Brake Light Mystery

[GeneralMilliron]

New owner of a 1985 K100RS. Love the bike (it's close enough to old school for me and a near color match to my '03 LT).

Here is the issue. Brake lights function inttermittently. At first I assumed loose wire, bad bulb, poor ground, weak battery, the usual suspects. Inspected, tightened, charged, etc. The issue still comes and goes while riding.

Then while troubleshooting in the garage, I was cycling the ignition key to test the lamp and noticed something (or was it just my imagination?).

It appears that the "firmness" with which the ignition swich is rotated to on, affects whether the brake lights function. A slow and gentle rotation and the brake light does not function (doesn't matter which brake is applied, for how long, or how hard). All the other lights (tail, turn, head) work fine.

If I twist the key firm and quick, the lamp works fine from both brakes.

OK... so my next thought is the circuit for the brakes is not getting power from the ignition switch or whatever relay is tied to the switch. But that is not the case. If I turn the key switch gently (any number of times in a row), the Fuse #1 powers, but the brake light still does not function. If I give the key switch a good twist, all is normal?

I am too old to read the wiring diagram.

Can this be possible?

Cliff

[bigbear]

On these old bikes the ignition switch contacts need an occasional cleaning. Not a terribly difficult job until one of the little springs vaporizes.

There is a good write up on the cleaning procedure at: www.ibmwr.org/ktech.shtml

Quite frequently you will also get random flickering on the instrument lights also.

Hope this helps

Roy

[jimajr37]

You might want to try this website: loads of good information and helpfull Gentlemen.
Jim

http://k11og.org/forum/

[GeneralMilliron]

The key switch was in bad shape. I cleaned up the contacts and all is normal now.