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Discussion Starter · #1 ·
I just rebuilt both front brake calipers. It had brake pressure before but now it doesn't. Not really anyway. Last 5-10% of the lever provides a bit. I've done a caliper rebuild once before on my 954rr. Maybe 6 months ago. Not totally new to this. I do bleed by hand, though. I went through a whole bottle and a half or so of fluid sloooowly bleeding left right and master cylinder. Half way through though, I accidentally ran it dry in the reservoir, not sure how much though. I will say, I got most results from the master cylinder. I bled for like a half hour more after I ran it dry up top. It's been putting out just fluid, no air, and I have basically no brakes. What should I do next?
 

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Discussion Starter · #3 · (Edited)
Well it's been a few days, haven't found any fluid leakage. Theres some small spots of dampness around the bleed nipple on all points I dried last night but thats just residual fluid from taking the brake line off. All the nipples are on tight, so are banjos.

I did remember that the new brake levers I put on did not provide as quick of a brake action... it looks like the pivot point hole (whatever its called) for the brake lever is deeper on the new levers and does not seem to leverage as good. So I put the old ones back on. I now have I would say... idk... 3/4 of an inch... maybe just barely a finger width worth of brake. It's enough to get around town with. Very spongy. Ill be upgrading to stainless soon. But somethings awry. I got a vacuum bleeder showing up today. Hoping its just air in a tough spot.

Last night I was playing with taking the spring clips off the calipers and noticed that if I pumped the brake now, it would build up to near where it's supposed to be. If I left the lever alone for 30 seconds (not moving the wheel... no rotor position change) it would go back down. Ive experienced this from moving the wheel (warped rotor) but I don't think I have had the pressure go up and down in one position before. You think it could be losing pressure from an air leak somehow even though I don't have puddles of fluid and the nipples/banjos all feel tight?

I will look today a bit closer and see if I can find any evidence of leaking.
 

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Discussion Starter · #5 · (Edited)
Odd that it worked a lot better until my caliper rebuild. I mean, it wasn't as good as it should be. There was always too much freeplay before the tension began, but felt within the shittier range of normal. Always felt spongy. But it was better than now.

I Just bled master, left and right calipers for a while... about 10 twists of the wrench for each. No change. Got 1 single bubble out of the left caliper at the beginning. Straight fluid... no leaking...

Ill have the vacuum bleeder in an hour or less. Maybe ill pick up some new brake fluid and give it a go. Wonder if I should shop for a master cylinder rebuild kit or just get a used or aftermarket new master. Master cylinders are one thing I haven't worked on before so I won't speculate on what could be broken since it's not leaking. My first thought goes to whatever the plunger is that the brake levers cup over. I guess I speculated.
 

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Discussion Starter · #8 ·
Yeah I'm surprised the bike still has original hoses. They are getting replaced for sure. Was beat yesterday. Working... Will try vacuum bleeding tomorrow and if nothing then the next move will be new hoses and a cylinder rebuild or replacement. Might even buy stock levers or reputable levers. Or just fill the pivot point hole on the lever with maybe like those jb weld metal puddies a little bit. Thank you.
 

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I have recently rebuilt my front callipers after the bike was stood for many years I know it had slightly spongy brakes before I put it away and had play in the lever similar to what you speak about,after bleeding for what seemed like an age and scratching my head till it was sore I realised my discs were warped and was never gona be able to bleed them.pull your lever in and look at both callipers see if onecaliper is gripping before the other you could notice that one side of your pistons in the calliper touches disc first and will see the disc move slightly indicating warped
 

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You can also try squeezing the air out. Take the cap off the reservoir. Hold the brake lever as tight as you can, then wrap the lever so it stays in place. Leave it like that overnight. I've done this a few times when bleeding doesn't seem to get all the air out and the brake isn't as stiff as I would like it.
 

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Discussion Starter · #12 · (Edited)
P
Not sure where in the US you're located but i have an extra master cylinder rebuild kit if needed. Located in Delaware
I can't imagine you mean for free. I am in Arizona. I will PM you. I am interested one way or another definitely. I have put SS lines on and bled for many hours and configurations, replaced bleeder valves... tried by pump and by hand... fresh fluid... and its bad. I took it for a ride today and actually leaving the highway coming to a complete stop (85mph or so to 0) I couldn't totally stop at the stop sign. I just turned and acted like I meant to lol. I stopped like I am used to stopping and it didn't quite cut it. It's fine for commuting around town but clearly not for taking it out for a good time. I am worried about breaking something pressing too hard and being screwed. The really weird thing is though, I am now having the similar problem with the back brake... in fact I have no back brake. I put in a SS line to the back. It has basically no fluid pressure coming out, constant infinite air bubbles. I can't tell what it's pumping air in through. Nothing is leaking. I have never had this problem with any bike. I put the oem hose back on and the back is acting the same. Really strange. I have bled brakes for a handful of bikes and never struggled like this.

The sucky thing is my fuel pump just went out on my 954rr. I have no car lol. I have to use the r1 until I get the replacement fuel pump installed, hopefully Wednesday.

One question... I took the spring clips off both front and rear. Could the lack of spring clip be contributing to the weak brake up front?

You can also try squeezing the air out. Take the cap off the reservoir. Hold the brake lever as tight as you can, then wrap the lever so it stays in place. Leave it like that overnight. I've done this a few times when bleeding doesn't seem to get all the air out and the brake isn't as stiff as I would like it.
I am currently doing this tonight.

The next time I work on the brakes (after I replace the fuel pump in the 954, lest a caliper seizes on me and I have no ride lol) I think I might be doing the reverse method with a syringe. Kind of curious how this works with two lines, though. Would I start on one end for a short bit, move to the other side, back and forth? Or just fill slowly all the way to the reservoir?

I have recently rebuilt my front callipers after the bike was stood for many years I know it had slightly spongy brakes before I put it away and had play in the lever similar to what you speak about,after bleeding for what seemed like an age and scratching my head till it was sore I realised my discs were warped and was never gona be able to bleed them.pull your lever in and look at both callipers see if onecaliper is gripping before the other you could notice that one side of your pistons in the calliper touches disc first and will see the disc move slightly indicating warped
The only reason I don't think this is from warped rotors, is when I pump the brake it gains lever pressure (without bleeding) and stiffens up and I get less and less travel in the lever... and then it loses it 10 seconds later. When I had bent rotors, it would lose pressure from moving the wheel. Also, no pulsing on brake. But OK, I will look at how the calipers are gripping.

PS I am no longer getting infinite bubbles in the front brake, like the back, after switching lines and bleeder valves. That is unique to the back. The front bleeds normal in the end now, and it just sucks keeping pressure and is very weak. The back will bubble every single time, forever, with zero lever pressure. I have swapped lines and bleeder valves for the back and it continues to suck ass.
 

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Discussion Starter · #13 · (Edited)
OK after a few hours of the lever zip tied, the lever got a lot more loose, so I tightened the zip tie up. Hopefully good news incoming. Just hope I am not sucking more air in.

Edit: cut the tie... lever seems way stiffer. Tied it up again. Hopefully it lasts. I wonder why I am having such a hard time getting air out with this bike... I have never had such a problem... God I hope it maintains pressure! I think tomorrow morning I will know for sure if it needs a caliper rebuild.

Now for the back, I am still stumped. It seems like a lost cause kind of bad. I can't tell you how many hours I have spent bleeding these brakes... days of work messing with shit. Weird.

Side note, anyone switch to dot 5.1? Hearing it is non-horrifying to paint has me sold but now I don't want to go through this again! lol. Sadly I already need to repaint the front wheel one day after all of this... touch up paint for now :whistle:
 

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What brake fluid are you currently using? Ok what is the method you are using to bleed the brakes? I like to use clear tubing I picked up from my local chain hardware store, makes less of a mess and it's fairly easy to see the fluid vs the air that has exited the system. The whole process was tedious for sure considering I pretty much do all of the work on my bike by myself, to keep the front brake engaged while i cracked the bleeder screw i used pipe cleaners around the front brake and just had to bounce back and forth. For the rear brake i found it best to not attempt to use my hand and instead i would pump it with my foot and i forget exactly how i kept the rear engaged. It took a couple of reservoir refills tbh but i may have gotten a tad bit of air into the system upon the refill process but i stayed persistent and eventually got everything working as it should. Definitely a whole lot easier if you could get someone to help out. You bleeding at the hand and at the caliper?
 

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Discussion Starter · #16 ·
My final method has been draining the system with a vacuum pump, and doing the refill by hand. First I vacuum out the master, then both calipers. Refill. Left and right caliper bleeding back and forth. I use clear tubing and 8mm wrench. Pump the brake 6 times steady but not rapid, hold, loosen bleeder, 2 seconds or so close back up, slowly release lever. I go back and forth each calipers, then do the master, then calipers again, then master again... yadda yadda. Like 10 bleeds each time before I switch to the other bleeder. Many reservoirs filled worth of fluid.

I'm starting to wonder if I'm using crap fluid. It's dot 4... comes in a yellow bottle. I forget the brand.

So I do think it needs a master rebuild. I think I'm going to end up getting new rotors, pads, master rebuild. Eventually. Maybe in a month. After zip tying the lever it IS better. It really did work. I'm tying it again tonight. BUT it still is not as good as it should, and it still pumps up and loses pressure without the wheel even moving. Something seems to be sucking air In. I think I might just zip tie the lever every night for a few... and when I am ready to bleed money again just do it all and do rotors/cyl rebuild/sintered pads/reputable SS lines/dot 5.1 or a hq dot 4. Admittedly the lines I'm using are el cheapo but I'm using the same lines on my 954rr and the brakes are awesome on the bike. And nothings leaking. So idk. This is one bike I really want to make sure I have great brakes on that won't surprise me.
 

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I'm guessing you still have air in the lines and your traditional bleed valve method is too slow. I would either install speed bleeders or get a vacuum bleeder and then remove the calipers and bleed them upside down, sideways, right side up and any other way you can think of to get the air out. I installed speed bleeders a hundred years ago and it makes bleeding super simple. Crack and pump. That's it!

Mark
 

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Just to relate, I was working on mine. Ran a couple resivours full on each caliper and up top bleeder. Then went around again. Then the next time, like a baby squirting out her who who, got an air pocket.

How the hell the air was that far up and so hard to get out....???

But I got it.
 
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