Sorry for the long post.

I’m no mechanic but have the will to at least learn some of the basics so I can understand my ride better and be able to do some of the work myself.

I was out riding this weekend and my buddy who I was riding with told me that my brake lights never went on. I found that kind of weird so I stepped on the brake pedal and wouldn’t you know it the brake light didn’t come on until I was practically standing on the pedal. That would indicate that I would have lock up my tires before the brake light went on. This is obviously not how it’s supposed to work and unsafe. After digging through this forum and google it appears that I’m not the only one that has experienced this issue before.

From all the info I read it seems I need to replace the brake light switch. I don't have a hand brake since the foot pedal applies both the front and back brake. Upon examing the bike, I’ll need a double banjo bolt pressure switch to replace the one that’s currently installed. My questions are about installing the new switch, bleeding the lines, and the type of fluid.

1) After installing the switch, do I need to bleed the brake lines?

2) If so, since both the front and back brake lines are connected to the same bolt do you just bleed one brake line at time and then do the other?

3) I’m not entirely sure what type of fluid is being used so is it best to just flush out the old stuff and replace with the type of fluid I want to use (DOT5)?

4) And with two brakes lines connected to the cylinder is there any issue of cross contamination when flushing? My concern is that after flushing the first line, some fluid from the other line happens to contaminate the line I just flushed.


Thanks in advance for any assistance.

 

I had typed-out a reply but lost it somewhere along the line. I hope this doesn't get posted twice.

Maybe your brake switch is mounted on the low pressure side of a proportioning valve. If this bike is only using one master cylinder....it should have a proportioning valve on in somewhere. It could be a defective brake switch, trash/debris at the junction of the line and the switch, or simply not enough pressure being developed in the single hydraulic circuit to activate the switch.

If you do not know what type fluid was in the bike to begin with and can't tell by the color of what comes out.....you better flush the system very well and go with one-or-the-other. Do not mix DOT5 with DOT4, 3 or 5.1. DOT5 is a silicone based fluid and the others are glycol based. There are disadvantages and advantages to both and people swear by whatever they use. I recommend DOT4, but don't intend to start a brake fluid food-fight here....so either will work. Just flush the system completely and then flush it again a couple of more times over the next couple of months. In your case....might not be a bad idea to completely remove all the lines and clean them individually.

When you bleed...start from the farthest caliper first and yes....if you open the hydraulic circuit up for any reason (like to replace that switch) you should bleed and in your case...flush and bleed.

It may just be a switch and that is what I would change first. That proportioning valve I mentioned is usually installed on single circuit systems to apply most of the force to the front brake caliper/calipers....just like on an automobile.

I can't say much more, as I do not know what model bike you have from the picture. It looks like a custom Shovelhead, but I can't be sure.

Hope the replacement switch works, but if it does not solve the problem, you may have to relocate the switch or even go to the earlier model mechanically activated switch. In the early models, when you press the brake pedal, it pulled a spring or rod to make the contacts in the brake switch and did not utilize brake fluid pressure.

Hope some of this helps.