4 Volts on Coils (no spark)

[Rafe]

Just replaced my headlight and now I have no spark. Double-checked all my harness connections and they look good. Measured 4 volts on both of my ignition coils. Last year they measured 9 volts. Has anyone ever seen this drop in voltage?

[tom203]

Just replaced my headlight and now I have no spark. Double-checked all my harness connections and they look good. Measured 4 volts on both of my ignition coils. Last year they measured 9 volts. Has anyone ever seen this drop in voltage?

Did it run last year with 9 volts to coils? where and how are measuring this voltage to coils? Headlight replacement seems an unlikely culprit!

[mike_of_bbg]

It was lucky to be running with 9V at the coils. 4V it's definitely going nowhere. What did you replace your headlight with? Might be time to do a coil relay mod. Try removing the headlight and measuring the voltage again to verify correlation.

The kill switch is a frequent cause of voltage drop at the coils. Be careful though if you take it apart to clean it: there's a spring loaded contact that's easy to drop/lose. Even after cleaning mine and some connectors on the harness I could only get back up to 9.2V (from 8.5V) and ended up doing the coil relay mod.

[Rafe]

Did it run last year with 9 volts to coils? where and how are measuring this voltage to coils? Headlight replacement seems an unlikely culprit!

Yes, it ran fine. I used a multitester on both positive connections on each of my coils and ran the negative probe on the engine block. I was thinking that I maybe reconnected something incorrectly on my harness but after rechecking all the colors are matching up. I'm sure its something very simple, just not sure what.

[Rafe]

Try removing the headlight and measuring the voltage again to verify correlation.

The headlight's off. I replaced the entire bucket, and in order to do so, I disconnected everything. So that's what i'm thinking is the culprit. But everything looks in check.

[Rafe]

I'm going to start disconnecting all electrical devices and measuring voltage off of the coils to see if it changes. I may have a short somewhere.

[mike_of_bbg]

Are you checking against a wiring diagram? There's probably one in the service manual on BC's site.

[spyug]

Try again with the negative probe directly to the negative terminal on the battery. I've noticed faulty readings using the method you used.

If you are having such low voltages there really is something seriously wrong and I would be highly suspect of a a faulty battery. I'd also recommend the coil relay mod in any event.

Good luck sorting it.

Cheers,
spyug

[Rafe]

This is where i'm at...srry 4 the bad picture. I have 3 wires on the right, 2 of which come from the coils. The 3rd wire reads 12V, but when I connect the wire on the left, the reading drops to 4V. All these wires are Orange and White and they were all connected together with a crimp-on connector. I'm at a loss, because if I do the relay mod here, the wire on the left will just drop it down to 4V. Any help will be appreciated.

[Matchless]

Have you checked the voltage at the fuses? These old glass fuses can cause some headaches. Dirty or corroded terminals, battery terminals, multiplug connectors and switches are also common suspects. Usually a joined wire nicely taped up, where the copper strands have gone green over time, contributes to this sort of thing.
Follow that feed from the battery through the main fuse, through the ignition switch, back to the fuse and then out on the orange/white wire to the coils and ignitor. Somewhere along the way you should find the culprit!

Avoid doing the coil relay mod to cure problems like this, rather cure it as far as you can otherwise its going to come back and bite you when least expected.

[Rafe]

I found a spade connector connected to a bolt securing the battery case to the chassis. Unfortunately there was no wire connected to the spade connector. Also, there seems to be some sort of junction box connected to the bottom of the airbox. Any idea what's in there?

[tom203]

I found a spade connector connected to a bolt securing the battery case to the chassis. Unfortunately there was no wire connected to the spade connector. Also, there seems to be some sort of junction box connected to the bottom of the airbox. Any idea what's in there?

On my 81 650L, the bottom of airbox has a plate which holds the ignitor and the R/R, but the "E" version is different. Can you describe (or take pic) this "junction box" more ? I can tell anything from your coil pic! The orange/white wire supplies positive power ( thru key switch and kill switch) to both coils and also to your ignitor. That crimp-on connector likely means that someone has fiddled with wiring.

[Matchless]

I found a spade connector connected to a bolt securing the battery case to the chassis. Unfortunately there was no wire connected to the spade connector. Also, there seems to be some sort of junction box connected to the bottom of the airbox. Any idea what's in there?

It would be best to post photos, then we may be able to identify what you are referring to and help you easier.

[Rafe]

Thanx guyz, looking like I have a problem with my igniter.

[Rafe]

I replaced my igniter box/cdi and now I have 12V+ on my coils but still no spark. I am measuring 12V+ on both the positive and negative connections on the coils. Is that normal or did I hook it up wrong?