Brake Bleed GS425 Front Caliper

[BrianH]

I'm having trouble bleeding the front caliper on my GS425. I'm not able to create significant pressure in the system to move the piston back and forth a large enough distance to create braking power.

I'm not sure what the falw in the system is.
The brake caliper piston seal is brand new. The master cyliner is brand new(although it is an ebay model) and the brake line and washers for the connections are all new and secure.

When Bleeding the brake and trying to build pressure first I fill the entire system with brake fluid from the begining of the line down to the caliper. Then I attach the line to the MC and begin pumping in fast spurts.

When the system is full of fluid I begin normal bleeding by cracking the banjo bolt, pumping and not releasing, and closing the banjo bolt. I do this until there are no bubbles visible in the clear bleed line exiting the banjo bolt.

Even after this the piston only moves minimally and there is not significant pressure in the system.

Any one have any ideas? I've searched brake bleeding on the forums and have found a lot of information, but nothing that applies to this specfic scenario.

 

[Steve]

Not a bad technique you have, just need to start a little differently.

Especially when starting dry, you need to remove the handle, then use a screwdriver to push the piston all the way to the end of its travel, while cracking the banjo open. The brake handle does not push the piston all the way in, leaving enough room for an air bubble. Pushing the piston all the way with the screwdriver will get rid of that bubble, too. Then you can resume your "open, squeeze, close, release" technique to push fluid through the system.

.

 

[Steve314159]

And bleed the master cylinder as per Chef

"take off the line from the M/C to the junction box and dunk it in the resevoir. With the brake lever off push in the piston with a philip screwdriver until the little bubbles stop."

Except I'm not sure I did it exactly that way. I disconnected the line at the junction box, dunked the end in the resevoir, and pumped the handle until the bubbles stopped.

Worked for me yesterday.

 

[BrianH]

The junction Box is where the line connects to the MC? Correct?

At that point do you run some kind of clear line off the MC to see if bubbles are coming out?

 

[lfisher]

Try Speed Bleeders

Try Speed Bleeders

Save yourself time and anxiety - Try some speed bleeders. You can get them directly from the manuafacturer or from resellers. They work well and you can do 'em yourself without all the muss and fuss. I have them on my GS1000 Racebike and had them on my HD as well.


Leo

 

[teddux]

Try "back-bleeding"

 

[doug g]

I have been dealing with the same issue on my 550es. been driving me nuts. I will try the suggestion above of removing the line from the junction and bleeding the mc until i see no more bubbles, i will be sure to try the screwdriver method too.

 

[Nessism]

The system needs to be primed before it will pump with the lever. Easiest thing to do is draw a vacuum on the caliper nipple to pull fluid out of the reservoir and prime the system.

 

[Steve]

That usually works, unless there is an air bubble caught in the master cylinder.

Using a screwdriver to push all the way in on the piston usually takes care of that.

.

 

[Guest]

If you have ever bought a car M/C it comes with two plastic pieces that screw into the line threads and hoses. These are to bleed the M/C. You put the hoses directly into the brake fluid of the reservoir and pump the brake pedal until the bubbles stop.
The advice I gave does this. If there is air in the M/C you will never get the brakes to pump up properly.