headlight no workee

[kaput]

Greetings one and all,

On my 1985 K100RS the headlight stopped working though the flasher briefly kept on functioning before it also died.

I replaced the headlight bulb and the left hand switch and now only have the left signal functioning.

Am I right in presuming that it might be the starter which needs to be cleaned so that the load shed relay can pass the power to the headlight?

Or are there other possibilities?

Your input is much appreciated.
 

[Inge K.]

Check if you have power at the white/yellow wire in the connector under the tank.
Have a look at this thread.

If the LSR is the problem, your horn and turn signals won't function either.

[kaput]

Thanks. That is very helpful. Will check.

[Inge K.]

Easy test for the LSR.....turn on the ignition, ground the starter input terminal, if the headlight now functions
the problem is the starter brushes.
And of course, while doing this test.....stay away from the starter push button.

[kaput]

Problem solved.

I had communicated with ReneZ - forum member who lives nearby - and Rene had agreed to come over and help me troubleshoot the problem.

Forums like this are wonderful aren't they.

While waiting for Rene I followed Inge K.'s prescription for testing the switch (thanks again Inge) and although I determined that the switch was good I was not absolutely sure I had not done it right so I went ahead and removed and then cleaned the starter. The starter had a fair amount of black gunk on the commutator but nothing serious enough to explain the problem.

About the time I finished cleaning the starter, forum member ReneZ arrived on his 85 K100.

Rene and I had never met before but it quickly became obvious that he really knew his way around a K bike.

Rene checked the switch (good) and checked and reinstalled the starter. No light. He next used his multimeter to check the relays, found one as suspect,  switched two relays, and presto there was light.

So the issue this time was a bad load shed relay.

Thanks ReneZ!