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Topic-icon Front brake switch question R100/7

  • jcrife
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2 weeks 1 day ago #5929 by jcrife
Front brake switch question R100/7 was created by jcrife
On my 1978 R100/7, I rebuilt the master cylinder, put on a new brake line from Bobs, and have bled the brake, used DOT4, and all seems well. I have not put the tank back on yet. Is there a way to test if the brake light on the dash will go out before putting the tank back on.....will just turning it over do it? I have only turned on the ignition and it is on as it should be.....just want to avoid taking the tank on and off more if I can. Also, the 2 electrical leads which connect to the brake switch....does it matter which male spade they hook onto to or just one to each? Thank you.

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2 weeks 1 day ago - 2 weeks 1 day ago #5930 by Wobbly
Replied by Wobbly on topic Front brake switch question R100/7
Obviously, I'm in front of the computer with my hair in curlers and my bunny slippers on, and not looking at my dash...

► But the light comes ON for only 2 reasons:
• Key turned ON for indicator lamp check
• Low brake fluid level (which is determined by the switch in the reservoir cap)

So yes, in my mind you need to start the bike. Neither of these 2 reasons is based on the Brake Lamp Switch to which you refer.

► No, there is no difference or special polarity in the 2 terminals of the Brake Lamp Switch. Any wire to any terminal is good. This can be tested by simply turning the key to the ON position and pulling on the RH lever.

A funny thing about this setup is that air in the cylinder will gather at the Brake Lamp Switch, instead of rising to the reservoir as it should. So you may need to find a steep downhill portion of your driveway, stop the bike there, and slowly pull the front brake lever 10 or 15 times to chase out the final bits of air. This is because the M/C is canted rearward due to frame mounting.

Hope this helps.

Don't hide 'em, Ride 'em !!
Last edit: 2 weeks 1 day ago by Wobbly.

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2 weeks 14 hours ago #5937 by 13807
Replied by 13807 on topic Front brake switch question R100/7
Jcrife, I'm not sure if you are inquiring about an issue with an annoying always on dash light. In particular the light for the brake fluid level. I had this problem with my 1980 /7. All worked fine with the tank off but when I put the tank on, and tightened it down, the dash light would come on. I'm not sure if the metal on the underside of the tank was shorting the leads or if the lid on the rez was getting tweaked. The final solution was to add a couple washers between the frame and the round rubber piece of the mounting hardware. This lifted the tank enough to where there was no interference.

Wobbly, I hope the slippers and curlers are not a result of the self isolation or Covid 19 symptoms. Stay healthy, you are an asset, in many ways.

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