bike dies when headlight turned on!?

After balancing the carbs at home to an acceptably rough idle, things were going well, I then turned on the headlight and the bike idle went really rough and died. I turned the light off and re-started the bike and things were fine, turned on the headlight again and had to try hard to get it to maintain an idle!

This is new to me! Could it be the coils? Or the charging circuit? I am pretty handy around mechanical items, but electrics are a mystery to me!?

Any ideas or people with previous experience would be a huge help!

cheers

 

The headlight should "come on" automatically when the bike starts, so by what method are you turning it "on" after the bike is started? Has someone added an accessory on-off switch to the lighting circuit?

In any cas, it sounds like the battery is low on voltage (either it's old and worn out, or the charging system is not fully charging the battery), and the additional voltage draw by the headlights doesn't leave enough power to run the ignition system.

Also, tell us what kind of bike you have, that may help with further diagnosis.......

 

I should have included the bike, it is an XJ650 RJ sports style, ie: non-cruiser. It is an Australian model so I am assuming the wiring requirements might be a bit different.

I had another go at the bike, after starting it up again, she has an even more eratic idle now, regardless of whether the headlight is on or off, and she has started backfiring on one or more cylinders.

This convinces me it has to be an electrical issue. Does anyone know of a website or link in this forum with instructions on how to test the electricals with a tester? coils, battery, silicon rectifier, ignition module?

cheers

 

These links should help
http://xjbikes.com/Forums/viewtopic/p=2 ... tml#233957
http://xjbikes.com/Forums/viewtopic/t=27543.html both by Chacal.
Unfortunately I'm not good with electrickery either.

 

The first clue is the statement "acceptably rough idle".
There is no such thing..A proper bench or vac sync should provide
a perfectly rideable condition. Maybe not to the fine tuned
perfection of most of the riders on this site, but fine for the average
rider.
If you have a rough enough idle to begin with and additional load, (i.e. headlight draw) then there is not a balance of power in the cyl to keep up with the demands of the ignition circuit and it will die.
In order for a motor's electrical system to take over from batt
to gen, the motor must be running in a consistant manner.
The whole system relies on infirmation from the pick-up
coils telling the TCI that the batt is no longer needed to run the power
system and the generator has in fact taken over the electrical demands
of the bike.
In the old days you had points instead of pick-up coils. If you didn't
stay on top of the gap then the timing was off and the bike ran like
crap. With all the complextion of modern electonics, the "brains" don't
need much to deside to shut down if the information is inconsistant.