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Virago Headlight Problem
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So I have an 83 Virago 750. Headlight will turn on when the key is in
and on, and it stays on during starting. But as soon as the bike is
on the headlight dies. The taillight is still on, just no headlight.
I sat on it today and discovered that the light will flicker at almost
exactly 2000 RPM. More and it dies, below ~1800 and it dies. But at
2000 RPM it will flicker.
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The symptoms indicate a bad connection somewhere in the supply to the
ignition bus.
The ignition bus is not yellow, it isn't a school bus. The ignition bus is
the source of power to everything that works when the ignition key is turned
on.
There are at least two sets of contacts in the ignition switch. One set of
contacts
powers the tail light and the other set of contacts powers the ignition bus
which supplies power to the headlight, brake light, instrument lights, horn,
turn signals, etc.
Typically a red wire will come from the rectifier regulator to the battery
positive terminal and then another red wire with an inline fuse will go to
the ignition switch.
Then a wire of a different color goes back to the fuse panel to supply the
ignition bus. Suzuki always used an orange wire, your Yamaha may be different.
Suzuki always used a brown wire to go to the tail light.
You can follow out the wires from the head light fuse to the headlight
connector and also check out the grounding wire from the headlight connector.
But I suspect the problem may be in the ignition switch itself. I have had at
least three ignition switches get so hot they burned the insulation of the
wires going to them, or melted the solder attaching the wires to the switch.
Why does the headlight work, with the engine off, if the switch is defective?
The burnt contacts have high resistance, and the resistance gets even higher
when the engine is running and the voltage to the ignition bus rises from
12~volts
to 14.5 volts.
The I squared R loss across the bad contacts increases and nothing gets to
the headlight.
Another possibility is that one of the production break connectors has bad
contacts. Production breaks are connectors in the wiring harness that are
there just to make manufacturing assembly simpler. They are rarely ever
disconnected by anybody, not even a $tealer$hip mechanic.
Production breaks will be in inconvenient places, like up under the gas tank.
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What steps can I take to determine if a new starter switch is
definitely the problem? A friend mentioned that it could be a bad
regulator thus causing the light to come on only at a certain RPM. I
plan to take that off and check it out a bit. But I am on a college
student budget and can't afford to keep buying parts that don't fix
the problem. haha.
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Maybe it's time you take a course in logic and reasoning! ;-)
In this case, the most likely causes are also the cheapest to fix.
Get a new bulb. If that doesn't fix it, then you have a spare.
Check for loose or chaffed wires.
Ask one of your Professors what Ocham's Razor is!
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The starter button is rather old and doesn't stick out anymore, but I
took it apart and pushed it out with no help. I haven't really
checked the wiring out, but this doesn't seem a likely culprit as the
headlight works as long as the bike isn't running. I tried shorting a
few of the relays, to no avail.
Any suggestions?
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Check/replace the bulb first.
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Either buy a replacement starter button and spring from someplace like
PartsNMore or OldBikeBarn, or just drop $45 and get a generic control
replacement at MikesXS.com.
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Look, the Virago has a system that cuts the headlight when you press the
starter button, so as not to reduce the current getting to the starter
motor. The engine fires, you release the button, the light comes on
again.
If the headlight is working fine when the engine is not running, then it
is one of two things:
1. A bulb about to go, or a dicky connection that makes and breaks at a
critical rpm.
2. The duff starter button switch rattling in the housing and making and
breaking the contact. But if that were the case you ought to hear the
starter motor trying to engage as well, unless you have to pull in the
clutch as well before the starter spins.
The starter buttons on these old Yamahas are notorious for falling out.
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I understand the starter cut-off. Funny thing is, the light stays on
during start-up. The whole time the starter is cranking the light is
on, albeit flickering.
I have no problem buying a bulb and keeping a spare, but buying things
like regulators and starter-switch assemblies isn't overly practical
and having a spare of those doesn't help me much.
And I understand Ocham's Razor. Although I have to say Wikipedia is
far more useful than your average professor in explaining that one.
My best guess at this point is a loose wire or the regulator. The
starter cut-off doesn't seem likely as everything else functions just
fine. Its just the headlight. And the fact that it is 2000 RPM
exactly that makes the headlight flicker makes me think it is a
regulator problem, not a problem with a relay. I need to find some
time to work on it, I just haven't yet. Especially as it gets me from
A to B for the moment.
Is there a way to hard wire the light so as to make it work apart from
the starter cut-off, etc.? Hell, I wouldn't mind having to manually
turn it on after the bike is on. At this point I just need a light in
case I get caught somewhere at night and have to ride home.
Another note. When the light flickers, it seems to be somewhat
coordinated with the RPM. During startup it will flicker in time with
the motor turning over. And when it flickers around 2000 RPM it will
do so somewhat in time with the RPM. If it drops to 1900 RPM it will
flicker a bit slower. Its hard to tell this for sure as it is such a
tight range that it will actually flicker when the bike is running.
But it appears to do this.
Not sure if that changes anything.
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