Commando ignition failure.....

Hi Paul,

So just to clarify, you have boyer ignition and you have changed / checked everything except the pickup unit. If this is the case then this sounds like a classic problem. Either the wires where they connect to the pickup plate are broken or (as I have seen a few times) the wire just a little away from the pickup plate is broken. It will look ok and the connections may be good but a gentle tug will show that the wire is stretchy !

When it is cold it makes contact, when hot it does not.

I did write an article in Roadholder a while ago about using an LED fitted on the coil to diagnose boyer problems. If you cannot find it then I will dig it out.

I will be at Norton day, Commando 850MkIII with white Pantera fairing and white craven panniers. (As in my picture above).

Regards

Tony

Hi Paul

have your checked the wires from the boyer pick-up, had a failure similar to your's , ie all other electrics seemed ok

one of the ( for want of another word ) points wires had broken inside it's sleeve near where its soldered to the circuit board , looked good and intact to the naked eye,

but showed up to be broken when I tested it for continuity between pick-up and coil.

put a meter on either end and waggle the wire, happy hunting

steve

Hi Again, just found the text of the article, couple of minor changes from the original:-

Connect an LED such as www.maplin.co.uk Order Code: CJ66W across one of the coils (either will do as they are in series), do this while you know the bike is working correctly then you can easily detect if you have fitted the LED back to front, it will not light. Tape or tie wrap it to the side of the coil so it can easily be seen.

The procedure. Turn the ignition ON and the LED is OFF. Using the kickstart, gently turn the engine so it goes over TDC, the LED will comes on and stay on. I believe on later Boyers, the LED will slowly fade after a short time. Now give it a more enthusiastic prod on the kickstart, the LED will flicker off at the firing point but this is very brief. Your system is working correctly.

Turn the ignition ON and the LED is OFF. Using the kickstart, gently turn the engine so it goes over TDC the LED stays OFF. There is no power to the Boyer, or possibly the Boyer is completely dead.

Turn the ignition ON and the LED is ON. The wires to the pickup are broken or diconnected. If you wish to prove the pickup wires are working, touch the two pickup wires together and release, the LED will go on when released and go out when connected. You will also hear the spark. This LED can stay in permanently place so if the bike every fails to fire you can quickly determine if it is a problem with the Boyer or its wiring.

Hope this helps.

Tony

Previously Chris Grimmett wrote:

There is a related but rarer cause of intermittent Boyer failure. Apart from the frequently reported pickup wire problem, you can have a break inside a pickup coil. It is all related to the heat of the engine.

The symptoms are not there from the start, followed by failure when the bike gets hot, then seemingly no problem again as you begin to look at the thing and the bike cools down. Once you get going, everything heats up again, the coil goes open circuit and you come to a halt.

Been there, done that - International Rally in Vezio 1999 (or thereabouts).

Nor really relevant, but, yes Vezio was 1999, and that really was a rally worth attending!

Try the kill switch. It's a nasty little blighter and can give you no end of entertainment. Disconnect the live wire to the ignition feed and run a temparary wire from the battery, ie, hot wire it. That will eliminate all the loom feeding the ignition.

Previously paul_smith wrote:

I have an intermittent ignition failure on my â72 Roadster Commando which started about two months ago.

While riding along the ignition fails and the bike stops!

No sparks from either side â while Iâm fiddling around checking the HT leads and the coil connectors the ignition returns. I then pack up my tools and return home to try something else to fix the issue.

At the time of the failed ignition I have all the other usual electrics, horn, lights, undercurrent light etc.

So far Iâve re-soldered many connectors in the loom and especially those connecting the coils to the loom. New HT leads and HT caps, replaced both Coils with known good ones (although since both fail, this was probably a waste of time). The bike runs a solid state regulator / rectifier, one from Paul Geoff (not replaced as yet).

After todayâs failure just north of Brighton Iâve replaced the Boyer Branson black box with a used spare that came with the bike and was replaced with a new item when the previous owner completed an engine rebuild (Norman White did the actual rebuild).

So it feels like something is giving up once the bike is hot, or I have a broken wire or bad connection which is causing the loss of all sparks from time to time. If the fault would stay solid then I could diagnose and fix the issue, but as soon as the bike cools down the sparks return.

Iâve yet to run the bike with the alternative Boyer â Iâll try that at the weekend â you may see me parked up towards The Chequers Inn Doddington on Sunday â if so give me a wave.

Any other thoughts or ideas gratefully received? Thanks â Paul.

Hi Paul. I had the self same problem on a Bonneville and like you was at my wits end..I replaced just about everything and still 10 miles or so into the journey the spark would vanish only to return later. In desperation i put it into a repairer whom had it fixed in no time telling me it was a faulty earth (im sure i checked them all) but its worth a look.

Good luck. Mark 72 Commando owner.

I run a sachse electronic ignition and in the excellent instructions there is a caveat that electronic ignitions are more sensitive to intermittent losses of power than points. Removing the kill switch from the circuit seems a good idea.