Headlight dimming/flickering

[E30_Crazy]

Bike is an '85 K100,

Was out riding the other night, and noticed the headlight would go dim sometimes. I finally narrowed it down to only being repeatable with higher RPMs/acceleration. I don't think it's a short or loose connection. The roads here are crap, and no amount of bumps, potholes, heaves, or cracks in the road could replicate the dimming.

The only other issue I've noticed, and thought was maybe a bulb or switch issue, was when switching to high beam. The low beam went out, but the high beam did not come on/flickered out. Kind of unnerving going down an absolute pitch black forested highway at 60mph!

Anyways, could an alternator and/or brush cause this, or do I need to dig deeper into wiring? (AGAIN).

[E30_Crazy]

Oh, and the ground through the starter too. Easiest way to check? Is it a cable and bolts ground, an internal ground, grounded just by being mounted?...

[Inge K.]

A typical symptom for worn starter brushes/ and or dirty starter commutator.
To verify....ground the starter input terminal...then your headlight should behave normal.
Don't even touch the starter button as long as the starter input terminal is grounded.

[E30_Crazy]

Any pictures or a previous thread for me to reference? I tried searching before I posted, but didn't find any similar topics

[Laitch]

Any pictures or a previous thread for me to reference?

Start here. Then read from this post and the ones that follow it. There's this post with photos of the starter components. Then, from our Technical Library card catalog in the Electrical section there is this and this.

[Vespa no more]

You feeling okay Laitch?

...No imogees.

(insert smiley face here)

Guy