I've got an 87 k100 rs that is currently suffering from a weird issue. Basically you can be riding along with low beam on and it will go off randomly. If I press the flash (for high beam) the light will come back on though. Also when riding I can put high beam on and the headlight will stay on all the time.

I've checked and replaced the headlight bulb, checked the earths on the bike and cleaned them up also checked behind the right hand switch and cleaned that up. Just wondering if anyone has any advice for what to look at next. It seems like a loose connection somewhere possibly but I doubt that will explain why high beam will stay on all the time.

TheJoker wrote:I've got an 87 k100 rs that is currently suffering from a weird issue. Basically you can be riding along with low beam on and it will go off randomly. . .  also checked behind the right hand switch and cleaned that up. Just wondering if anyone has any advice for what to look at next.

If the dimmer switch contacts haven't been checked, that's what I'd check next if it were my bike. Is that switch on the left side of the bar in the UK?

If your bike is fitted H4 halogen lamps greater than 55W/60W, it could be drawing too much current through the switch contacts, causing the contactm to heat up and shift position inside of the headlight switch.  If that is the case, the remedy is to fit a headlight relay.