1974 Commando 850 no spark

Ekvin · Aug 7, 2015

Trying to get a 74 Commando 850 started. It had bad gas in it and gummed up the carbs. Cleaned up the carbs and it was running beautifully and turn over and idle on first kick. The next day however it won't fire up and there doesn't seem to be any spark. Thinking it may be the coil, but not sure how to check it?

Rohan · Aug 7, 2015

Do the lights come on, bright and strong ?

Got power to the coils. ?
Still points, or leccy ignition. ??

Old unused wiring can get crusty in the connectors, may be a matter of tracing through the wires and ensuring good clean connectors.
Fuse got good connections too, any corrosion can make for feeble connection.

Ekvin · Aug 9, 2015

Lights come on strong. battery is good. I believe it has a Boyer electronic ignition, going to try and bypass it today and see if that works. Used BPR7ES plugs as couldn't find a regular BP7ES, it was running with those plugs but wouldn't start the next day. Will also try to track down a non resistive plug in case that is an issue.

74ok · Aug 9, 2015

you haven't said, did you check for spark? i'm assuming fuel flow (and choke use) hasn't changed and is ok

concours · Aug 9, 2015

"Doesn't SEEM to have any spark", you've checked, yes? If test reveals no spark, jumper out the kill switch, re-test.

nberg · Aug 9, 2015

If no spark at plugs, suggest also bypassing ignition switch.

maylar · Aug 10, 2015

concours said:
"Doesn't SEEM to have any spark", you've checked, yes? If test reveals no spark, jumper out the kill switch, re-test.

Push the kill button a few times and let it snap back. They get intermittent.

Ekvin · Aug 10, 2015

Fuel and choke use hasn't changed, all seems fine there and confirmed that there is no spark. Power running to the Boyer Ignition but nothing after. Looks like it may be the problem, will likely be buying a new one. Thanks for the help guys.
Cheers,
Kevin

74ok · Aug 10, 2015

someone else will have to chime in how to test & confirm a dud boyer, i'm not familiar with it,

best to confirm issues prior to going to something else,

right now you have no spark and a suspect boyer

L.A.B. · Aug 10, 2015

84ok said:
someone else will have to chime in how to test & confirm a dud boyer, i'm not familiar with it,

http://www.tioc.org/boyer/boyertestnewweb.htm

http://www.boyerbransden.com/faultfinding.html

Towner · Aug 10, 2015

Hi,

the Boyer like to have broken wires under the little tie at the timing plate. It is a special Commando issue caused by the vibration between engine and frame due to the isolastics. You can't see it, it's inside the cable.

Ralf

Ekvin · Aug 28, 2015

Thought I would update the post as been away for work. My friend ended up ordering a new Boyer black box but the issue turned out to be a broken wire at the coil.
All is good now, thats one more Norton back on the road after 15 years in a shed.
Thanks for the help everyone!
Ekvin

Nater_Potater · Aug 28, 2015

Thanks for the follow-up. It's always nice to see when something goes right.

ewgoforth · Aug 28, 2015

With a Boyer check for broken pickup plate wires: Disconnect the points wires from the points plate and touch them together. If you get a spark, but not when you kick the bike over, breakage in the pickup wires is likely. You can test for broken points wires in a similar way by jumpering the wires going into the black box.

1974 Commando 850 no spark

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