1980 Yamaha xs400SG Headlamp Will Not Come On

[jlearning1]

Hello my friends. It me again. First of all I would like to thank everyone on this forum for their prompt and generious help. My 1980 Yamaha 400SG Headlamp will not come on when I turn the switch on. I have swapped headlight bulbs and it still will not come on. Heres the tricky part. When I try to kick start it, the headlamp comes on, but I cannot control the on and off from the main switch. I have to turn the key off, and the headlamp goes off. I kick start it again, and the headlamp comes on. Does anyone have any suggestions why this is happening? And 1 more question. Does the guages (tach and speedometer) suppose to illuminate when the key is on and the lights are on?

Thanks Again

 

[drewpy]

I think the US front lamps are lit via a relay direct from the alternator. so kicking it with produce a voltage. check the battery for amps and that relay!

gauges may come on when the headlamp comes on.

 

[HoughMade]

They are not lit directly from the alternator, but there is a circuit that does not let them come on until the there is an attempt to start it. This is to provide a little extra juice for the first spark when starting. The light will then stay on, bike running or not, until the kill switch is turned off or the ignition switch is turned off.

In other words, that's the way it is supposed to work.

 

[jlearning1]

So from this I am understanding that unless the bike is running the headlamp will not come on even when the key is turned to on and the kill switch is turned to the on position. When I turn my key to on and the kill switch to on the headlamps does not come on. My bike is not running at this time. I do have a good charge battery. Do the bike have to be running for the headlamp to come on?

Thanks

 

[HoughMade]

No matter what position the switches are in, the light will not com on until you either kick it or thumb the starter button. If it fails to start, the light will stay on. You can not turn the light on just to turn the light on. You have to at least attempt a start for it to come on.

 

[bcbobbers]

+1 houghmade, yes that is the way they are supposed to work, if you kill the bike with the kill switch it will stay on until you turn the key to off, the kill switch has nothing to do with it, but the light is not supposed to turn on until the bike was at least attempted to start.

 

[jlearning1]

Thanks My Friends. I will give it a try and sees what happens. I will post back and let you all know

Thanks Again

 

[drewpy]

so its like a latching relay, so once energised it completes a circuit, when off via the switch (prob red/white ignition) the relay unlatches?

 

[hmusket]

^Yes, in essence.

 

[Ebola Monkey]

By 1980 they realized the charging system was shit, and thought maybe it would help to keep the amp draw down until the engine was running.

You can get around it by eliminating the relay (lower right side of bike), but it will just make it more likely to not start via the starter.

 

[HoughMade]

Mine has it in '79. Also, there are those who believe that the electronic ignition is what causes problems for the charging system and that points bikes in good repair have less electrical issues.

 

[SilverTalon]

Yeah I have the same issue. On mine the headlight and the gauge lights will not turn on when I start the bike, I end up having to wait 1-10 minutes, or while I'm running and they will suddenly turn on.

I just replaced my headlight with a lower wattage and that had no effect.

 

[HoughMade]

Try wiggling the wires going in an out of the fuse box. Sounds like a loose connection, not a charging issue. I rebuilt the whole fuse box (couple of hours tops) and the electrical system has been reliable since.

 

[SilverTalon]

Try wiggling the wires going in an out of the fuse box. Sounds like a loose connection, not a charging issue. I rebuilt the whole fuse box (couple of hours tops) and the electrical system has been reliable since.

Yeah I was looking at replacing the fuse box with something newer. Here is what my current one looks like.

 

[Ebola Monkey]

Go to radio shack, and buy their glass fuse block. It's around $2 and fits inside of the stock fuse box.

A little cutting, and soldering, and you'll have something resembling stock. I obviously reused the sticker.

 

[SilverTalon]

Go to radio shack, and buy their glass fuse block. It's around $2 and fits inside of the stock fuse box.

A little cutting, and soldering, and you'll have something resembling stock. I obviously reused the sticker.

Correct me if I'm wrong, and I hope I am, but by the looks of it am I supposed to have four fuses, not just two?

 

[drewpy]

Correct me if I'm wrong, and I hope I am, but by the looks of it am I supposed to have four fuses, not just two?

your wrong, stand corrected

yep 4 fuses 3 x 10amp 1 x 20 amp

 

[SilverTalon]

your wrong, stand corrected

yep 4 fuses 3 x 10amp 1 x 20 amp

Dare I ask for your thought on how my bike is running with just two fuses? That has me worried now (although, it means another project for me )

 

[drewpy]

just doubled up on the feeds probably, or didn't bother with fuses at all!

 

[Ebola Monkey]

It looks like they hardwired the ignition, ans signal fuses if memory serves.