"Brake" comes on at start up, and sets and resets intermittently XJ1100J

Having checked the rear master fluid level and the front fluid levels, the rear was a bit low so I added fluid about the site glass. I did notice that the diaphragm was misshapen nad would not return to a "flat" setting but would protrude into the cylinder area. I re assembled the master and test rode, continues to do the same thing. Of note is, that after several minutes of riding, the issue mostly clears up only to return immediately upon an engine restart. So today I dug thru the box of extra parts I got from the PO, low and behold , a decent looking rear master diaphragm. The rest of the master looks pretty rough. I cleaned it up and put it ont he bike expecting everything to be good, but warning indicator came on and reset it self twice before staying off for the rest of a short 6 mile ride. Partked bike, turned of the engine, counted to 10 and restarted. "Brake indicator came back on. Any one have any ideas?

Thanks

 

The brake indicator warns you of low fluid in the reservoir. It has nothing to do with starting and restarting the engine. You either have a faulty level switch or low fliud.
I have to keep my rear reservoir full to the top to keep the warning light from coming on.
Might be time to take the master cylinders apart to clean and rebuild them, should do the calipers too.
Remember your XJ11 has linked brakes rear to front. The pedal does the rear and one front, the hand lever does the other front

 

+1 on the switches if the levels are correct both front and back. The switches are wired in series and starting the bike is likely vibrating the marginal one enough to allow it to work just well enough to not flag a warning.

Since it is easy to duplicate you could disconnect one and short the two wires on the harness side. If it still fails reconnect that one and short the other one on the harness side. If after that it still fails then short both out to verify wiring and CMS are functioning OK.

 

Rooster 53, not sure what you mean by "+1 on the switches"
and are you saying that the front MC and the Rear MC have fluid level switches in them, wired in series, to trip the indicator? Which would make sense so either will alert you to an issue, but not so specific as to tell you which.

 

That means mlew suggested it and I agree

Yes, two bullet connectors for each switch that in their normally closed state ground the CMS line that monitors brake fluid level.

 

Yes, each master cylinder has its own float switch. either one will set the warning light off. They can be bypassed be plugging the wites together at each switch