Paging the bike electricians

Right, I've recently acquired a lovely old 1981 Yamaha XS650 Special.
It's a US import (quite common over here in the UK). It's a 1981 model
with cast wheels.

Being a US model, it also has the headlight permanently wired into the
ignition. When you hit the starter button, the headlight goes out,
presumably to alleviate the load on the battery while cranking the
engine.

Recently, the headlight has decided to stay unlit when you turn the
ignition on. However, the first rotation of the engine brings it up.

If you hit the kill switch to cut the engine, the headlight stays on
(and then goes out if you press the starter button, before re-lghting
when the engine fires, as it should).

If you turn the engine off with the key, and then turn it on again, the
light stays out until the engine turns over.

Also, under the seat is a small grey box bearing the legend Reserve
Lighting Device. It's made by Koito and carries a serial number
337-11720. Googling on this brings no hits. I'm assuming it has
something to do with the headlight, because it doesn't exist on old
UK-spec models.

Questions:

1. Why would the headlight stay out until the engine starts revolving?

2. Would this Koito thingy have anything to do with it?

3. As the bike's charging perfectly and running A-OK, should I just
shrug and put it down to the Bad Yamaha Pixies?

 

It's because the donor bike (which I'm currently stripping down) turned
on its headlight with the ignition switch, engine running or not. But
yes, I'll ignore it. I'm not worried - just curious.

 

Might be the start switch which has push-to-break contacts for the main
lighting circuit.

The following info is for a Yamaha triple; it might or might not apply to
the XS650:

"The triples came with a reserve lighting unit that acts as a fail safe
device. If you are riding with the low beam on and the bulb burns out or
there is a faulty connection, the reserve lighting unit automatically
switches to the high beam and illuminates the indicator light that is
marked "headlight". The same thing will happen if the high beam goes out,
it automaticly switches to the low beam. The "headlight" indicator light is
there to tell you that there is a problem somewhere in the lighting
system."

I have a similar problem with my '95 XV250. In my case, it's the start
button not always making good contact with the lighting circuit after it
starts. I simply push in the other end of the start switch (not the
protruding part, but the part that's flush with the housing IYSWIM) and the
light comes back on. Dirty contacts is my guess and someday I'll take the
switch apart and clean it.

 

OK, I guess there is a relay somewhere in the ignition circuit that is
supposed to switch 'on' as soon as the ignition is turned on. Pressing
the starter button interrupts the current to the relay so it turns into
its 'off' position, thus switching the headlights off as long as you
press the button. You let go, current flows through the relay again, it
switches and the headlight comes on again.

That's roughly when it starts charging, right?

My guess is that either the relay is a bit dirty and the current
flowing through it is not strong enough to switch it on, or the battery
voltage is too low to get it to switch.

Get your multimeter out, turn on the ignition and check the voltage at
the battery. If it looks alright, give the grey box a friendly tap and
see if the headlight comes on.

 

Right! I hadn't thought of that.

OK, so that's what the gizmo does. Makes sense.

Thanks. I think you've hit the nail on the head.

 

Hello,

If you take a look at the wiring diagram of this XS model you can see that
the headlight is switched on by the "Headlight relay". When the engine is
off the relay is in its standard position. In this position it is possible
to turn on the starter motor. When the engine runs the relay is activated by
the yellow wire coming directly from the A.C. generator. The headlight is
turned on but it is not possible anymore to activate the starter motor which
is quit logical. When you cut off the engine with the kill switch the
headlight will remain on. After you turn off the ignition the headlight will
turn off.
The function of the Reserve lighting device has been described correctly by
"doc":

"The triples came with a reserve lighting unit that acts as a fail safe
device. If you are riding with the low beam on and the bulb burns out or
there is a faulty connection, the reserve lighting unit automatically
switches to the high beam and illuminates the indicator light that is marked
"headlight". The same thing will happen if the high beam goes out, it
automaticly switches to the low beam. The "headlight" indicator light is
there to tell you that there is a problem somewhere in the lighting
system."

In addition: the high beam is switched on in series with a resitor so you
will not dazzle any oncoming traffic.

Greetings,

Haro van Santbrink
[Yamaha XS650SE 1983]
[Ducati Pantah 600TL 1983]
[www.xs650.nl (Sorry, only in Dutch....)]

 

Perfect. Thanks.

 

By the way, Older Gentleman, buy a good workshop manual like the one by
Haynes (ISBN 1 85010 921 4). Cost a few pounds but it is worth every penny.

Greetings from Holland

Haro

 

I have one, actually.

 

Thus spake Timo Geusch unto the assembled multitudes:

Sounds a bit like the rear screen heater in my car which is controlled by a
relay. The heater relay will only engage when the engine is running. I
also immediately thought of a push-to-break contact at the starter button.

 

(The Older Gentleman) wrote in

I never liked Haynes. I always went to the dealer and got the factory
manuals. I have never been been disappointed in the factory manuals. Sure
they cost more than the Haynes, but you do get what you pay for.

Pierce

 

Which is why you'll commonly find Haynes manuals referred to as Haynes
BoL (Book of Lies) around here...

 

Agree 100%.

Haynes are pretty good, but a factory manual is worth the extra, if
you're planning any serious work.

 

I also like to have a parts list to hand. The exploded
diagrams are handy for putting the "pingfuckits" back in the
right order....

 

(Frinton Boy) wrote in

Mine usually go "sproing..tink,tick,tink...shit!"

pierce

 

(The Older Gentleman) wrote in

The Concours factory manual is thorough, but the coloured wiring diagram in
the Haynes manual would be nice.