TOPIC:

My 78 KZ650 rear brake light only works when the rear brake is used, not when the front is. Is this normal? If not, any ideas on how to fix this?

Ok,.. No,.. Yes,

Just so you know,...The rear brake's actuator is located on the other end of that spring that extends up from the brake pedal. It is manual, adjustable and easy to fix.

The front brake actuator is that 1 inch across bolt looking thingy with the two wires (brown and blue) coming off of it, screwed into the brake fitting on the hydraulic lines over the front wheel. It actuates off of pressure in the system and is not adjustable nor is it completely obvious if it is faulty/working or not.

It is normal for the front brake to require much more pressure than the rear to actuate the lamp. My rear brake will flash the lamp well before the brake is applied. The front brake however is opposite. Given the distance, I can stop the bike with the front brake without flashing the lamp. Screwed up huh?

Your problem might be the wiring or it might be the actuator.

Since changing the actuator means you need to bleed the brakes (messy, not tough, but still), I would check for faulty wiring or interrupted circuit first.

Key the bike on to where the rear brake light is functioning normally while the brake pedal is depressed. then->

Disconnect the two leads from the front brake actuator up there and cross (touch) the leads (this is essentially what the actuator switch does when it feels pressure in the front brake lines).
Note be sure that there is good clean contact on the wires here. It is an absolute possibility that dirty wire contact here could be the cause of your problem. Scrape the "varnish or patina" off of any questionable contact surfaces (it will interrupt the electricity flow). Including those contact surfaces. on the actuator itself.

This wire touching should cause the brake light to come on. If it does come on, then your actuator is not working. Replace it, bleed the lines () and you are good.

If it does not come on, then you have a wiring issue.

Wiring, completely different can of worms, keep us posted by posting for future help.

I am hoping that cleaning the contacts will do the trick.

Best of luck my friend.

You will love this. I got to poking around and started looking for the blue and brown wires. Found a brown on hooked into the actuator. And there was a blue one hanging by it. So for grins I plugged it back in with some di-electric grease and PRESTO. It works.

Qdude...YOU ROCK!!!

You're on his Christmas,Gift-List NOW!

Seriously though...gotta love an ending like that,right on.
If only ALL electrical problems were that easy.