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Discussion Starter #1
Hi one and all -

Recently bought a 2000 650c, and need to do a bunch of work on it to get it roadworthy. I did the fork seals yesterday, today wanted to get the rear brake working. There was no brake feel whatsoever so my first step was to bleed the system. Attached some hose onto the bleed valve, pumped the pedal, held it down, cracked the valve and closed it again.

Repeat for over an hour...

About an inch of very dark (almost black) fluid came into the hose, that's it. Figured there was a blockage somewhere - unscrewed the bleed valve completely, pumped the pedal - nothing. No fluid came out at all.

Then tried loosening the banjo bolt on the caliper - no fluid came out of that, or the caliper.

Removed the brake line completely, tried blowing some air down there and it seems to be ok, unblocked.

I have no idea what to try next. Pumping the brake pedal has no effect at all, and whatever fluid is in the system is black as the ace of spades.

Any help would be very gratefully received!

Thanks,

- J
 

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Probably want to rebuild the Rear Brake Master Cylinder, at the least.

Rebuilding the Rear Caliper might not be such a bad idea either; even if you can bleed the system after rebuilding the Master Cylinder.
 

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Discussion Starter #3
Ok, this'll sound like amateur hour but man that's how I roll...

The master cylinder, that's the metal cylinder, bolted vertically onto the frame?

Be gentle...
 

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That's it, yes.

New, we Merkuns don't know nuttin' about you Canadanians and your 650Cs, but I'm going to go out on limb and say that the C has the same master cylinder as the A.

What you need looks like this: https://www.amazon.com/1987-2005-Kawasaki-KLR650-Cylinder-Rebuild/dp/B005PHCLL4

Is the front brake OK? You might figure it is in need of some help, too.

Not to be a Gloomy Gus but, if the master cylinder is all gunked up, the calipers are probably in need of a cleaning and perhaps a rebuild, too. I'd at least pop the pistons our and clean everything real good.
 

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Discussion Starter #5
Oooh, that might suck - here I am with my fancy but beaten up 650c and y'all don't got them south of the border. There could be trouble ahead...

So you guys never got the C model in The States? It's a snazzy little number - different front fairings, smaller, leaner tank, me I love the look of the thing. Crusty she may be, but there's gold in them hills...

Thanks for the info on the master cylinder Tom, I really appreciate it. I have a little experience now after building my '81 Honda CB750, and am no stranger to asking questions on forums either - just ask the very patient folk over at dotheton. Man they got some questions from me alright, barely knew a carburetor from a clutch plate when I started that build. So taking the caliper apart shouldn't be too much of a problem but I do like me a good video - I'll see if I can find something on youtube to walk me thru it. The master cylinder however is virgin territory. Thanks for the link, I'll take the thing apart tomorrow and report back on the state of play.

One thing - popping the pistons out. Doable with some fluid/hydraulic pressure in the lines, but without it? I don't have an air compressor - trip to my local shop and ask them to do the honours?

Good man, thanks fella
 

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WOW! Brain fart! I was just over on the Versys 1000 forum before I jumped over here and read this post. I almost posted that it might have something to do with the ABS but I caught myself just before I looked foolish ;)
 

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One thing - popping the pistons out. Doable with some fluid/hydraulic pressure in the lines, but without it? I don't have an air compressor - trip to my local shop and ask them to do the honours?
If you are gonna have the front brake apart to service it anyway, you can just use the front master cylinder to pop the pistons out. Or, they will pop out once you get the rear master sorted out.

If any part of the brake system is suspect, it's highly likely all of it is. I'd be tempted to tear down both systems and show them some love. Relatively easy and cheap work...and it is your brakes after all. :wink2:
 

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Discussion Starter #8
Finally (after a couple of false starts and wrong parts) received the rebuild kit for the rear master cylinder - assembled the thing but still no dice.

I have no idea what the problem is - with the cylinder bolted onto the frame, the brake pedal attached and the reservoir connected to the cylinder (but without the line to the caliper connected) there is no fluid coming out of the top of the cylinder when I pump the brake pedal. Nothing at all. Is there something I can check? If no fluid is moving through the cylinder then none would move through the brake line to the caliper, correct? Really want to get this thing fixed!

Any help would be amazing, thanks guys
 

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Is there something obstructing the low from the reservoir into the master cylinder?

Perhaps there gunk in the bottom of the reservoir, in the hose, or in the banjo bolt.

Do you have firm pedal or does it move with no resistance?
 

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Discussion Starter #10
Is there something obstructing the low from the reservoir into the master cylinder?

Perhaps there gunk in the bottom of the reservoir, in the hose, or in the banjo bolt.

Do you have firm pedal or does it move with no resistance?
Nothing obstructing anything (I totally cleaned the whole master cylinder and hoses etc)
No gunk anywhere (and the banjo bolt is not connected at this time, just the reservoir to the MC)
Firm pedal I guess, no resistance

??
 

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There are 2 holes under the plastic elbow which feeds fluid from the reservoir to the master cylinder piston. The big hole is lower and only allows fluid to lubricate the piston shaft and outer seal ring and prevent a vacuum from being behind the piston cup.

The upper fluid hole, which actually feeds fluid into the system is Sooo Tinnnnnyyyy that many people miss cleaning it out. It most likely has some gelled or crystalized old fluid blocking it.
It is sooo smmmallll, I don't even know what size it is. I use a natural gas or propane gas jet broach to poke thru them. My #80, .0135" wire gauge drill bit is too large.
We do Not want to create a burr inside the piston bore, which would damage the new piston cup.

I think Amazon used to sell a 5 pack of the jet broaches. Or contact your local NG or LPG service professionals.
 
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Nothing obstructing anything (I totally cleaned the whole master cylinder and hoses etc)
No gunk anywhere (and the banjo bolt is not connected at this time, just the reservoir to the MC) << When I said 'banjo bolt' I meant the plastic elbow on the end of the reservoir hose. T.
Firm pedal I guess, no resistance

??
In my way of looking at this the 'firm pedal' issue is an important diagnostic, so we need to make sure that we define our terms and have a mutual understanding of why I ask.

If you can press down on the brake pedal and it does not move but a little bit and requires a fair amount of force to move, that is a firm pedal (making sure, of course, that there is no mechanical reason why it doesn't move). It indicates that there is pressure inside the master cylinder and there fore, probably, fluid.

The issue, then, is that the fluid can't get out and you must look downstream from the master cylinder piston at the internal passages in the cylinder, the banjo, the brake line, and the caliper.

If you can press down on the brake pedal and it moves down easily or has a very spongy feel, that indicates little to no pressure inside the master cylinder. Therefore there is probably no fluid getting into the cylinder and you need to look upstream from the piston at the internal passages, the connector, hose, and reservoir.

The first thing I'd do, though, is what Paul says. You'll find KLR wrenching is always easier if you listen to Paul and do what he says first. Gibbs Rule #5.
 

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Discussion Starter #13
Gibbs Rule #5 - I'm all over that like a hobo on a ham sandwich. Thanks for your advice gents - I remember seeing that tiny hole but also remember thinking nothing of it. I'll see if I can dig out some filament wire or a Jimbo-matic-pokey-thing and see if it's blocked.

I'll be back...
 

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Discussion Starter #14 (Edited)
Ok, got a tiny needle and poked it through that tiny hole. Pretty sure nothing was blocking it, but certain now. Rebuilt the the cylinder for the tenth time, still not working.

To clarify - as it sits the rebuilt cylinder is bolted to the frame, and connected only to the pedal and the reservoir (which has fluid in it). When I pump the pedal, I see no no fluid squirting out of the top of the cylinder (where usually the brake line would be bolted to the cylinder with a banjo bolt). With it set up like this, when I pump the brake pedal should I not be seeing brake fluid pumping out of the top of the cylinder?
 

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Yes, you should. That means that fluid is still not flowing from the reservoir.

I'm going to have to say that there blockage in the wee hole @pdwestman described. Honestly, if that hole won't pass a .013" wire I don't think poking it with a needle is really going to clear it if it is blocked. You need to be able to see light through it. Shine a flashlight down the bore; if it is clear there should be a pinpoint of light visible.

Is the cap on the reservoir? If so, take it off. Without fluid in the cylinder there may not be enough force to overcome the vacuum created by the diaphragm in the cap.

Usually on hydraulics I prime everything before assembling to avoid that sort of thing. You might try that.

Another possibility (I tried to think through this, but my head exploded) is that you need a bit of back pressure. Put your thumb over the banjo bolt port and try that.
 

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Is there any possibility that the piston cup was installed up-side down?

The Larger flared end of the rubber piston cup would need to face UP. To scoop the fluid into pressure.
 

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Another possibility is that the piston in the master cylinder is not going down far enough to expose the inlet port from the reservoir. This would keep the cylinder from filling with fluid and thus no fluid would be pumped out. Try disconnecting or adjusting the linkage to the brake lever so the piston can go down fully.
 

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Discussion Starter #18 (Edited)
Thanks again gents for helping me try to figure this out, I really appreciate the insight and advice.

Tom, tiny hole def not blocked - managed to poke a tiny wire right through it. Cap is off the reservoir, but I will try the thumb-over-the-port trick and see if that helps. I'm not sure what you mean by prime everything before assembling though?

pdwestman, good catch, but the rubber piston seal is on the correct way (I just double checked!)

GoMotor, I'm going to try that as well, but pretty sure the piston is going down fully.

Thanks a million guys, really hope to get this figured out. Can't believe it's taking me so long to get this thing working!
 

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The working lip of the rubber piston cup needs to retract down below the Tiny Little hole.

With a light shining into the banjo bolt fitting one should be able to see light change to dark as the piston is actuated. Loosen the 12mm nut on the shaft and remove clevis pin attachment to adjust, if needed.
 

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Discussion Starter #20 (Edited)
Considering that there is no fluid in the mc only the reservoir at this point, would the fact that the mc is full of air be the cause of the problem? I'm really not sure if I'm making much sense. It's just that I've tried everything now and cannot get any fluid moving through the mc no matter what I do.

Would pouring some fluid in through the banjo bolt port at the top of the cylinder (with the cylinder bolted to the frame) do anything to get the thing working?
 
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