Hi. I just stumbled upon this space today. It's great.

I recently bought an older (1987) K100 RS. First bike in over 20 years. I'm learning to work on it...fluids, spark plugs and the like, but I'm no mechanic. With the darker days upon us, I've discovered the headlight does not always come on. I can tell it's not on now because the High Beam indicator will be lit if the headlight is off. Then other times the headlight will come on, so it's not the bulb. I'm guessing it's a problem with the switch? I've read through some of the posts related to headlights and switches, and from what I can tell, replacing the switch doesn't seem like the sort of job a neophyte should take on. Or am I seeing a mountain where there' s a molehill. Any thoughts? Thanks!

hiya wavery ....welcome to the forum

first off best to check the connector actually going to the head light itself .(brown wire is usually earth on these machines )

by the sound of it it lacks a good earth if both beams (high or low ) fail to ignite the headlamp .....

we have seen connector issues in that area before ,,,sometimes the best option is just to replace the h4 globe connector from the wiring loom .........there are available "ceramic connectors " which will survive higher headlight globe wattages .... inso much as many use higher rated globes which in turn burns the spade type connections in the connector ...

hope this suggestion helps

Sounds like a switch problem to me. What I did was without the battery connected so no sparks can occur. Remove the screw holding the switch block onto the handlebars (small x head screw underneath the assy Its not easy to see). Then with the switch hanging by its wiring soak it in some solvent (gas will do) and work the switches a bit and all sorts of gunk comes floating out. Remove it from solvent and dry gently with compressed air and see how it works, it often will start working and then get some CRC or WD40 and spray some into the inards. If it works great! if not you can pull them apart but do it in a clear plastic bag so as not to lose any small springs etc.
Still no go you can buy new from Motobins in UK.
It is common for the owners to put a 100watt bulb in the headlight which causes the switch to overload and melt some plastic parts then it is RS.
If you can do it get a Eastern Beaver Kit and put a relay into the circuit, this also gives you a ceramic connector like Charlie was saying. Putting a relay in relieves the switch of most of the load and makes its life far more comfortable and the headlight a heap better.
You need to remove the tank to unplug the wiring but other than that replacing it is fairly simple. Dont throw the old one they are good for spare parts.

First class good bloke that Jim from Eastern Beaver very helpful to deal with and the postal service from Japan where he lives is excellent. The quality of his wiring kits is extremely good. He used to own a K so the kit is a perfect fit for the bike. He makes a range of kits and I would recommend the heavy duty one with the ceramic bulb holder to allow the use of higher wattage bulbs.
Regards,
K-BIKE

Thanks all for the helpful advice and suggestions.

I must say I`m agree with Charlie on this one.....poor ground on the main bulb rather than a switch issue
.....since the high beam indicator shows but not the headlight.

Since it`s no ground connection at main bulb circuit, the current travels through high beam indicator to ground and this gives to much resistance to light the main bulb.



On the other hand installing headlight relays is a must on a K, the switch connectors and especially the
switches sooner or later goes down for count even with the normal load.

Inge K.

aye! read my thoughts inge .....



it might be a good idea as others suggested to check out the cabling (under tank) going to and from the switches as well.

a good friend out here had issues where the insulation on the wires was nonexistant ,,,this was near the under tank connections leading off to the handlebar switches in fact many of his connections were somewhat corroded .

i believe he got some deoxit just the other day ...and messaged me straight after he had applied it .....saying it was magic .

i have done the relay mods to relieve the wiring harness of high currents with suitable cable size ...the operation is normal but the switches are only switching a few milliamps instead of many amps these days ...works well and a highly recomended modification as many have suggested .

G'day Wavery ,
very similar problem happened to my 87 RS , high beam indicator on , no low beam , if I hit the high beam flash both low & high beam would come on , as K Freak pointed out when I pulled apart the handlebar switch it had overheated & the solder on the back of the switch had run a bit shorting out other wire terminations .

Ciao

JR

Melbourne Australia

K Freak wrote:
If you can do it get a Eastern Beaver Kit and put a relay into the circuit, this also gives you a ceramic connector like Charlie was saying. Putting a relay in relieves the switch of most of the load and makes its life far more comfortable and the headlight a heap better.
You need to remove the tank to unplug the wiring but other than that replacing it is fairly simple. Dont throw the old one they are good for spare parts.

Thanks for all the input. I'm going to spend some time next week working through the suggestions, but there seems to be general agreement that installing a relay circuit is a good idea. As I mentioned before, I'm new to working on bikes, but this job seems doable as long as I have the right parts. I assume Eastern Beaver can tell me what I need, then it sounds like removing the tank is the hardest step?

Thanks again all.
Cheers!

This link could become useful.

Inge K.