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Discussion Starter · #1 ·
Hi everyone,

I have an issue with the rear calliper on my duke 790. I noticed that the pads were pressing into the disc quite badly, when going for a ride there was lots of brake dust left behind on the wheel and some discolouration on the disc itself.

So I thought a good cleanup would help. So, I took the pads out, which was very difficult due to being so freaking tight, and took off the rear wheel etc. Then took the assembly off.

But when extending the piston, it looks good and no corrosion. But the issue is I can’t return it to normal? Normally you can do this with just hand pressure but it won’t budge, not even with a clamp. the piston looks good, no rust or major grime, however its just seized. Although, you can pump the break and it will extend..

Also, the fluid looks good.

So am I likely going to have to do a brake rebuild here? I’m not sure what’s going on really. My technical knowledge is limited, but everyone should be able to clean a calliper... a rebuild might be pushing my skills somewhat.

I did notice that the rear brake lever as no free play, could this be causing the piston to not to return to flush? I dunno...
 

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Have a look around the brake lever, you could have a stone or something that has jammed in the mechanism (some Kawasaki's have had this problem).

If all else fails you can relieve the pressure at the brake bleed screw, remember to put a hose over the nipple leading down to a countainer otherwise you will have brake fluid everywhere.
 

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I did notice that the rear brake lever as no free play, could this be causing the piston to not to return to flush? I dunno...
Yes, absolutely. If there's no free-play, the "fluid return holes" are not exposed properly and the brake caliper will seize

Adjust the pedal for proper free-play and you may solve the problem
 

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There was a recall on the 790 Adventure for a similar problem. Loads of free play on the lever but the piston would drag alarmingly. The dealer changed the disc and pads and it still did it. Apparently the metal part of the brake line as it enters the caliper wasn't long enough and brake pressure built up and couldn't return to the reservoir. No idea if the recall worked as I sold the bike before I could get the work done.
 

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Discussion Starter · #5 ·
Thanks guys!

I adjusted the free play and that seems to have done it. I was able to push the piston back under hand pressure only. So that’s great And now its clean as a whistle after some break cleaner!

Just another quick query, I noticed in the manual that the back brake line goes from the calliper up to the abs unit, then back down to the foot brake. It does see, that the fluid after pushing out of the calliper is now nasty, certainly worse than I initially saw. So I’d need to do a bleed. The question is, how much Dot 4/5 fluid would I need for this. The reservoir is small, bet there’s a lot of cable?
 

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The question is, how much Dot 4/5 fluid would I need for this. The reservoir is small, bet there’s a lot of cable?
Depending on what's available to you.

One 250ml bottle is more than enough. In fact, that would probably be enough to bleed front and back. If you're going to do both get 500ml to be safe and save a 2nd trip to the store.
 

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Discussion Starter · #7 ·
Depending on what's available to you.

One 250ml bottle is more than enough. In fact, that would probably be enough to bleed front and back. If you're going to do both get 500ml to be safe and save a 2nd trip to the store.
Thanks! I can get at dot 5.1 motorex 250 ml, so that should do it!
 

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So, I took the pads out, which was very difficult due to being so freaking tight, and took off the rear wheel etc. Then took the assembly off.
When you did this, how much of a gap was there between the pads and rotor? I'm getting a ton of brake dust on my rear wheel just riding around, so I'm trying to figure out if this is something I can do, or if I need to bring it into the shop to get looked at.
 

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Discussion Starter · #9 ·
When you did this, how much of a gap was there between the pads and rotor? I'm getting a ton of brake dust on my rear wheel just riding around, so I'm trying to figure out if this is something I can do, or if I need to bring it into the shop to get looked at.
Hey,

There shouldn't really be any gap. The disc should be touching the pad. But mine was biting in and all I needed to do to fix it was change the break fluid. It seemed that the piston was a bit stuck, once i flushed the system then it freed up and worked like it should.

I would wiggle around the break calliper and see if it frees the pad a little, it could be sticky or could just be a fluid issue. You should be able to press the pad back off the disc with hand pressure alone. I guess if you don’t see the pad being able to move in and out then it's likely that it's stuck. I just looked on youtube on how to fix a stuck pad, that gave me all the info I needed. Plus its much easier to see it being done than explain it etc.

Its not a hard job to do, cleaning your callipers etc. I would give it a go if your interested in working on your bike.
 

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I would wiggle around the break calliper and see if it frees the pad a little, it could be sticky or could just be a fluid issue. You should be able to press the pad back off the disc with hand pressure alone. I guess if you don’t see the pad being able to move in and out then it's likely that it's stuck.
Perfect. I'll give this a go tonight. It's really close and I'm not seeing any movement with brake lever usage.
 
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