulator unit.

The wiring diagram may cover some number of years. The ignition switch was changed to three-position at some point. Just make sure you're looking at a pre-1971 diagram, the '71-'72 wiring is quite different. The three position switches were usually wired: Position 1 = OFF, position 2 = ignition ON, and position 3 = ignition and lights ON. A two-position switch powers both circuits on and off together, so you rely on the headlamp switch to turn off the lighting, which is more or less necessary for starting. If your harness has three terminals for the ignition switch, just join the two "load side" wires, to ignition and lighting.



Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: 71 Bsa thuderbolt wiring
bezza Tim #627036 11/24/15 12:08 am
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Thanks for the quick reply. I should have added I am putting in a Boyer electronic ignition. Based on that do I need the zenar diode and rectifier? Thanks

Re: 71 Bsa thuderbolt wiring
bezza Tim #627041 11/24/15 2:08 am
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Originally Posted by bezza Tim
I should have added I am putting in a boyer electronic ignition. Based on that do I need the zenar diode and rectifier? Thanks

The Boyer only replaces and replicates what the points do , which is ignition management .
... with a maintenance-free signaling device , where the points sit ,
and a circuit-board advance-management thingy in a separate 'box'.
..........................

The rectifier /zener combo is managing something unrelated to the ignition , the output of the alternator.

The alternators AC output must first be rectified to DC
before the battery can accept it .
And a zener caps and gates the DC voltage to a level that protects the battery from overcharging and light bulbs from blowing .

A modern regulator/rectifer 'box'
replaces the rectifer/diode bits and functions in a compact package .
That if working as designed , is more efficient .

These are 2 separate upgrades
that can be done
together or separately .
... And will require some modification of a stock harness

IS there a harness on the bike now , and is it good enough to start copying the wires placements as you rewire ?

.



Re: 71 Bsa thuderbolt wiring
bezza Tim #627091 11/24/15 12:51 pm
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Tim, the original 71 ignition switch was three position. Off, On without lights and on with lights.

Bill E


69 A65T
71 B50T
85 K100RS
54/59 A10SR
69 B44VS
71 A65FS
95 Trident
Too much moderation is bad for you.

Re: 71 Bsa thuderbolt wiring
quinten #627107 11/24/15 2:44 pm
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Thanks for all your help in explaining the differences and needed parts.

I am putting on a new harness. The old one is completely off the bike.

Re: 71 Bsa thuderbolt wiring
bezza Tim #627352 11/26/15 11:04 am
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Ok. Now wiring my new accel coil. When I look at my wiring harness and diagram I have wire coded BY , BW, WY, and a bunch of R. My accell coil is a 140405

What wire gies where?

Re: 71 Bsa thuderbolt wiring
bezza Tim #627357 11/26/15 11:37 am
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"Just make sure you're looking at a pre-1971 diagram, the '71-'72 wiring is quite different. The three position switches were usually wired: Position 1 = OFF, position 2 = ignition ON, and position 3 = ignition and lights ON. A two-position switch powers both circuits on and off together, so you rely on the headlamp switch to turn off the lighting, which is more or less necessary for starting. If your harness has three terminals for the ignition switch, just join the two "load side" wires, to ignition and lighting."

That is confusing.

The OP has a 1971 A65 . He needs a 71 diagram, the twin coil will work with a Boyer Ei. not with points.,

the yellow / white is the live feed to the ignition from the kill switch.
The reds are common grounds earths which are positive on this model.
Black yellow and blacjk white are the wires from the points , stock they connected to the coils, if using ei they go to the box of white mans magic.

Your twin coil will work with EI, dont think it works with points, you need a rectifari and a Zener diode, or get a " power box" that does both rectify and regulate.

original 3 position key switches are like hens teeth , a two position is the simple and available replacement, the switch on the lamp bucket powers the lights , when the key switch is on.

If you dont know AC from DC or own a multimeter and know how to use it, go to someone that does.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: 71 Bsa thuderbolt wiring
bezza Tim #627378 11/26/15 1:06 pm
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I am using a 71-72 wiring diagram. I am using a Boyer EI. I ordered a potronics solid state rectifier/zenor doide yesterday. I believe now I have everything covered for now.
Appreciate everyone's help!!

Re: 71 Bsa thuderbolt wiring
gavin eisler #627390 11/26/15 1:58 pm
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[quote=gavin eisler
That is confusing.

The OP has a 1971 A65 . He needs a 71 diagram, the twin coil will work with a Boyer Ei. not with points.,

[/quote]

Sorry; I read back through the thread and nowhere do I see where Tim said he has a 1971 bike. The mention of a two-position ignition switch led me to believe it was an earlier model. Nevertheless, if he has a two-position ignition switch, the wires that feed the ignition and the lighting both need to be connected to the load side of the switch - logically, that is; not necessarily right at the switch. (It CAN be right at the switch however if the switch has a double terminal.)



Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: 71 Bsa thuderbolt wiring
Mark Z #627413 11/26/15 4:19 pm
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The wire(s) from the key , that on a stock harness ,
would have gone to the coils ,
Now go to the Boyer box .
( there are 2 white wires in the harness , one is used , one is capped)

Power to the coil/s , now comes from the Boyer box .
.
[Linked Image]

.




Re: 71 Bsa thuderbolt wiring
bezza Tim #627432 11/26/15 6:02 pm
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Very good but I would have put the fuse after the parallel link of the battery and capacitor. Otherwise if the fuse blows because of a short you will still burn your look into flames because the capacitor will continue to run the bike.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: 71 Bsa thuderbolt wiring
bezza Tim #627504 11/27/15 2:40 am
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Ok. Do I attach my stator wires to the potronics and then to the Boyer box?
Thanks

Re: 71 Bsa thuderbolt wiring
bezza Tim #627512 11/27/15 6:08 am
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[quote=gavin eisler
That is confusing.

The OP has a 1971 A65 . He needs a 71 diagram, the twin coil will work with a Boyer Ei. not with points.,

[/quote]

Sorry; I read back through the thread and nowhere do I see where Tim said he has a 1971 bike

its in the title "Re: 71 Bsa thuderbolt wiring


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: 71 Bsa thuderbolt wiring
bezza Tim #627513 11/27/15 6:10 am
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Stator wires to podtronix, , Ei fed from white / yellow from kill switch. Black yellow/ white points pair to Boyer.Look at the Boyer diagram above, substitute the white live to the Boyer for the white / yellow and you have it.

Last edited by gavin eisler; 11/27/15 6:12 am.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: 71 Bsa thuderbolt wiring
bezza Tim #627579 11/27/15 5:38 pm
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There will be extra wires on a stock harness the Boyer ignition will not need or use .
The harness will have 4 wires exiting for the coils ,
only one of these wires is needed to power The Boyer box .
In this bunch , There is a pair of w/y wires , use one of them to power the Boyer .
The other 3 wires get capped . ( as do any remotely fitted condenser wires)... and points wires.
This pic is for the right year , but not specific to your bike , I could not pull up a high enough
Resolution image of your harness to be useful.
I believe ? , It is extremely similar.
[Linked Image]

The zener diode wire is hot , remember to cap it off .

Thank you classic British spares ,
I believe ? This is an acceptable replication of a public image ?


Re: 71 Bsa thuderbolt wiring
bezza Tim #627582 11/27/15 5:42 pm
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It's a good way to present a wiring diagram, that's for sure! It sort of makes sense when it's drawn like this ....

Lannis


"The urge to save humanity is almost always a false-face for the urge to rule it."
Re: 71 Bsa thuderbolt wiring
bezza Tim #627641 11/28/15 6:11 am
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Quote
a good way to present

I also like it!
This will save me a lot of measuring time.

Looking better... in the rear end (RH-side) there's a brown wire going to a "Stop Lamp".
That's clear, the armature on the rear fender.

But the brown wire on the rh-side of the group of wires up front?
That one goes to a what is called a "Stop Light".

Where does it connect to?

Last edited by Ger B; 11/28/15 6:53 am. Reason: a late question

Ger B

Re: 71 Bsa thuderbolt wiring
bezza Tim #627645 11/28/15 8:36 am
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Awesome!

Re: 71 Bsa thuderbolt wiring
bezza Tim #627648 11/28/15 9:14 am
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The pictured loom will not suit a 71 A65 ( note it is labelled 70 -72 T100, which have components in different places). , the zener moved from the front to the middle at the airbox, the points spur pair needs to move rearward as well.
No idea what the front "stop light" brown core is for . possibly the hot feed to brake lights switches from the ignition switch.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: 71 Bsa thuderbolt wiring
bezza Tim #627653 11/28/15 9:33 am
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Quote
will not suit a 71 A65

I think I was overexcited... blush

I wonder if there is a drawing like this for the 71-A65.


Ger B

Re: 71 Bsa thuderbolt wiring
Ger B #627656 11/28/15 10:08 am
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Originally Posted by Ger B
Quote
will not suit a 71 A65

I think I was overexcited... blush

I wonder if there is a drawing like this for the 71-A65.


http://www.feked.com/genuine-lucas-main-wiring-harness-bsa-a50-a65-1970-72-lu54960710.html

Re: 71 Bsa thuderbolt wiring
L.A.B. #627681 11/28/15 12:08 pm
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Here is the correct harness , resolution is not that good , but may be good enough .


[Linked Image]

Re: 71 Bsa thuderbolt wiring
bezza Tim #795538 01/13/20 7:32 pm
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Quinten

your 1971 wiring diagram appears to have expired. Can you post it again?

tks

Gary


1969 A65T BSA

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