Rear brake issue?

Hey guys so my rear brake pedal goes all the way down and does nothing. I have bled it multiple times and still no pedal pressure. I bought a new rear master and still no pedal... I don’t ever use my rear brake so I have no idea when it started. I do have ducabike rear sets on the bike and am running motul brake fluid.
The bike is under warranty but dealership is 5 hours away... has anyone else ran into this problem? Any suggestions other than take it to the dealership?

rear caliper has to come off and flip upside down from its mounted orientation otherwise air gets in there. Bleed it again like that and it will firm up nice. Otherwise take it to the Duc dealer and spend the $80 for them to renew the rear brake fluid for you

I had that issue. Took it in, they found one of the seals for a piston was leaking. Replaced the caliper and rotor on warranty. Week or two later, brake went soft again. Took it in, they bled it and whatnot on warranty. Went soft again, they bled it again.

Eventually gave another dealership a shot because the first one was kinda know for being garbage. Turned out, when they reinstalled the rear brake system after the warranty work, they installed something backward and that's why it was letting air in and going soft all the time. They swapped that one part around (whatever it was, didn't ask the question) and it never went soft again.

Might be an air bubble in your ABS module, those are hard to get out.

It’s an Italian bike, their rear brakes never work.

DucatiKev said:

rear caliper has to come off and flip upside down from its mounted orientation otherwise air gets in there. Bleed it again like that and it will firm up nice. Otherwise take it to the Duc dealer and spend the $80 for them to renew the rear brake fluid for you

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If I flip it upside down it will put the bleeder on the bottom... I’ll never be able to get the air out correct or am I misunderstanding what u are saying?

MaverickiB said:

I had that issue. Took it in, they found one of the seals for a piston was leaking. Replaced the caliper and rotor on warranty. Week or two later, brake went soft again. Took it in, they bled it and whatnot on warranty. Went soft again, they bled it again.

Eventually gave another dealership a shot because the first one was kinda know for being garbage. Turned out, when they reinstalled the rear brake system after the warranty work, they installed something backward and that's why it was letting air in and going soft all the time. They swapped that one part around (whatever it was, didn't ask the question) and it never went soft again.

Might be an air bubble in your ABS module, those are hard to get out.

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Thanks for the input. I’ll be moving soon to where the dealership is so hopefully a warranty issue!

T=2:45

DucatiKev said:

T=2:45

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Thanks man I’ll give that a try

I had the same issue and taking the caliber off and bleeding it upside down helped only slightly. Tried several times. Couple weeks ago I finally got the problem solved. I changed 2 things in the process, so I’m not sure which one did the trick:
1) Followed the bleeding instruction from the service manual (page attached). ”Before bleeding a brake master cylinder, move back the calliper pistons to let any air buildup in the ABS control unit flow into the master
cylinder.” Note that when you push the piston all the way back your reservoir may flood over because the fluid is pushed from the system back to reservoir. If the reservoir cap is not open and you have max fluid level, then you won’t be able to push the pistons back much.
2) I used for the first time air compressor in the bleeding instead of pumping the brake lever. So the vacuum pull from bleed nible vs pressure push from master cylinder might have also moved the air in the system differently.

I had an issue with my system when i added my rear sets. what i believe happened to me was my brake system was not bled well to begin with so when i added the new rear sets, i was too aggressive with the stops in order for me to get enough pressure to get the rears to work. Problem is when i was at the track, i was dragging the rears slightly and over-heated the system. So a PSA to the group to spend the time to make sure you bleed the system and set the stops appropriately.

You dont need rear brakes

1299rFE said:

You dont need rear brakes

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you are so right. at the track i never touched the brakes which is why i was surprised i saw an issue on my V4.