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Discussion Starter · #1 ·
Hello, new to the forum. Just purchased a lightly used 2019 Duke 390 with 1400 miles. I am not sure if it’s because it’s been sitting or if this is the reason it was so cheap. For 4k for a low mileage 2019 with a tuner, exhaust and intake mod, couldn’t pass it up. I am have issues with the front brake, it happens very seldom. In the 4-5 hours of riding it’s maybe happened 5 times. The brake feels pretty squishy and a hand full of times I have went to brake and the lever went all the way to the grip with nothing, let off and compressed again and it braked. I tried to bleed it, no air came out at all after bleeding it enough to have to fill the reservoir 3 times. Still has a squishy feel, and has done it 2 times since I bleed it. Not sure what else to do, I have done some research but can’t find anything about it, is this a known problem with these bike? Thanks for any help! So far I love the bike, which is surprising coming from super sports and super motos.
 

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Welcome to the forum,
It is definitely not any common issue on these bikes.
It might have something to do with the ABS unit.
With OE breaded brake hoses and the second-gen standard with HH sintered pads, the brake feel should be solid.
 

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Discussion Starter · #4 ·
ABS can be painful to hand bleed because of the air traps caused by the hard line routing
Ah I see, it’s definitely got an air feel, that’s why I tried to bleed it. I am just gonna pull the gas tank and everything and bleed it at the abs module on both ends. If I can find my vaccum bleeder I made I may go that route, also could reverse bleed it. I have to re route the powertronics ECU harness anyways, the guy who owned this bike before me did not know what he was doing apparently.
 

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Definitely try reverse bleeding/filling the brakes. Otherwise, it might be a caliper issue? Any leaking at all underneath the bike at all when it sits? Even if it's just a drop here and there, it would be enough to cause a small bubble in the line.
 

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Discussion Starter · #6 ·
Definitely try reverse bleeding/filling the brakes. Otherwise, it might be a caliper issue? Any leaking at all underneath the bike at all when it sits? Even if it's just a drop here and there, it would be enough to cause a small bubble in the line.
No leaks what so ever, I used my vacuum tool to put vacuum on the reservoir and it seemed to tighten up the feel and it hasn’t happened since. Still compared to other bikes I’ve owned the lever seems to go a lot farther before it actually gets hard than I am used to.
 
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