Can anyone give me advice on bleeding brakes.
I am setting up a master cylinder of 11mm piston diameter on the front end of my 850, which is running with an RGM big disc and Grimeca twin pot caliper.
I have pumped the piston and connected a tube to the bleed nipple at the caliper, running down into a glass jar with some fluid in. The tube fills with brake fluid up to the point where it turns downwards towards the glass jar, when I pump it just runs away down towards the jar. The system still allows the lever to touch the bars without too much resistance.
Has anyone got a good method of bleeding I don't know about. I always seem to struggle here...
Stu

Pump the brake with the bleeder valve closed. Then hold the brake on and crack the bleeder valve. If air bubles escape, close the bleeder and release the brake handle. Pump again and repeat until no bubbles escape when you crack the bleeder. If you still have no brake or a spongy feel, you can remove the master cylinder from the handlebar and raise it until there is no bend in the fluid line and pump again. Be careful not to spill brake fluid on the paint! Sometimes getting that last bit of air out of the line can be frustrating.

Some people prefer an "up bleed" method. Using a plastic syringe filled with brake fluid, inject it into the caliper bleed nipple slowly and force the fluid (and bubbles) up toward the MC.

maylar wrote:Some people prefer an "up bleed" method. Using a plastic syringe filled with brake fluid, inject it into the caliper bleed nipple slowly and force the fluid (and bubbles) up toward the MC.

This is how I've done it for years on mountain bikes with disc brakes. It works well.

Syringes are a great tool to have around, especially for bleeding brakes, measuring and injecting fork oil ect.

The hand-operated brake bleeding pump kits are invaluable.

You can use both the pressure and vacuum features to ensure ultimate success.

Some people prefer an "up bleed" method. Using a plastic syringe filled with brake fluid, inject it into the caliper bleed nipple slowly and force the fluid (and bubbles) up toward the MC.

When using this method make certain that you have a tight sealing hose on the end of the syringe and teflon or other sealer on the threads of the bleed nipple. Don't use too much pressure or you can blow the tubing off the syringe or bleeder making quite a mess. DAMHIK!!

I made a power bleeder from a small weed sprayer. It does need a master cylinder reservoir cover with a hose nipple. It worked great on the BMW ABS brake. In fact, they must be bleed that way. I've yet to try it on my 11mm master and Grimeca 2P caliper for my Norton.

JimC
I got an 1mm master cyl for £10 off a mate..as you suggested...think its a Lockheed...it says 'ap' on it..this is what I am trying to sort.
Handle still pulls back to the bars so far....
Stu

I assume you meant 11mm. You stated you are using a Grimeca 2P caliper. This will work great. I have that exact same setup. You may have air in the line. If not, maybe the £10 master cylinder needs some work. If the seal is shot the lever will go to the handlebar without building any pressure.

11mm yes.
I can't see any leaks, it must be air in there but I can't seem to get rid of it. Must have pushed half a can of dot4 through it last night..
Stu

You won't see any leak if the m/c seal is shot. Fluid will pass by it, but still be contained within the m/c.

JimC
Bugger, coz I don't know what the thing is to buy spares.
If I blank off the line to the caliper it should be hard as a rock if good and still soft if bad....yes?
Stu

bigstu wrote: Bugger, coz I don't know what the thing is to buy spares.

List of UK AP parts distributors: http://www.apracing.com/info/distributor.asp (Andover Norton is one)

bigstu wrote:If I blank off the line to the caliper it should be hard as a rock if good and still soft if bad....yes?

= Yes, depending on where you blank it off? If air is still trapped between the master cylinder and wherever you blank it, then could still be the same?

You could try tying the brake lever back against the handlebar and leaving it overnight ? This seems to work for many people.

Try cracking open the banjo bolt that holds the brake line to the m/cyl while squeezing the brake lever(cover all paintwork 1st!) because if the bolt end of the cyl is higher than the hole in the reservoir the air can't escape.

hi bigstu,you mentioned everything but the flexible rubber hose,i had a similar problem and it turned out to be the hose had collapsed inside