The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Magista on 16.03. 2023 23:41

Title: Smoking Wire
Post by: Magista on 16.03. 2023 23:41

When returning from a short ride I noticed smoke coming from this wire which I assume is for the magneto cut out switch. You can see the discoloration.

I assume this is a short I'll have to track down. If anyone knows of the top of their head feel free to chime in.

Title: Re: Smoking Wire
Post by: Colsbeeza on 17.03. 2023 03:41

Hi Magenta,
Yes it is the magneto cutout earth wire, connected to your cutout button on handlebars. Unusual to short out - I am sure Cheeserbeeser (Andrew) will have an opinion. Another possibility is fuel leakage from the LHS tap caught alight, but then why did it go out?
Col

Title: Re: Smoking Wire
Post by: CheeserBeezer on 17.03. 2023 08:16

Quote from: Colsbeeza on 17.03. 2023 03:41

Hi Magenta,
Yes it is the magneto cutout earth wire, connected to your cutout button on handlebars. Unusual to short out - I am sure Cheeserbeeser (Andrew) will have an opinion. Another possibility is fuel leakage from the LHS tap caught alight, but then why did it go out?
Col

Colsbeeza is correct in that it is difficult to see how current could be draining down this wire without, at the same time, the bike stopping. The wire is connected to the primary windings via the brush in the magneto endcap so. if current is draining down the wire sufficient to heat the wire the primary circuit must be shorted out and the bike would stop. Awaiting your further investigations with interest? Is the wire actually hot to touch?

Title: Re: Smoking Wire
Post by: muskrat on 17.03. 2023 08:47

G'day Magista.
In case it needs topping up. *sarcastic* *whistle*
Cheers

Title: Re: Smoking Wire
Post by: Magista on 17.03. 2023 15:47

Thanks for the feedback everyone. As always, it's appreciated.

The other possibility is I saw the smoke and assumed it was from the cut-out wire when in reality it was just a bit of oil burning off the exhaust...which honestly sounds more likely and I'm an idiot.  *doh* The discoloration may be just grime and I'm imagining the whole thing.

I'll fire the bike up again this afternoon, see what happens and report back.

Title: Re: Smoking Wire
Post by: Triton Thrasher on 17.03. 2023 16:57

The magneto’s low tension current can’t burn a wire that thick.

Title: Re: Smoking Wire
Post by: Magista on 19.03. 2023 16:55

File this one under “Doh!”

It was just some oil burning off the exhaust.

Thanks everyone.