Bleeding brakes after full system rebiuld.
 

G'day guys.

I am having a problem bleeding my brakes after a full strip down and rebuild of the system (standard apart from braided lines). This means not a drop of brake fliud in the system to start with. I am using a brake bleeding tool however it is not a vacuum tool, just a one way valve to stop air going back up.

I have had no problem with the clutch or rear brake or anything else over the years. I have bled the master cylinder and the lines until all the air is out of them, and the bleed line is clear, however lever feel is terrible and the lever can be compressed back to the hand grip. I left the lever tied back to the bar overnight and when I cracked the bleed nipple again a couple of bubbles of air came out. I have done this a couple of days in a row now.

This leads me to believe that air may be caught in the caliper, and is coming up slowly when the system is left compressed. Any thoughts on this guys, and is there an easy way to bleed them? Is a vacuum bleeder the way to go?

Cheers,
Shayne

Well, you tried one of my tricks already - to tie the lever back to the bar overnight. You may want to get a vacuum bleeder kit and try that if you still have a problem. I figure you made sure all the connections were tight and if they were loose you should have seen a leak. Did you bench bleed the master cylinder? I know on cars they always recommend it when replacing one and usually include the hoses to do so. Good luck with it.

Thanks Rick.

Yeah I have tried all the tricks I know. I bled the cylinder first and then the banjo on each caliper before I started the serious stuff. The thing is you can put as much fluid as you want through each side and the bleed line will not show a single bubble. But the lever is spongy. Then when you tie the lever back overnight, the next day you can get a couple of bubbles out. This si progressively making it better but I have been doing it for 4 days so far and it is still a lomg way off being right.

You guys that have changed calipers to GSXR or 954 etc, did you have this trouble?

Help!

Hi Shayne,

I was obligated to bleed the brake when I do my front end swap and it was one of the hardest part of the project until I find a good way to do it!! Even if I've bought a little tool on ebay ( like this http://cgi.ebay.ca/Special-Automatic...QQcmdZViewItem ) I've found that it's useless when it come to bleed the master cylinder!!

I've just do it again last weekend; I replaced the brake master cylinder of the girlfriend F4 with the CBR1000RR that I was not able to install on the VTR, I also installed her some 954 calipers ( even if they seem to be almost same as stock F4 unlesss the color)! She is very happy now, by the way!

So, here is the trick, I used a pair of long nose Vise-grip ( I know, I know dummies tools!! ) to pinch the rubber hose 1 inche the master cylinder. After the hose was pinched, I pumped the lever when losing the hose screw at the master cylinder head to let the air goes out ( and some oil also, be gentle with the pressure). I do this only a few time and I fell the lever become more hard, that means I got pressure now on the master! After, I grab the Vise-grip in hand and I loosed them "a bit" while pumping the lever with at each turn the bleeder open on one caliper, it took almost a full brake cup of oil, but I worked!! ( you could let the brake reservoir open while doing this, no problem, it's easier to refill and it doesn't change anything else )! After you have do both calipers like this, you should have been done! My .02!

On the other hand, I'm still confuse because I'm looking to replace my rubber hose by some SS line and I really don't know what I will do to bleed the brake with these new SS line!? Because I guess it won't be an option to pinch the line!!? I will figure this later, unless some of you guys have another trick!? :?:

Thus, is you still have rubber line Shayne, try this "Noob tool" trick, it worked very well for me two times. :)

Hope it will help

Cia and GL

Thanks Icebud. Bleeding the master cyclinder first as you have done is always a good idea. You can do the same thing withot using the vise grip though, as gravity and a little lever pressure will get fluid through the banjo fitting without crimping the line. Simply loosen it off enough for the fluid to flow and you will be right.

In my case it is not the master cyclinder that is the problem, it is the calipers that appear to be retaining the air.

Any ideas guys? I know a lot of you have changed calipers. Anyone had this problem?

I'm old school do it by hand it always works check other thread for how to.

repost from another thread
here's my tips for final bleeding
PATIENCE IS KEY!!!! tiny bubbles need time to float up to the highest point of the brake system...

if you have brake pressure, place the bike on the sidestand and turn the handle bars all the way to the left to assure the master cylinder is at it's highest point... stand next to the bike and just flick the tip of the lever so that your jarring the fluid in the entire system... each of the banjo bolts, any joints, the calipers have tons of area for the bubbles to hide while your doing this, have the master cylinder resoivor (sp?) cap off so you can see the little bubbles flowing up. this jarring of the suspension fluid will knock trapped bubbles free and help them rise to the master cylinder, i can spend 10 minutes or more doing this and seeing bubbles still rise up to the resivoir.. i also do a squeeze and release, like releasing an arrow from a bow, squeeze the lever and let your fingers slide off it so it flicks itself out... the fluid will compress, then any trapped air will force itself and fluid back into the master cylinder... this also takes time, do it ALOT and be patient...

another thing i do is using a thin pry bar or tire iron, VERY GENTLY TO NOT BEND THE ROTOR pry the pads back into the caliper (this can be done with the calipers removed... keep the banjo bolt inlet to the hose at the highest point so any trapped bubbles will be forced up) keep an eye on your fluid level so you don't get any on the painted parts.. this forces fluid back UP the system to the highest point, taking any trapped air with it.. walk away from the bike, grab a beer, smoke, poweraide, whatever, and let the air have some time to float to the uppermost point... if you immediately pump the system back up your just pumping the bubbles back down...

mitivacs work well for initial priming of the brakes, but patience and these tricks should improve your stopping performance...

any other ???'s let me know... (i'm a MMI grad with HONTECH and own my own shop)

Some good tips there Johhny, I will give them a go when I get a chance. As you can see from my posts elsewhere, I have been using lever pressure, but not in the manner you suggest. No bubbles have been seen in the reservoir for a week now. The only air bubbles are coming out of the bleeder, after one pump of the lever, then no more, so the air is low in the system.

I will give the caliper trick a go too. When I first assembled the system the pistons were fully in, and once the system was bled (or I thought it was) it took ages for me to pump those pistons out to touch the rotor, and I knew there was a problem straight away.

I appreciate your help here, as I was running out of ideas!

something i forgot to mention.... remove the bleeders from the caliper and wrap teflon tape around the threads to seal them while your bleeding, be careful not to cover the holes in the side of the point... when using a mitivac you'll actually suck air through the threads and into the hose and it'll look like you're still pulling air out, when it's only passing thru the threads.

another tip, loosen both caliper bolts, remove the lower bolt, rotate the caliper backward untill it just about touches the rim and retighten the upper bolt snug to hold it in position... the bleeder passage is not quite at the top of the brake body, and rotating the caliper back will locate it to the highest point... you'll want to insert some sort of tire iron or flat piece of metal the same thickness as the rotor so the pads dont get deformed when your pressurizing the brakes... now turn the handlebars so the caliper your working on is facing forward so the bleeder is at the uppermost point.. should help release bubbles...

Righto Jonny will do that. It is getting better slowly so we are on the right track.

Righto, well I have gone down to the local Honda dealer and checked out some brakes on the new bikes in the showroom, and mine feels about the same as a new Fireblade (CBR 1000) so that will do I guess!

The end result is that none of the tricks that you guys gave me did anything special. The only one that had an effect was to tie the lever back overnight and then bleed again. Weird, I can't explain it.

Something to remember for next time. Thanks for all the tips guys.

Cheers,
Shayne