Endless air bubbles.

[roverfj1200]

Rebuilt my front callipers today and after fitting I seem to have a endless flow of bubbles as I try to bleed them..

I will have another go in the morning and see how things go..


Cheers

[chiz]

Try pulling in the leaver and leave it over night with a wrap of tape to keep it puled. Also get an old brake hose and cut off the bit at the end where the banjo bolt passes through into the caliper. Close up the bit of steel brake line with weld or solder. Then run a banjo bolt through this at your handlebar master and tighten down tight with the copper washers.
   Now you have your brake cylinder dead ended with this little device now squeeze the crap out of the lever to try to expell air from your master.

[Pat Conlon]

I found when using my MityVac, air bubbles, but a wrap of teflon tape on the bleeder port threads solved that issue.

Also, make sure you use fresh crush washers. They work harden from compression and if you don't have new washers available your old one's can be re softened with a butane torch.
Thank you LA Mike for this tip....

[~JM~]

I zip-tie the lever back 50% & let it set overnight. That allows all the small bubbles to migrate to the top of the reservoir.

[ELIMINATOR]

I found that flicking the brake lines with a finger, releases a lot of bubbles.

[fjfool]

I zip-tie the lever back 50% & let it set overnight. That allows all the small bubbles to migrate to the top of the reservoir.

i just posted this in another thread:



"When the bike has been resting for several hours any tiny air bubbles in the brake lines will have risen to the highest point that they can. When you then apply the brakes you push those tiny bubbles back down along with the brake fluid, and when you release the brakes they rise back up with the brake fluid but never move higher in the system. To get the air out you need to move those tiny air bubbles higher.

When you clamp the brake lever down overnight the tiny air bubbles move down with the brake fluid as usual, but then get many hours to rise back up to the highest spot. If the highest spot is directly below the master cylinder then the air bubbles will get sucked up and out of the system when the brake lever is released. Air bubbles further down in the system will also move up past where they could before, allowing them to rise to a new high point and to eventually be bled out by repeated application of this technique."

i have never had to "repeat" this method but, after reading this, it might be worth trying this 3or4 times
good luck
-also, bleed the system at the banjo thats on the master cylinder, use a rag or something to catch the brake fluid before it starts removing paint

[Earl Svorks]

 If your master cylinder is working and adjusted properly, (meaning there's a bit of clearance between the piston and the lever) there's no point in holding the lever in as you are trying to bleed the brake. If you look in the reservoir you will see two holes in the floor. Yamaha kindly provides a little metal cover over the smaller hole. This is the compensating port. When the lever is relaxed, this port opens the cylinder bore  to the reservoir. This allows brake fluid to return from the caliper. It must be open if fluid and or air is to re-enter the reservoir. The first thing that happens when you squeeze the lever is that the primary cup on the piston closes this port after a very small amount of travel. That little metal cover serves to prevent the brake fluid from hitting you in the eye as it squirts out of the bore, through the compensating port. Air will happily come out through that port if it's open, providing it is the highest point in the system. Turn the bars, lean the bike, move the master, whatever it takes. Most hard luck in bleeding is the result of the "C" port not being open when the lever is at rest. When you bench bleed the master, with your finger over the 10mm discharge port, as you squeeze the lever, fluid will come out under however much pressure you care to exert,,, now,, when you release the lever, holding the port closed fluid should be pulled into the main feed port (the bigger hole in the floor of reservoir) to replace what has been pumped out. You should not feel suction (or very little) on your finger. If you do, when the lever is relaxed this means the "C" port is not opening. This is when that little bit of free play is all important.If you're not sure about this, you can apply a little air pressure to the discharge port (you have drained the master first). This pressure should easily escape out through the compensating port. If it doesn't , you must discover the cause before attempting to bleed the system. Look for crap behind the snap ring under the boot at the outside end of the bore, swollen primary or secondary cup.
  Sorry for the length of this, but someone had to say it.
  Cheers
Simon

[ribbert]

Sorry for the length of this, but someone had to say it.
  Cheers
Simon

They have, many times. Maybe they'll listen to you, I gave up a long time ago.

Noel

[FJ_Hooligan]

It's not the position of the lever, it's the "leave it overnight" part that's the most significant.  :-)

I did a full front caliper rebuild this summer and never touched a bleeder.  Took a couple of hours, but ALL the bubbles came up through the master.  Most of the time was spent doing something else while the fluid worked it's way down and the bubbles up.

[Tony Mac]

Rebuilt my front callipers today and after fitting I seem to have a endless flow of bubbles as I try to bleed them..
I will have another go in the morning and see how things go..
Cheers

Hi Richard, I am having to rebuild my callipers as well, and I'm not looking forward to it.
Did you replace everything?
If so where did you get the bits.
I have found a complete rebuild kit in the UK but I would rather buy from here quickly.
Be Good.
Tony Mac

[roverfj1200]

Tony

I use this Ozzie supplier or you could order from Randy. I only replaced the rubbers and O rings. My old callipers where so warn out I think the pistons where grabbing so even after the rebuild they where still SHIT.

A move to the blue dots is sooooooo worth the cost...

http://yamaha-parts.victordrummond.net/


Cheers.

[ribbert]

I am having to rebuild my callipers as well, and I'm not looking forward to it.

Tony Mac

Tony, nothing to worry about, a piston and a seal, that's it.
Why do they need rebuilding anyway?

Noel

[Burns]

This is a question rather than a suggestion, but if you loosen the banjo at the M/C and let the bike sit awhile won't all the air below the M/C migrate up and out to atmosphere? Would that leave a bubble in the system?

[Pat Conlon]

You will still have air in the system, besides don't need to do that...If your master cylinder is clean (pull out the plate and look at the bottom of the reservoir) and the relief port is open (aka: C port), the air bubbles will exit the system and bubble into the reservoir....eventually.
If you are in a hurry, you can do 2 things;
1) Do a reverse bleed. Inject fluid with a syringe at the caliper/slave and push the air up towards the m/c. Be careful that fluid can squirt.
2) Use a vacuum pump (MityVac) at the bleeder port and pull the fluid quickly down from the m/c.

^^^ Earl, Noel and Hooligan are spot on. The secret in getting any small amount of remaining air out, is being sure the m/c relief port is open, unobstructed and let time and gravity do its work on the bubbles.

[mark1969]

I have just done the 'tie brake lever back' for 24 hrs+ and it definitely works. It's important to let the air come out through the master cylinder, so leave the lid propped up a little with some room for air to escape.

I used a cable tie to hold the brake lever and also helped the bleed along by letting some air out through the banjo bolt that goes into master cylinder. Quite a lot of air came out there and I left the lever tied back for a few days in the end. All is good now with a firm lever.

Basically, it works.