Brake warning

I have been riding an '82 XJ750 I just bought and have a few bugs to iron out on it yet.
The bike runs great and I have sorted out most of the wiring problems.
While riding and hitting a good bump my brake warning light will turn on.
It clears immediately when I reset it and the brakes work just fine.
The PO said it always did that and was not a problem.
I am thinking a short in the wiring to the fluid level indicator or something of that nature.
I would like to get everything squared away on my new XJ.
Could someone point me in the right direction?

 

My 82 XJ750 had the same problem. I drained the brake fluid from the reservoir with a syringe. Inside the reservoir there is a float that is on a round shaft, held on with a c-clip. I removed the c-clip and pulled the float off the shaft. Inside the float there is a doughnut shaped magnet that the shaft passes through. I found iron filings on the inside of the hole in the float where the magnet is located. I cleaned out the filings, put it back together and topped it off with fresh brake fluid. It has now been working for about two years with no problem.

 

Got the same problem myself. Cleaned the magnet off of the goo that had built up on it. Still no happiness. Light pops on and raises my heart rate every once in awhile. But nothing bad has happened in 6 months and I'm poised to rebuild the system here shortly so I haven't worried about it too much. Of course this flies in the face of being a safety nut but I have used a bit of risk management with this issue. When it happens, I immediately check my rear brake to see if it is functioning. Then I apply both brakes with the assumption that I will have enough time to stop using just the rear brake. Once stopped, I've reset and the light usually goes away. Usually. Once in a while it sticks around and turns off all by it's lonesome. Weird that way.

 

Thanks for the tip. I will be taking it apart this weekend along with the installation of brand new battery sensor kit to get rid of that pesky battery warning.
I have been on this site a week and is has already proved invaluable.
Many thanks!

 

Hey Maz, battery sensor kit... I think I might need one or advice on which port on the battery to plug the existing one into... where'd you get you kit, and do you know how to test the sensor? I have one... though it would go in the battery hole that read 6 volts on the multimeter (advice from friend), but still no love from the warning light (do I have to reset it after plugging in the sensor?). Thanks.

 

Blufish-The PO had the sensor kit still in the box. He never installed it.
As for advice, I've never put one in before.
An earlier post "82XJ750 battery warning light" has some great advice from much more experienced individuals than myself including how to get the warning to go off without installing the sensor..