Electrical Gremlin

[jowek70]

Hello forum,

I have a 1981 xs650 that has a somewhat modified wiring harness (stock gauges removed in place of a digital set-up by PO) and about a week ago it developed an odd problem. It has original fuse box (4 glass tubes) and when you turn the key on everything works great but as soon as you put the killswitch to RUN it pops the headlight fuse. I looked at all the wiring and tidied up the wiring in the headlight bucket hoping i'd find a loose/worn connection to no avail. I read around and removed the self cancelling signal unit and the reserve lighting source (tying the needed wires together) but that didn't help either. Most recently I disassembled the killswitch and everything inside is nice and tidy and seems to function as it should.
Could there be something under the gas tank that is grounding out? That's the last place I have to look yet but I removed the tank yesterday and nothing was obviously wrong.
Any help is appreciated.

 

[xjwmx]

Do you have an ohmmeter? I would put one probe on the hot side of the kill switch and the other on the fuse and keep checking back from the switch going toward the fuse until you find how they're connected and what the problem is. If the wiring is really the chopped up pits and everything is relatively stock, a new harness isn't too high maybe.

 

[jowek70]

Thanks for the advice, I do have a multimeter.
The harness is only modified in the headlight bucket, the rest is stock outside of what I've done to it since.
I'll admit there is a lot going on in the headlight bucket but whoever did the mods for the digital gauge seems like they did a decent job.
I have had the gas tank off recently and I think something might have happened when I reinstalled it or there is an issue in the handlebars, I think I read that they act as a ground?

 

[xjwmx]

Right, the handlebars are ground, I think through the turn signal switch since they;re rubber mounted. I have an '81 too. Do you have a circuit diagram? There's a color one that's easy to follow. Are you sure it's the headlight fuse? Are you going by the wire color? Headlight circuit shouldn't even have any power until the engine starts running.

 

[650Skull]

Post #7
http://www.xs650.com/threads/some-wiring-diagrams.61/

 

[xjwmx]

Something that occurred to me, the digital tach is probably connected to one of the coil primary wires. If that branch of the tach circuit was shorted to ground somewhere it would blow some fuse when you flipped the kill switch on the handlebar. You might be able to ride if you just unplug the tach...

 

[gggGary]

Well for sure remove gas tank and check around the front mounting "cups", gets pretty crowded round there with a harness wire group passing to the headlight bucket on both sides.

 

[jowek70]

Right, the handlebars are ground, I think through the turn signal switch since they;re rubber mounted. I have an '81 too. Do you have a circuit diagram? There's a color one that's easy to follow. Are you sure it's the headlight fuse? Are you going by the wire color? Headlight circuit shouldn't even have any power until the engine starts running.

Red/yellow in to fuse and red/yellow out of fuse in box. Says HEADLIGHT or HEAD, IIRC.

 

[jowek70]

Post #7
http://www.xs650.com/threads/some-wiring-diagrams.61/

Thank you

 

[jowek70]

Something that occurred to me, the digital tach is probably connected to one of the coil primary wires. If that branch of the tach circuit was shorted to ground somewhere it would blow some fuse when you flipped the kill switch on the handlebar. You might be able to ride if you just unplug the tach...

I will see if that helps.

 

[jowek70]

Well for sure remove gas tank and check around the front mounting "cups", gets pretty crowded round there with a harness wire group passing to the headlight bucket on both sides.

Definitely, on my list to check.

 

[jowek70]

Ok had a few hours spent on it and didn't find anything damaged/frayed/grounded anywhere on the bike but I did find that if I unplug the relay (part #2F0-81950-50-00) that my headlight fuse does not pop but I have no starter button functionality.
Is there a way to check this relay or if I replace it will it fix my issue?
The bike was starting/idling fine up until the electrical issue showed up so i'm wondering if these ancient electrical components might have burned out or something while I was tuning the carbs in?

 

[Bushyeyed1]

I am assuming your attempting the start with the light switch off so we can rule that out. If it was me I would check two things. The actual cable connected to the starter solenoid especially underneath the air box battery area. Next I’d probably pull off the headlight and inspect the rats nest of wires inside it for a short as well.

 

[gggGary]

Open that headlight shell again, double check wire color matching, I suspect a green and black are mis-connected.

 

[jowek70]

I am assuming your attempting the start with the light switch off so we can rule that out. If it was me I would check two things. The actual cable connected to the starter solenoid especially underneath the air box battery area. Next I’d probably pull off the headlight and inspect the rats nest of wires inside it for a short as well.

Just redid all the wiring in the headlight bucket so its nice and tidy now.

 

[jowek70]

Open that headlight shell again, double check wire color matching, I suspect a green and black are mis-connected.

Thanks for the info; I seem to recall several green and blacks under there, i'll have a look again.

 

[jowek70]

I am assuming your attempting the start with the light switch off so we can rule that out. If it was me I would check two things. The actual cable connected to the starter solenoid especially underneath the air box battery area. Next I’d probably pull off the headlight and inspect the rats nest of wires inside it for a short as well.

There's only hi/lo function on the light; its on as soon as the key comes on. Recently replaced the starter solenoid and both battery cables and everything in that area checked out.

 

[650Skull]

Open that headlight shell again, double check wire color matching, I suspect a green and black are mis-connected.

Just redid all the wiring in the headlight bucket so its nice and tidy now.

I think what gggGary is getting at is, Dg, (Dark green) or Ch, (chocolate), indicator wires can be mistaken for a black if slightly dirty.......The main wire from the indicators is usually black and they have to be connected to either Dg or Ch ........They, (Dg-Ch), also run into multi bullet connectors so it can be easy to get them crossed with a Black, (earth/ground).

 

[jowek70]

I think what gggGary is getting at is, Dg, (Dark green) or Ch, (chocolate), indicator wires can be mistaken for a black if slightly dirty.......The main wire from the indicators is usually black and they have to be connected to either Dg or Ch ........They, (Dg-Ch), also run into multi bullet connectors so it can be easy to get them crossed with a Black, (earth/ground).
View attachment 143989

Thanks for the photo.

 

[jowek70]

I've attached a photo of the headlight harness.
I unplugged every single wire last night and I still have the issue when I turn the kill switch to 'run'.