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#613052 - 08/15/15 3:49 pm 1968 BSA Bantam D14/4 Electrical Question  
Joined: Jun 2013
Posts: 66
TonUpTrav Offline
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TonUpTrav  Offline
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Joined: Jun 2013
Posts: 66
Indiana
I have a D14/4 question. I'm having trouble getting spark. However, I stumbled across an odd finding. While turning the ignition switch on and off I am getting spark without kicking it over. When I leave the switch on and kick it over I have no spark. I first noticed the spark while kicking it over and playing with the switch. Thinking it could be a bad switch I hooked up the ignition to the lighting switch and found the same thing. I'm getting spark by simply turning the switch on and off. I'm baffled. Any suggestions would be greatly appreciated. Thanks in advance!

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#613103 - 08/16/15 12:59 am Re: 1968 BSA Bantam D14/4 Electrical Question [Re: TonUpTrav]  
Joined: Jun 2002
Posts: 9,295
Stuart Online content
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Stuart  Online Content
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Joined: Jun 2002
Posts: 9,295
Scotland
Hi,

Originally Posted By TonUpTrav
I stumbled across an odd finding. While turning the ignition switch on and off I am getting spark without kicking it over.

When coil ignition is working normally, you get an HT spark when the points open; the LT - coil charging - circuit is broken, the magnetic field that's charging the HT coil windings collapses and the induced high Voltage is discharged, usually as a spark across the plug terminals.

When you turn on the ignition switch, if the points are also closed, there's a complete LT - coil charging - circuit, so the coil charges up. So, when you turn off the ignition switch, again you're breaking the LT circuit, so you get an HT spark. bigt

Originally Posted By TonUpTrav
When I leave the switch on and kick it over I have no spark.

Which suggests the points aren't opening, or the ignition circuit isn't being broken when they do open; either way, the LT - coil charging - circuit isn't being broken ('til you turn off the ignition switch), which is why you aren't getting a spark?

Imho, points are the Devil's invention as a penance for something really bad you did in a past life. wink Nevertheless, if the points are opening, aiui it's easy to reassemble the parts incorrectly, so the points wire isn't insulated from the points plate, which is why the opening points aren't breaking the LT circuit.

Good luck.

Regards,

#613533 - 08/19/15 1:22 am Re: 1968 BSA Bantam D14/4 Electrical Question [Re: TonUpTrav]  
Joined: Aug 2001
Posts: 111
Mitch Offline
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Mitch  Offline
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Posts: 111
Anchorage Alaska USA
I agree. the possibilities are: points are not opening, a short to ground in the wire between the points and coil, the condenser is shorted, or an insulator on the contact points assembly is missing or in the wrong place (which would ground the coil wire). the last one is easy to do, so if these are fresh points, start there

Last edited by Mitch; 08/19/15 1:23 am.
#613654 - 08/19/15 7:16 pm Re: 1968 BSA Bantam D14/4 Electrical Question [Re: Mitch]  
Joined: Aug 2014
Posts: 309
John Goodwin Online content
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John Goodwin  Online Content
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Joined: Aug 2014
Posts: 309
Bowral NSW Australia
While you clearly have power going to the ignition circuit, I came across this much clearer wiring diagram for the D10,14 & B175's that doesn't have the mistake as per the workshop manuals on the brown wire junction box hook up near the battery that may be of help with other electrical issues on your Bantam.
It's for a modified system using a combined regulator/rectifier instead of the standard bridge rectifier but other than that it's basically the same but a whole lot easier to read.

Hope it's of some help



Cheers John


Current: 2 x 1966 A65S, 1 x 1967 A65SA, 1 x 69/70? A65LA space Y, 1 X D14/4 & 1 x B175
Past: 4 x 1976 T160V, 1 74/5 T150V, 83 model GSX 750 ESD, Z650, Katana 1100(Bathurst Model), 79 T140V, 70's TR6, 2 x 1971 BSA 250 Gold Stars, 50's 350 Goldie, A65 Spitfire semi basket case, 1965/6? A65 LC, Tiger 21 350 & a D14/4 Bantam, 175 Bridgestone Twin with Zimmerman discs!

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