Fitting Electronic ignition? Boyer-you lucky

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Cheers all. Brand new to this forum but no stranger to British bikes. First bike was a 67 BSA Lightning with a rattle can restoration and lots of trips to Sixth Street Specials in NYC. Next bike was a basket case 72 BSA which after I sorted it out sold it for a 72 Bonnie T120. traded that for a 75 Motoguzzi 850T. which I sold to by my pride and joy- My 73 Commando. It's been a year long rebuild and I am nearly complete. But I have trouble with my Boyer. No spark. I have found that at the negative terminal of the firts coil I get a pulse with my test lamp. The coils are wired in series so I should get a pulse at the second coil as well. Nothing. Switched the coils and repeated the test and got exactly the same result. The Black box is sending a charge when the kick start is cranked. I noticed that the coils are slightly crushed by the clamps that hold them under the tank. I'm wondering if there is a way to test the coils other than swapping them in my friend's Triumph. Any suggestions will be appreciated!
 
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Is the Boyer box ground wire hooked with a clean connection and is the motor ground Prefect o? Are you holding the spark plugs being tested hard against the head for good grounding? Are you aware that the boyer shuts down with no impulses from the tripping coils even with the ing. on after some time? Yes the easy test for a coil is replacement with a known good one. Every home shop should have a known good coil.
 
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Thanks for the reply. I will test the engine for ground tomorrow- dang isolastics! Plug was just lying on the head when I tested. I did see a pulse with my test lamp at the first coil, nothing at the second.
 

L.A.B.

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Frank said:
I have found that at the negative terminal of the firts coil I get a pulse with my test lamp. The coils are wired in series so I should get a pulse at the second coil as well. Nothing. Switched the coils and repeated the test and got exactly the same result.

Hello Frank

If there is a fault in either of the coil primary windings then as they are wired in series it will probably affect both coils no matter which connects first. If it was a coil secondary fault then it would be likely to only affect one coil.

If the coil casings are crushed then that could certainly cause problems and is a common Commando problem, try isolating the coil bodies from ground and re-test if you haven't done so already? But they really should be replaced if the casings are crushed and steps taken to ensure the same thing does not happen to the replacements!

Obviously ensure you have a good electrical return wire connection between the engine and frame/battery as the Isolastics are poor electrical conductors.

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If the coils are the standard Lucas 17M6 (6V) type then they should each have a primary resistance of 1.7-1.9 Ohms.
 
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OK! Halfway there. Fitted 2 new coils and tested for spark with plug placed on head. First coil spark positive. Second coil nothing. Will check continuity of jumoer from coil 1 to 2. Wonder why the coils arn't wired paraleell instead of series!!!!
 

L.A.B.

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Frank said:
Wonder why the coils arn't wired paraleell instead of series!!!!

Because the Boyer unit is designed to work using the original coils (thus saving extra expense of buying new coils) which on your model would be 6V, and wiring them in series is the easiest way to do this, and the Boyer works on the wasted spark principal so it doesn't matter anyway. Wiring in two 12V coils in parallel is likely to overload the Boyer box as there is a 3 Ohms limit to the primary coil resistance, which I believe two 12V coils wired in parallel would probably exceed?. Two good 12V coils could be used wired in series according to the installation instructions but I think the spark output is reduced. Some members here use a dual output (Harley) coil with good results.
 
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Thanks to all who responded. Please check my assumptions here: Since the coil that is sparking is connected to the Boyer box by the red ( ground) wire and there are 2 coils in series does it follow that the other coil connected to the Boyer with a black (Hot) wire is A) the 1st in the series circuit and B) current is flowing through it to the next "sparking" coil even though there is no pulse when tested with a test lamp.

I have also checked the jumper between the coils for continuity.
 

L.A.B.

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I think it's time to check the wiring . If both coils work when there are first in line, it has to be something else. Are you sure that you are not somehow sending the first coil to earth before the second coil gets the current?
 
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Thanks for the diagram. I am getting a spark at the second coil. The first coil is connected to the black wire. ????
 
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Yes Frank the black wire idem18 in the directions. It goes to the negative of the first coil. Keep it black coming out of that coil on the positive side because it hooks right up to the negative of the second coil. Now here's the most important part the last positive terminal of the second coil has to have a red positive wire that goes to your common ground spot on the bike. Make a new red wire from the positive terminal of your battery to this spot on the frame. Also make sure that the engine ground goes to the common ground. I always run another red wire into the head light from this common ground. Never trust the frame to do this for you. Have you cleaned you kill switch today?
 
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No Kill switch. Is it possible for the first coil to be faulty and still get a spark at the second coil?
 

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Frank said:
No Kill switch. Is it possible for the first coil to be faulty and still get a spark at the second coil?

If there is a fault in the secondary winding of the non-sparking coil (spark energy shorting to ground through the crushed casing for example) then yes it's possible.

Are you sure there's no short to ground from the coil body/bodies and the frame?

Are you certain that you actually have two 6 Volt coils fitted?

If you swap the coils over does the problem stay with the same coil?
 
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Ignition

One has two coils with the primaries in series, if one primary is shorted then the other will still spark. Each coil is associated with a cylinder, but being a parallel twin, the sparks are simultaneous as long as both circuits are functional.

Mark the coils G(ood) and B(ad) depending on which one sparks. Now physically switch their positions and wire them back up. Basically switching which coil fires which cylinder.

If the spark stays with the G(ood) coil (changing cylinders) then replace the B(ad) coil.

The B(ad) coil has to have a primary that is shorted out.

On the other hand.......

If the G(ood) coil turns bad and the B(ad) coil turns good then the problem is with the secondary wiring which is essentially just the spark plug and its associated cable.
 
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