Dr Big

Full Version: No spark fault finding
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My bike has become progressively harder to start over the last few weeks. Once started it seems to run 100%. Now it has got to the point that today it refuses to fire up at all. I haven't had time to check anything else yet but I can confirm there is no spark.

So what is the checklist, in the most logical order, that I need to run through, to fault find this?

Thanks
Will the starter still spin the engine? I’m assuming that it will.

First thing to check is the backside of the ignition switch. You’re looking for wires that are loose or broken from the solder connections.

Next test the right side “kill” switch on the handlebars.

Then neutral switch, clutch interlock switch and the side stand switch.

In general do everything easiest to get your hands on first. Since the bike has two plugs and two ignition coils, the chances that the problem is under the tank is rare.

Have you had the right side case off the engine recently? The next check is for pinched or broken wires as they exit that case.
Thanks Ray. Yes starter spins well and the battery is good. I have previously disabled the side stand switch and as far as I recall the kill switch disables the starter, not the ignition?

This is my plan of action; corrections or suggestions welcome:

1. Check power supply to CDI. Black/Yellow wire from ignition switch. If no power check underside of ignition switch for loose connections.
2. Unlikely to be ignition coils in this case but will check in any case. Primary 0-1 ohm and secondary 10-17 K ohms
3. Check pick up coil. Green and orange wires. 175-265 ohms
4. Check charging coils. 3 yellow wires. 0.5 - 0.8 ohms
5. Check exciter coil. Black/red and red/black wires. 230 - 355 ohms

If all those check out I suppose I should begin to suspect the CDI?

When it first began the hard starting problems I did check spark. There was spark and so I turned my attention to the carbs. Stripped them but they were spotless and there was no change once they were reinstalled. In hind sight the spark did seem very weak. So I'm pretty sure I've had a weak spark condition which has been getting progressively worse over a few weeks and now total failure.
If you go through Ladder`s check list and then your own you should find it.
CDI problems are usually very rare on a Big.
My guess would be a pick-up coil  as I`ve known a few of those to expire
Ok so I don't seem to have power to the CDI. I can't see any loose connections at the ignition switch. I just want to confirm; is the yellow/black wire the power supply to the CDI from the ignition switch?
Posted the thread number on ADV to the color wiring diagram.

But, yes, the yellow/black wire goes from the ign switch to the CDI. It ALSO goes to the right handlebar kill switch so your problem may lurk there also.

Trying to post the wiring diagram here but not having success so far....wait....I think I've done it. At least it works for me. Hopefully everyone can see it - if not - let me know

SR41 color wiring diagram
We did  have the wiring diagrams on here and in English but they seem to have disappeared.
There is a mistake in the wiring diagram that Ladder posted....
The wire from the decomp lever to the decomp relay should be black and not blue.
Thanks, I do already have the wiring diagram. And yes the black and yellow wire runs from the ignition and the kill switch to the CDI but I'm beginning to wander if that actually is a 12V+ feed. I'm trying to understand from the wiring diagram what is actually happening in the ignition switch. But it looks like both the ignition switch and kill switch complete a circuit with the black and white wire coming from the CDI. I'm guessing that somehow grounds it or shuts it down. Hopefully someone who understands wiring diagrams better than me can explain it.
The way I'm seeing it is that the yellow wire is grounded (earthed) when ignition is off. This kills power to the CDI.

The CDI is powered by the Red/Black and Black/Red wires coming off the stator

The CDI it triggered by the solid Yellow and solid Green wires coming from the ignition sensor on the stator.

The side stand switch is also in the mix. A white wire comes off the CDI and then turns to green at the switch pigtail. It goes to ground with the switch is closed (SS down).

You said you disabled the SS switch. You might retrace your steps here and make certain your method of removing it is not faulty or has somehow found a way to ground.
That is exactly the way I understand it too. Thanks for confirming that. I expected to see a 12V feed from the ignition to the CDI so when I saw that yellow/black wire I jumped to a conclusion without carefully looking at the rest of the circuit.

Anyway back to the drawing board now in the search for the issue.
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