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'87 K100RS Intermittent Headlight - installing a relay

wavery

No Time to Hate
When I turn my headlight on on my '87 K100RS, sometimes it works, sometimes it doesn't. When it doesn't, the high beam indicator lights up (with no actual high beam coming from the headlight).

I understand headlight problems are common with these bikes, and reading through the forums the three things I see to do are: (1) check the ground; (2) clean the switch; and (3) install a relay a from Eastern Beaver. It sounds like No. 3 should be done regardless.

So I'm a new to working on bikes in any form (or anything with a motor for that matter). While I aspire to be more, I would call myself a two-wrencher (out of five)...I can handle most of the routine maintenance. Is installing a relay relatively simple? From what I can tell, removing the tank is the most difficult task, but I don't see what 'installing the relay' actually entails once I access the wiring.

I only recently bought this bike, after going far too long without one and I don't relish the thought of it sitting in pieces in my garage (nope, no winter hibernation for this bike). I have come to the conclusion that what I really need is a second bike so I'm not haunted by these weighty decisions (DIY or let a pro do it). Would someone please explain this to my wife?
 
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Installing a relay is a good idea and you should plan to do it. BUT, that won't cure your problem until you get the lights in OEM configuration to work correctly, except by perchance lucky accident.

You probably have a dirty starter creating a poor ground for the load shed relay. To correct this you need to remove and clean the starter. Tedious, but not difficult.

Even with a relay setup the light won't work correctly if:

a. the bulb isn't properly grounded
b. the signal to the relay is turned off by the ungrounded load shed relay
c. you have a bad high/low beam selector switch
d. etc.

Installing the relay kit is simple. Connect the ground wire, connect the fused lead to the battery, connect the relay coil signal wires per instructions (probably plug in to old headlight plug) and connect relay connector to the H4 light bulb.
 
I was going to throw out that you might want to check the switchgear wiring as well, the zip ties securing them to the frame rails and such can rub through the jacket and interior wiring over time causing all kinds of funkiness (technical term ;)). This sometimes happens with the wiring coming up the right frame rail where your right knee would be.
 
When Paul said the stater probably needs cleaning, he means the inside of the starter. The commutator gets covered in carbon brush dust and doesn't provide a good ground path.

You MIGHT be able to confirm this, if you can get the lights to not work when the motor is not running, by putting the bike in 5th gear and pushing it backwards. If the lights come back on, the starter is probably the problem.



:dance:dance:dance
 
Will,

In the future, please include the year and model of the bike IN THE TITLE of the thread so that down the road others can more easily search for similar problems on similar bikes.


Thanks.




:dance:dance:dance
 
When Paul said the stater probably needs cleaning, he means the inside of the starter. The commutator gets covered in carbon brush dust and doesn't provide a good ground path.

You MIGHT be able to confirm this, if you can get the lights to not work when the motor is not running, by putting the bike in 5th gear and pushing it backwards. If the lights come back on, the starter is probably the problem.

Thanks all for the input.

With the headlight out and the motor not running, I tried to get it into 5th gear but couldn't, so I started it up just to get it into 5th. The headlight came on as soon as I got it into 2nd gear. Is that indicative of a starter problem? Or anything else?

Thanks again!
 
When Paul said the stater probably needs cleaning, he means the inside of the starter. The commutator gets covered in carbon brush dust and doesn't provide a good ground path.

You MIGHT be able to confirm this, if you can get the lights to not work when the motor is not running, by putting the bike in 5th gear and pushing it backwards. If the lights come back on, the starter is probably the problem.

I wasn't able to confirm a starter problem as Lee described, but from what I've read, it sounds like cleaning the starter is in order regardless. So far I've found these DIY write-ups on how to do it:

http://www.ibmwr.org/ktech/starter-cleaning/starter-cleaning.shtml

http://skylands.ibmwr.org/tom/tech/starter.html

Any other suggestions or tips?

Thanks all!
 
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Add a Relay

I can vouch for the value of a relay, and if you a going to replace the headlight switch this is a very good time to do it. The relay allows the current path to avoid relying on the relatively puny switch contacts to activate the light. One reason switches go bad is current overload from the start-up demand. The relay eliminates this as an issue. I added the Eastern Beaver relay set-up when I replaced my headlight switch unit and it also increased the luminosity of the light because of more efficient current transfer.
 
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