Brake bleeding

[Barry]

Just did my 2 yearly change of brake fluid.

Last time when filling the system after a full strip down I pumped the fluid in from the bottom through the bleed nipple with a large syringe which displaces all the air upwards and seems to work pretty well but still needed the lever tying back over night to firm it up.

This time for just a fluid change I thought I'd try using the same syringe to suck the old fluid out the bottom. I think you can buy vacuum bleeders which work on the same principle.  This also worked pretty well although still left me with a softish lever. Beats me where the air managed to get in but tying back the lever made it rock solid again.

Same technique of vacuum bleeding also worked on the car as did firming up the pedal by wedging it down

[crocket]

Made a bleed kit for mine after struggling. It consists ofa 6mm alloy plate and matching rubber gasket with a Shreider tyre valve fitted to the centre. It is drilled to replace the top of master cylinder.I used a bike pump to pressurise slightly then keep bleeding/pressurising. Worked for mine.Be careful not to over "inflate"!

[Barry]

Be careful not to over "inflate"!  

Sounds like that might be the "voice of experience"  

Nice idea though our master cylinder reservoir with the threaded bosses could have been made for it.

For bleeding the brakes on a car I once made up something similar with a 5 litre garden sprayer as the air pressure reservoir. Worked a treat until I over pressurised it spraying brake fluid everywhere.

[raymr]

I have a Topsider vacuum siphon for doing oil changes. It's also handy for sucking the old brake fluid out of the reservoir. Then I fill the reservoir with new fluid and attach the suction tube to the brake bleeder. I crack it open and suck the brake fluid through while topping off the reservoir.  

[VaSteve]

I'm a little confused on tying the lever back.   What did that do?   Let the rest of t he air out t he top?   Does that work even if the bleeder valve is open at the bottom?  


I'm having a hell of a time bleeding mine after a master cylinder swap.  

TIA

[Bob_Roller]

What method of bleeding are you using ?

If you are using the vacuum bleeder, put one wrap of teflon tape, on the threads only, so it doesn't interfer with the sealing of the bleed screw .

You are drawing air from around the bleeder screw threads, so it looks like you still have air it the system .

I think this can happen when you use the 'old' method of holding the lever in while opening the bleeder screw .

With the bleeder screw fully seated, wrap a rubber band around the brake lever and leave it for a day or two .

[Barry]

I'm a little confused on tying the lever back. What did that do? Let the rest of t he air out t he top? Does that work even if the bleeder valve is open at the bottom?

That's a good question. It lets the air out somehow and works every time in my experience but not with the bleed screw open. You only do it after normal bleeding to really get the last bit of firming up on the lever.

I'm having a hell of a time bleeding mine after a master cylinder swap.  

As Bob said the old method of bleeding doesn't seem to work that well for me either. Using a vacuum bleeder or a syringe on the bleed screw worked so much better I changed the fluid in 10 mins flat followed by the lever tied back over night.

[VaSteve]

I have been using the gravity method...and the squeeze the lever and crack the bleeder method.   I have bled brakes a thousand times on my car but I have a Motive pressure bleeder.   I guess I can get one of those vacuum bleeders at the auto parts store?  

[Barry]

I guess I can get one of those vacuum bleeders at the auto parts store?  

Yes or a lower cost version - just a large syringe and some small bore flexible tubing both of which will come in handy for other things too like adding fork fluid. Beware of cross contamination though as the smallest trace of oil can contaminate brake fluid and cause problems with the seals.

When using a vacuum bleeder of any sort it's best to crack the bleed nipple open by just the smallest amount needed to get the fluid flowing or air will tend to be drawn in around the threads.

In the first part of brake bleeding. You can sometimes get air out just by squeezing the lever slowly. With the reservoir top off you should see tiny bubbles rise but you do have to squeeze slowly or a pulse of fluid will try to make an escape bid and land on your paintwork.

[Bob_Roller]

If you have a Harbor Freight Tool store near you, you can usually get one for around $20US, maybe a bit less, if you happen to have one of their 20% off coupons .

http://www.harborfreight.com/automotive-motorcycle/brakes/brake-bleeder-and-vacuum-pump-kit-92474.html

[Barry]

Very similar looking if not identical vacuum bleeder kit available in the UK.

http://www.vehicletools.co.uk/sealey-vs402-vacuum-tester-6649-108486?utm#

[Bob_Roller]

Made with 'pride', in China !!!!!!!

[jaap43]

I'm a little confused on tying the lever back. What did that do? Let the rest of t he air out the top? Does that work even if the bleeder valve is open at the bottom?

That's a good question. It lets the air out somehow and works every time in my experience but not with the bleed screw open. You only do it after normal bleeding to really get the last bit of firming up on the lever.

Bracking fluid can not be compressed, but air do it. If you set pressure on the system the airbubbles become smaller en can rise easier to the top of the system.

[nhmaf]

I just changed the fluid in the front brake on my 78 R100 (with the under the tank master cylinder).   What a PITA that can be..  I've even lost my trusty check valve/brake bleeder, so I had to resort to the old method.   Well, at least it appears that I'll be able to stop as well as that swinging ATE gizmo will allow..  makes me really appreciate the dual Brembos on the R65LS!