Topic: Electric Ignition/ Coils no spark.

[Bastaldo]

I've got a weird one. I have 1976 cb550 that has been 'brat built.' After a long a troubled relationship with the builder, I got the bike back with some weird problems.

Some background: he installed an all new harness using an M-Unit, that's pretty much set up like the attached diagram. there is a Dyna electronic ignition attached to the original coils (which read 5 ohms). It has new plug boots and wires. The kill switch is gone, it's using a new 12 v antigravity battery, an LED headlight. LED signals, and LED tail light.

here is where it gets weird. Brought it home, and kicked over and started perfect. next day take it out for a ride and, after filling up, feels like it's loosing power and then it looses power. Was able to kick it over a couple of times and then nothing, including all of the lights.

Next day, i test it out and I get spark on the 2,3 but nothing on the 1,4. I check out the harness and find some loos wires that may have shorted, so i cover them and wiggles some stuff around, and all the electric starts to work (lights, horn, signals...) I also pulled the carbs to see if they were gunked from sitting god-knows how long outside, covered or uncovered, in the rain and heat of the summer..... Carbs look fine, albeit I only went into the float bowls.

Next day, I get no sparks anywhere. the rest of the electric still works.

I checked the 1,4 ignition wire (while not attached to the coils) with a test light. Pushed the lobe forward and rotated the crank and got nothing.

Now here is the weird part. See the pic- the 'black' wires on the coils have been soldered together. My guess is that this was necessary to eliminate the kill switch. However, i'm confused as to how the coils are getting their power? (or they aren't and that's why i'm not getting a spark). All the wiring diagrams (both stock wiring and with the m unit) show that each coil has 2 plug wires, 1 circuit wire to the ignition and one 'power' wire. Also, the soldered potion of the coils were like this when i got all 4 cylinders running, so ockham's razor, this isn't it.

So confused!

Thanks for the help.

[TwoTired]

Honda convention is that black wires are 12V switched from the main switch.  I have no way of knowing if a modified bike still follows any Honda convention.

Both coils are fed this 12v at the same time.  Coil operation is controlled by the points or electronic switch connected to Blue and Yellow wires from the stock coils.  They turn the coils ON and active when they complete a circuit to ground or Battery negative terminal.  When the points/Eswitch disconnects the ground connection, the coil sparks the plugs as the coil releases the energy stored in the coils.

Cheers,

[madmtnmotors]

The exposed connection that I see in your picture is indicative of a hack job. Two different colored wires soldered together and exposed, one of which looks like a recycled connector from the old harness? An M-Unit with a "New" wiring harness should be neat and clean. I expect you are going to have to get to know the M-Unit wiring requirements quite intimately and start tracing each circuit. Electrical troubleshooting often requires figuring out what it's not. Electrical troubleshooting will test your intestinal fortitude. On the plus side, if you figure it out you will be better equipped to troubleshoot future problems should they arise.

I recommend a new builder for the next one. You've stumbled across the biggest problem I see with a "custom" build... no service manual. 

[Bastaldo]

Thanks TwoTired!

madmtnmotors- you're telling me! At least i got the bike back... but that's another story.

To bring this back to  basics,the coils get power directly from the m unit NOT from the ignition. As TwoTired pointed out, the ignition/points just complete the circuit. There should be a separate wire feeding to one (if not both) of the coils from another source then the ignition. 

[Bodi]

With a simple digital meter - or analog, if they still exist - you can track down most anything. A simple indicator bulb with wires soldered to it will test voltage and also whether most things are drawing power.
The points need switched power ("aux", I believe, on the M-unit) on one wire, these wires can be soldered together for a custom harness with just one power wire there (the original harness has a splice hidden away that does that I think). The other coil goes to the points or electronic ignition. Your Dyna also needs switched power, if that's off it will act as described - power at the coils but no spark.
The wiring is a mess, agreed. I have to assume that solder joint was taped over at least, but it's a bad idea to switch colors - and a worse idea to swap connector sexes. The harness was set up with a simple rule: "powered" wires all have female connectors (with sleeves) and load wires all have males. That way, a loose powered wire can't casually short to the engine or frame: a male has a metal tip just perfect for that while the female is protected inside its sleeve. The only reason to make that special female-female jumper is because this rule was broken.