Bleeding brakes

Does anyone know how much brake fluid my xj750 will take from empty ?

Also just how long does it take to bleed the brakes, seems like I been at it for hours !

 

I'm fed up with the old bleeding procedures. Snagged me a speed bleeder and will test it out on Friday.

 

Bleeding the brakes on these old Japanese bikes can be a huge PITA, especially from a dry master cylinder. A vacuum bleeder will definately help, otherwise there is a couple things that you can do.

1. Fill the master cylinder (obiously)

2. Open the bleed screw (put a small plastic tube on it to direct the fluid away from all painted surfaces)

3. Pull the lever all the way to the handlebar

4. Close the bleed screw, and release the lever.

The trick here is to get that plunger to fully return to the released position with no fluid in the lines. Air is compressible so you can pull a pretty good vacuum and never get anywhere. The trick that I learned on my Suzuki (haven't started from scratch on the XJ) is the wiggle the lever against the plunger to get it to pop back out. Once it has fully extended back out, start over at step (1) until there is fluid without bubbles coming out of the bleed screw and the lever is firm.

Always, always, always make sure that there is fluid in the master cylinder during this process. Otherwise you'll just keep chasing your tail and never really get anywhere.

HTH

 

Hi chav' there isn't a set amount of fluid, when you finished bleading, just fill to the line & yes it can take foreeeeeever.
What part of Wiltshire are you from? Wiz.

 

A vacuum bleeder is the only way to go.
Slip the hose on, a couple pumps and you are done.
Go from totally dry to fully bled in less than 5 minutes.
Make sure you don't suck the master cylinder dry or you'll be starting over.

 

This sounds interesting. The bleeders are the small round things that are on the front brake assembly sticking up towards the handle bars right?? They got tiny holes on the side and small threads sticking into the rotor right??

 

Mike & pvt... Thanks for the heads-up on the vacuum bleeder. I have one on the way since I want to flush and bleed the brakes. Inevitably I end up spraying brake fluid, so that should make it much easier.

 

Any reason these things can't be gravity bled? Before I bought my MiteVac I would hook a hose to the bleed screw, make sure the master cylinder was full, open the bleeder and keep adding to the master cylinder. It would take an hour or so but eventually fluid with no bubbles would come out of the bleeder screw and all was good. This assumes that the master cylinder was bench bled prior to starting the procedure.


You can perform other tasks while bleeding the brakes this way just make sure that the master cylinder never goes dry.

Wamaxim

 

They can be gravity bled if there is fluid in the lines to start with. If they are dry (and the caliper), you'll never get anywhere from my experience.

 

Start with the caliper farther away from the resivior. i use a piece of air bubbler hose from a fishtank or clear vacuum tube works as well. you want to connect it to the bleeder valve on one end and place the other in a skinny jar or skinn glass you dont care about. keep the tube at the bottom of the glass.

pressure bleed till you get the air out of the tube and make sure the bottom end of the tube stays in the fluid (it cant pull air back in if it cant get it in the tube) leave the bleeder barely open to allow pressure flow through. Keep the resivior full when bleeding. bleed till clean fulid comes out. then switch sides and repeat.
(brake fluid cannot have any moisture, dirt or air and remain effective)
use DOT 5 if you can find a bike shop in your area that has it the increased pressure will give you a little extra stopping power.

I always bleed both sides and then do them both again, you want as much clean fluid as you can get or you will be doing it again in the near future.

 

Huh. Useful!! Can anyone tell me where my master cylinder is on my XJ700?? Where i refill my brake fluid?

 

right next to the front break leaver the square box with two phillips screws in the top.

 

MityVac rules! My TIME is worth more per hour than that thing cost and it's a real mess preventer too.

 

Cool! Found it! I feel pretty stupid currently! lol

 

we all have our days mine was yesterday when i had to have 10 people drill onto my head that i had fixed a wiring problem by accident before i believed them.

 

Never, never, never mix DOT 5 brake fluid with DOT 3 or DOT 4, they are not compatible at all. In fact, a chemical reaction will occur and solids will precipitate out and plug ports. Instead, DOT 5.1 can be mixed with the other polyethylene glycol based brake fluids (DOT 3 and 4). Harley used to use DOT 5 brake fluid (I used to be an engineer for their primary braking system supplier) since it has a higher boiling point than DOT 4, but the availability and costs drove them back to using DOT 4 brake fluid among other reasons. Generally, the DOT number is the boiling point, in hundreds, of the brake fluid.

 

thanks PV i should have mentioned to sue non sillicon based fluids

 

I'm from Trowbridge Wiz, you'll see me at the George in Longbridge Deverill most Tuesdays when the evenings are a bit longer.

So Far I've filled the reservoir, pumped the lever with a tube on the bleed nipple until bubbles come out. The level in the reservoir is not going down at all.
I've tried reverse bleeding, by pushing fluid back up the lines, but when I pump the lever all I get is air bubbles.
I've just changed the pistons, and brake pads. I've used about 250ml of brake fluid so far, but it seems to vanish into thin air !

Vacuum kits cost about the same as if my mechanic does it, but I want to build this one myself.

 

I am not sure what vacuum kits you considered, but I have this one on the way for $30.

http://www.amazon.com/gp/product/B000FUMWTM

Seemed pretty cheap to me for something that will save me quite a bit of aggravation.

 

I was going to ask which DOT to use, and then saw my master cylinder already has the answer on it. I will be topping mine off once I get one of the stripped screws out. Considering I don't want to take one out to go get a match, does anyone know the size of the two screws in the cylinder so I can just put new ones in?

 

Hi Chav' we need some more background, like did the brakes ever work, have you cleaned / overhauled the master cylinder / calliper pistons, brake lines?

I had a lot of the Wiltshire bikers working for me when I converted the old Roundways loony bin in Devizes.

Good luck with your brakes, if it is any comfort, I have stopped bleading the brakes on my project Kawa' as they are still spongey, I thought I would let them settle for a week or 2. Wiz.

 

Been there done that.
http://www.xjbikes.com/Forums/viewtopic/t=15859.html

 

When I got the bike, the brakes were seized on. I drained the system ( pumping worked ) and found that the pistons were in a very bad way. I replaced the pistons with stainless ones, and also the pads and all the copper washers.
Now I have the problem !

 

Sorry to resurrect this thread. Or also for not starting my own. But I got a new MC and new lines. I bled my brake the usual way, got all the air bubbles out (or so I think) and i keep filling the MC (never let it run dry) but the brakes do not build pressure. I am bleeding all 4 bleeders. I am not getting any more air out of either four bleeders (I have anti dive system) Am I supposed to, or is it absolutly neccesary to fill the MC and then "CLOSE" the MC after you get the air bubbles out, in order for the system to build pressure? Because I have been doing it with the cap off the whole time. (never letting it run dry of course) Please help.

 

How come you have 4 bleed valves?

 

I have the anti dive system. They are below the calipers. The instructions says to bleed those first. and then the calipers. They are integrated.

 

Try bleeding the banjo bolts...

Technique is the same as bleeding the bleeders ie. pump the lever until you get some pressure, then ease the banjo bolt slightly. A hiss or bubbles will come out (keep the lever back to the bar, do not release). Tighten the banjo bolt up and repeat for all the banjo bolts (even the one on the MC). If you can't get pressure to build up, bleed the MC banjo bolt first until no bubbles come out and move along the line to the banjo furthest from the MC. Good luck and keep a lot of water on standby as a lot of brake fluid will spill from the banjos. Also use eye protection as the banjos can squirt you good. I use a squirt gun and wrap the banjo I'm bleeding with a rag. Just listen for the bubbles escaping...

After you get good pressure, bleed the bleeders.

 

Thanks classic racing. But, I am getting decent quirts coming from the bleed valves. I will nevertheless try the banjo bolts as well. My main question above was:
Is it necesary to keep the master cyl. cap close while bleeding the brakes? or can I do it with the cap off?

 

I usually set the cap back on to prevent geysers. You don't have to have it screwed on, just don't get violent with the lever.

 

Yup, bigfitz is right. I forgot that one. No need to screw it on, just leave it loose

 

I tried Classicracing's advice and it released the remainder air in the system. Finally build up pressure. Thanks fellas.

 

Just did a complete brake job on my bike this afternoon. Knew I needed to flush out the 27 year old fluid so I went ahead and bought a Mity-vac. I am thoroughly impressed with how easy it made the job.

I highly recommend one or at least find a buddy who has one

 

Yep, after I finished the job my buddy 's friend told me he had one and it makes the job soooo much easier. I'm going to look into buying one in the near future.

 

I picked mine up last week at Autozone for $30. It actually came with a vaccum gauge and has several different uses.

 

I have a Miti-vac, and I also picked up
http://www.harborfreight.com/cpi/ctaf/d ... mber=92474
on sale one day for maybe 10 or 12 bucks. but at $20, it is a fine deal.

I really need to fix a canning jar lid with hose barbs so I can have the larger container rather than the tiny cup that the vacuum pumps come with.

 

The Miti-Vac is great. It really makes bleeding brakes pretty quick work. I think the biggest benefit was that I didn't have to worry about erroneously spraying brake fluid all over the place.

 

One note of caution on using the Mity-Vac for brake bleeding: It can work TOO good and fool you.

I kept getting a nice STRONG stream of bubbles. And kept getting it. And kept getting it. Lots of nice fat bubbles. After nearly a pint of fresh fluid through the system. More bubbles. WTF???

The Mity-Vac was drawing air IN around the bleed screw threads and then INTO the bleeder through the bleed hole so it APPEARED I was still getting bubbles from the system. A couple of turns of teflon tape on the bleed screw (be careful not to block the hole, threads ONLY) and my mystery solved itself. (Thanks to a suggestion in the Mity-Vac manual who reads those?)

 

if you have better things to do with your 20 or 30 bucks, just get a wide mouth water bottle, two lengths of hose, drill appropriate holes in the lid, and suck
when your done pull out the hose, put a piece of plastic over the bottle, screw on the lid and toss it in the garbage

 

Polock
not in the garbage. Take in to recycle it.

 

Fitz, had the same problem. Never could seem to get the bubbles out but after nearly a pint I knew I must have. I would add and this come from experience that you really need to keep an eye on the level in your master cyclinder I was bleeding away down below when I thought my kid was standing over the bike sucking on a straw in an empty can. "Do over"

 

I use a 20CC syringe and a 6" length of clear hose. You can use this to push fluid UP into the caliper too (because air bubbles rise back up the lines with normal bleeding - why fight gravity?).

Costs about a buck and is hands down THE BEST way to bleed brakes (I've tried them all.....)

 

ALso it's a good idea to turn the wheel full left and full right and bleed in those positions, too, as any "air pockets" that might have formed in the high points in the caliper get exposed via that technique.......turning the wheel turns those high spots into a position that is now lower than the bleeder screw port into the caliper bore, and thus you can evacuate those spots, too (if they have trapped any air in them).

 

how big is a 20cc syringe (dah) how many would it take to do from empty?
i might give it a try

 

It takes about 30-40CC to fill your resevior, and there's probably another 30-40CC in the lines / calipers (depending on pad wear).

The real beauty of the syringe is that once you have the system full of fluid, you can empty the syringe into the caliper, them withdraw the fluid, then push it back into the caliper, then keep going as many times as you like ALL WITHOUT REMOVING THE SYRINGE. This way you'll definitely get ALL the air out

And you'll only use / waste 20cc of fluid this way :wink:

 

do you have pics of this procedure?

 

Tie the lever back to the grip & leave it overnight, don't ask me why or how.

 

tried that...did nothing. oh well, gonna try the pump, hold, crack. close, release method today. It better work.

 

did it three times and got a big bubble out on the 2nd go round. They are perfect now. Thanks fellas.

 

what a PIA. It took me 2 hours to get it bled...I didn't have a speedy bleeder tool so i improvised...

First i did the pump and bleed method...go no where.
Then i tried taking the 10 foot length of clear suction hose and taped it to the end of the shop vac and tried every position physically possible with the brake leaver to get fluid to move and no luck.

Then i took all the lines apart and blew brake cleaner through to make sure they were not plugged and they were good.

Then i took my hand pump that i use to pump up my inflatable kites and taped the 10 foot line onto it and set it up in suction mode. I took the line off the reservoir and set it in a tin of brakefluid..then i put the clear line on the bleeder valve and pumped away until i got fluid coming out and no bubbles...then i shut the valve and hooked the line back up at the top and nothing. So i opened the valve and applied suction and played with the leaver and the level would go up and down up and down...i did that for an hour and got nowhere...finally i cracked the top fitting beside the reservoir and pumped fluid through the bleed valve until it squirted out the top and closed off both ends...it got a bit better but still nothing.

Then i took and pumped the leaver a couple times and held it and loosened the line beside the reservoir and it hissed then i closed it, then i hit the leaver and it felt a bit better so i held it again and it pissed this time...did it a few more times and voila..it got better...yay...what a pia....never goin to touch the brakes again ever.

thanks for the help guys this thread was awesome

 

Good to hear you got brakes

Those bubbles in the banjoes are difficult to bleed unless you have a Mityvac or similar. Those of us without it crack open the banjoes...works a treat.

Hope you remembered to douse the spills with plenty of water :wink: