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shorted boyer? #70971
08/24/07 10:09 pm
08/24/07 10:09 pm
Joined: Jan 2007
Posts: 14
St. Paul, MN
J
John D Offline OP
BritBike Forum
John D  Offline OP
BritBike Forum
J
Joined: Jan 2007
Posts: 14
St. Paul, MN
Recently completed rebuild of 71 commando and had it running pretty well. Bike then sat idle for a couple of weeks while tank/covers were painted and, upon reassembly, I now find that I have no spark. My electrical set-up consists of a sparxx 3 phase alternator, Boyer electronic ignition, and a 12 volt dyna coil.

The battery appears good - at least it reads 12V on meter. However, I find that both the black and the red (ground) leads from the Boyer to the coil show +12V. Does this mean the Boyer is shorted or is there some other circumstance that can produce this result? If it is shorted, I'd be interested to know what thoughts folks have as to what might have caused the unit to fail.

Thanks.

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Re: shorted boyer? #70972
08/24/07 11:24 pm
08/24/07 11:24 pm
Joined: Sep 2006
Posts: 398
hamilton on. can.
H
highway Offline
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highway  Offline
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H
Joined: Sep 2006
Posts: 398
hamilton on. can.
The reason you have 12 volts on the ground lead is because it is not grounded. Run another wire from the positive (red) to gound. Rick

Re: shorted boyer? #70973
08/24/07 11:27 pm
08/24/07 11:27 pm
Joined: Apr 2006
Posts: 1,708
Virginia, USA
SBoyd Offline
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SBoyd  Offline
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Joined: Apr 2006
Posts: 1,708
Virginia, USA
Do you mean you read 12V between black and red?


Stop the insanity.
Re: shorted boyer? #70974
08/25/07 12:08 am
08/25/07 12:08 am
Joined: Jan 2007
Posts: 14
St. Paul, MN
J
John D Offline OP
BritBike Forum
John D  Offline OP
BritBike Forum
J
Joined: Jan 2007
Posts: 14
St. Paul, MN
There is 0V between black and red from Boyer.

Re: shorted boyer? #70975
08/25/07 1:41 am
08/25/07 1:41 am
Joined: Jun 2002
Posts: 9,879
Scotland
S
Stuart Offline
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Stuart  Offline
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S
Joined: Jun 2002
Posts: 9,879
Scotland
Hi John,

Quote:
Originally posted by highway:
The reason you have 12 volts on the ground lead is because it is not grounded. Run another wire from the positive (red) to gound.
Fwiw, on the Lucas Rita, the fitting instructions advise connecting the amplifier (Boyer-Bransden transistor box) and coil earths (grounds) directly to the battery positive terminal (on a +ve earth system). Although not specifically stated in the B-B instructions, the Bransden Electronics tech. help guys advise the same.

Reason is you avoid the (remote but not unknown) possibility of spikes from another earthed component affecting the electronics, and any possibility of intermediate connections beween component and battery earth terminal breaking down, so the amp./transistor box and coils are no longer earthed/grounded. frown

Hth.

Regards,

Re: shorted boyer? #70976
08/25/07 2:44 am
08/25/07 2:44 am
Joined: Apr 2006
Posts: 1,708
Virginia, USA
SBoyd Offline
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SBoyd  Offline
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Joined: Apr 2006
Posts: 1,708
Virginia, USA
You're still unclear to me.

""I find that both the black and the red (ground) leads from the Boyer to the coil show +12V.""

you read +12V on red, to where? Ground?
If so, the red wire isn't grounded and it should be.


Stop the insanity.
Re: shorted boyer? #70977
08/25/07 12:30 pm
08/25/07 12:30 pm
Joined: Jan 2007
Posts: 14
St. Paul, MN
J
John D Offline OP
BritBike Forum
John D  Offline OP
BritBike Forum
J
Joined: Jan 2007
Posts: 14
St. Paul, MN
I get +12V on the red Boyer output relative to the cylinder head as ground. The same method gives +12V on black lead as well. I get the same result whether the leads are connected to the coil or not.

Re: shorted boyer? #70978
08/25/07 1:43 pm
08/25/07 1:43 pm
Joined: Apr 2006
Posts: 1,708
Virginia, USA
SBoyd Offline
BritBike Forum member
SBoyd  Offline
BritBike Forum member
Joined: Apr 2006
Posts: 1,708
Virginia, USA
John
The red wire MUST go to ground as well as to the coil. (run a wire from ground to the coil terminal that the red wire goes to.) (You will have two wires going to that coil terminal) Then you will not read 12 volts to the cylinder head. Your engine must of course have a ground strap on it to the frame. Otherwise the engine COULD be floating.
All grounds should ideally be tied together at a common point. Probably more important on a Commando as half the bike is hanging in rubber.
The fact that the bike WAS running is irrelevant because ground points are very likely to be intermittent. Don't worry, I doubt very much that the Boyer is shorted. Your readings are normal given that the red lead is not grounded.
(do a search on this forum for common ground or single point grounding. The Boyer is particularly sensitive to this.
>>sb

PS
just re-read your post about painting. Of course one of your ground points may have become painted even though you just refer to body parts which of course should not be used as ground points, but I have seen the rear fender used for such. All ground points must be double-checked to be clean to bare metal, etc., but all the more reason for single-point grounding.

Now, if my ****ing sprag clutch could only be so ****ing cheap and easy to fix.


Stop the insanity.
Re: shorted boyer? #70979
08/26/07 12:32 am
08/26/07 12:32 am
Joined: Jan 2007
Posts: 14
St. Paul, MN
J
John D Offline OP
BritBike Forum
John D  Offline OP
BritBike Forum
J
Joined: Jan 2007
Posts: 14
St. Paul, MN
Tracked it down - as suggested, it was a bad/intermitant ground to the Boyer. Sparks and runs as before. Nothing worse than the new high dollar paint job on bike that won't run.

Thanks to sb and all for feedback and advice.

John


Moderated by  Dave Comeau 


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