Headlight quit because of starter button?

We'll start with the basics.

85 xj700
stock fuse panel but it is blade type (behind the light cluster)
battery is good
regulator is good
alternator is good

I feel for you guys that have the "old school" glass fuses. I was really surprised to tear into this one and find automotive style plastic blade fuses in it standard.

So here's the story. I get out of work and go for a ride on the way home. It's amazing how a 5 minute drive can take 3 hours when you make a "wrong" turn and head out of town. Bike runs fine the entire way, even when I get on a back country road and crack the throttle pretty hard. A buddy of mine came along on his bike and we stopped for dinner at a place next to his apartment. I go to start the bike after dinner and the headlight is not coming on, even after starting the engine. It did work earlier because we stopped for dinner around 8:30 and it was getting dark.

In the past, the headlight comes on when the key is turned. I think this is different than previous years. But...when you start the engine, the headlight and speedo/tach lights shut off until you release the starter button. I didn't think about this until a few hours later. So engine is running and no headlight. Shut it off, pull the headlight (Thanks Yamaha for making a toolkit that actually is useful) and bulb looks funny. Ok, replace bulb...no change. Start to meter out the circuit (without the wiring diagram since my repair manual is at home) and I'm not getting voltages where I think I should.

Long drawn out story short, I pulled almost the entire front-end electrical system apart, including the fuse box, headlight and everything in between to find out it's the STARTER BUTTON!? After finding the wiring diagram online, and starting to trace it out, I remembered about the headlight cutting out when the button is pressed. I fiddle with it and get some glimmer of hope. A little wd-40 in there and the light snaps on! Not bad for working in the middle of a parking lot with a bare bones set of tools. I just wish it hadn't taken 4 hours to figure that out.

Now, here's the question. Has anyone else had this problem? Is there a typical mod for this bike that will fix this? I thought about just cutting the two wires and soldering a switch in place, just in case this happens again.

Also, what does everyone use to clean electrical connections? I have heard that wd-40 isn't the best for that kind of application. Is was just what we had at the time.

 

WD-40 works fine but won't take off a lot of corrosion. you really need to get in there and polish the pins and contacts with a wire brush after spraying them. A really small round wire brush for a Dremel works pretty well to get in between the male pins in a connector but there isn't much you can do about the female pins except to spray them and push the connector on and take if off several times to try and polish up the contact points.

 

Most metric bikes run the headlight thru the switch, which in my opinion is a poor setup. The switches get coroded or wear out eventually. Your best bet is to wire the headlight directly from the battery using a relay to run it. That way the juice will not have to run thru the switch.
Wire the relay so it is activated by the headlight switch to turn on the lights. You will need two relays, one for the low beam and one for the high beam.
If you light switch is starting to melt, replace it. If not, you can clean the contacts a little with sand paper and apply a little die-electric grease to it to keep it making better contact. PD

 

I just had this problem on my bike. And it turned out to be the same problem that you had. Thank your for the post it saved me a lot of time and heart ache.

 

So, if you're having this problem, and I am, how do you eliminate the starter switch as the cause? I try to bypass the headlight relay to eliminate that and I get smoke! at the wires running along the spine of the bike, haven't figured out which wire that was yet. No idea what happened to the lights.

I have 12V at the red/yellow wire going into the relay. If I unplug a couple things in the headlight bucket I can even get 12V at the wires going to the bulb, but light still won't come on(bulb's fine, brand new) with everything plugged in I only have 4V at the bulb. I posted about this already, not a lot of response. Likely culprits are the starter switch and headlight relay, neither of which I can eliminate, because nothing I do gets the lights to turn on.

Edit: well I got the lights working, no idea how, if I'm honest. At one point I completely rewired the fuses, because I cut the fuse box out when I got tired of blowing fuses tracking down problem, when I connected it all together again the lights started working all the sudden.