Topic: what would cause the front brake not to accuate the brake light?

[smokeygold]

1975 CB550 front brake works fine however, brake light won't go on whan applied! Rear brake and light work fine.

[merc2dogs]

Bad switch or wire, rarely a clogged passage.

 Cross your brake wires with a short strip of wire and see if the light comes on, if they do the switch is bad, otherwise it's the wire and you have to trace it through to make sure connections are clean and tight, and that there are no breaks in the wires.

Ken.
 

[Jay B]

Plugged or bad actuator on the front brake line. Mounted on the bottom triple.

[Kevin D]

I had broken copper strands, hidden inside the wire jacket, behind the crimped connectors at the switch. It made for intermittent operation. I had to cut the wire back a little bit and splice in new - and very flexible - wire.

[Hope]

I have the same problem, but with my rear brake.

[old76cr]

Mine had a little corrosion at the connector at triple clamp. Unplugging it a couple of times and petroleum jelly solved the problem.

[OldSchool_IsCool]

In case you aren't sure where the switch is, look under and behind the headlight bucket, assuming you still have a stock configuration.  Follow your brake line until you find a large aluminum manifold.  Brake line to the front caliper exits the bottom and the switch takes up the top and exits to the rear.  Here is a (bad) picture. 

[Tower]

Shorting across the wires, may or may not indicate a problem with the switch.  For example, it doesn't rule out a break in the wires somewhere further towards the light.  

If shorting the  switch works, then it is the switch.  However, if shorting has no effect, then to be sure it is not the switch, unplug the wires and, using a continuity meter, measure the resistance across the switch ends.  Resistance should read infinite when not engaged, and zero when the brake lever is pulled.

[oldfordguy]

if shorting the wires at the switch has no effect, then you know for a fact that the wiring between there in the light is messed up (which doesn't rule out the switch being bad also.)  If it lights the brake light, then you know it is the switch (or the connectors on the switch.)  No need for a meter if you don't have one.

[Tower]

Like I said @oldfordguy, if shorting works (lights the tail lights), then both switch is bad and wiring is good. No further test is needed.

However, if shorting has no effect, then either: a) wiring alone is bad, or b) switch and wiring are both bad.  Like you implied, still need to test the switch.  I'm guessing you meant that to avoid using a meter, trace and repair the wiring, and if the tail light still doesn't work, one can assume the switch is bad?