Lights on ...engine dies?

[AndyDenmark]

Hi all:)
I have an electrical problem on my 54 Golden Flash. I have recently had a Thorspark electronic ignition fitted as the magneto packed up and I wanted to get some use out of it before winter but am not sure if the problem is related to that. The bike seems to tick over fine without the lights on but as soon as the lights are turned on she dies. Any pointers would be greatly appreciated.

Many Thanks

Andy

[warmshed]

Sounds like your battery voltage is dropping too far for the electronic ignition to work properly.  Best bet is to get a meter across the battery terminals and note the voltage when you have the engine running and turn on the lights. Might be that the dynamo is not functioning correctly or the battery has very little capacity due to a fault or age.   Does  the bike run well at high revs?  Dave.

[a10 gf]

Agree with warmshed, or done some 'interesting' wiring?

[AndyDenmark]

Hi again

Thanks for the replies. The battery was new very recently and the bike runs well at high revs with good lighting. It will start and tick over fine without the lights but as soon as I turn the lights on she dies.

Andy

[a10 gf]

Try the suggested volt measurement (and tell us what shows up).

[AndyDenmark]

Will do tomorrow when I can get hold of a voltmeter :)

[warmshed]

Is it the 6 volt or 12 volt ignition? If 12 volts some regulators need a good number of revs to satisfy demand. If nothing has changed the it does sound like the battery is low, just need to look to see if the output from the dynamo gets up toward the required  7 or 14 volts (for 6 and 12 volts systems respectively). If so the battery is suspect though check battery and earth connections.  Dave.

[AndyDenmark]

Thanks again

It is a 6v system :)

[AndyDenmark]

I have a horrible feeling the dynamo is on the way out

[morris]

When I wanted to convert the SA to electronic I first wanted to stay on 6v to, but Paul Goff strongly advised against it. He said it was possible but would be troublesome certainly when driving with the lights on
What bulbs are you running? You could maybe try a led rear/stop light conversion and avoid using the headlight but use the pilot light when driving during the day. Check out Paul Goff's website, he has a lot of interesting stuff;

http://www.norbsa02.freeuk.com/GoffyDaytimeLights.htm

I noticed that even on 12V the charging system only just copes with electronic ignition

[warmshed]

Until the revs rise and the voltage rises above 6 volts, the battery has to supply the current. with the headlight on this can be too much for a small A/H battery so the voltage drops.  You dont say if your bike used to work ok with the setup you have and this is a fault that has just occurred. 

With a dynamo and a 12 volt regulator the setup is even more critical as you need higher revs before the dynamo matched the battery voltage and starts to charge, though often people going this route get a larger A/H battery and the problem might not arise.

Maybe Thorspark can let us know what terminal voltage (pun) kills the spark.

Best of luck with the testing tomorrow,  a voltmeter is a handy thing and quite cheap ones can be surprisingly good, might be worth sourcing one to keep.

[morris]

Warmshed also has a point there.
I fitted a belt drive for the dynamo and that certainly is a worthwhile investment. It makes the dynamo spin 20% faster, so charging will cut in sooner.

[AndyDenmark]

Hi all
The bike is a recent purchase so some of the history is unknown but I will try and answer as best I can. The point about just running on pilot light is a good one but unfortunately headlights are a daytime requirement in Denmark where I live. A voltmeter is a good investment and I will get one today as I am slowly building up the required tool kit. I got her back from having the ignition fitted about a week ago and have not had any problems until last night when I parked her outside the garage to open the door and she died. I will check all the connections this morning and see if I can find anything amiss and also check for voltage drop across the battery terminals when I turn the lights on. The dynamo is about tbe only thing not changed so it would be no surprise if that is buggered :)

[Greybeard]

The dynamo is about tbe only thing not changed so it would be no surprise if that is buggered :)

Hmm, 'Buggered'; is that a Danish word for not quite up to par? 

[AndyDenmark]

It is a word I imported to Denmark :). I have got a multimeter and got the following results:

Voltage on battery with bike not running 5.9v

Voltage on battery at tickover 5.9v

Voltage at battery increases with an increase of revs

Voltage drops by a volt or so when I turn the lights on.

On tickover lights are dim and sometimes bike dies. It starts first time every time and ticks over fine without lights and runs fine in use with lights on. I have a feeling that the dynamo is not quite producing enough " juice ". I have looked at one of these belt drive kits to increase the dynamo output in the hope that this will be a cheaper fix than replacing the dynamo at this stage but any suggestions as to other possible causes are of course more than welcome.

All the best

Andy