Front Brake Master Cylinder

[dirty jim]

Noticed my brake light was on this morning. Felt the lever, it "rattles", push lever out, light goes out. OK, loosen lever bracket, wedge lever to brake on position. Reassemble making sure tab is in notch, both brackets (lever and throttle) are touching, still no good. Take it apart and look at master cylinder piston and it has a gap between it and the lever. Tried cycling it with lever thinking it was stuck, still no luck. Any knowledge out there? Oh, it's a 2015 FXDL.

[TexNorth]

If I understand the symptoms, sounds like the piston is sticking, not allowing it to come back to rest position or the spring behind the piston is broken and not pushing the piston back.  There could even be some debris that is stopping the piston from coming all the way back.

One other thing. check if the part of the lever that pushed the piston in is broken off.

[dirty jim]

Thanks TexNorth, that's what it seems like to me. I've hosed it down with Brake Cleaner while pushing the piston in and out, nothing. I don't think it's a broken spring because it does come back some what. I've taken the master cylinder cover off and squeezed the lever, and I don't see the "geyser" of brake fluid. Master cylinder rebuild time?

[rigidthumper]

The rebuild kit comes with a new spring, which typically fixes this issue. Before spending the $, try a drop of cable lube or 3 in 1 oil on the plunger. Sometimes it's just a little sticky.

[dirty jim]

Thank you both for the education. Tried the 3 'n 1 rigidthumper, no difference,  looks like I'm spending money and rebuilding a master cylinder

[TexNorth]

You probably are not seeing the geyser because the piston is starting it's movement when it's already past the large hole. Rigidthumper has a good idea.  Try lubing it.   

The spring could still be broken in that the break "shortened" the spring but will still push it back some ways.

Other than it magically starts working after lubing it, looks like it's time to tear it down and rebuild it.   At least that way you can see what is going on.

- looks like you already did it -