Front Brake XR400

[kiwijohn]

My front brake has become quite spongey. With the lever pulled in the wheel does not lock. I can push the bike with the front brake fully on.

My mechanic has bleed the brake lines. The fluid is correct. I have changed the front pads; still no improvement.

What is next? A new disc, new lines, caliper overhaul?

Has anyone else had this happen?

[AlanH]

It may be that the master cylinder seals are failing. This can cause a loss of braking pressure without fluid leak. If it was caliper seals causing this much of a loss in pressure, you'd see fluid leaking. Aftermarket master cylinder rebuild kits are available that are cheaper than Honda spares - although I generally go for genuine on master cylinders.

[jasonbc]

My front brake has become quite spongey. With the lever pulled in the wheel does not lock. I can push the bike with the front brake fully on.

My mechanic has bleed the brake lines. The fluid is correct. I have changed the front pads; still no improvement.

What is next? A new disc, new lines, caliper overhaul?

Has anyone else had this happen?

If you take the top off the master cylinder and pump the lever you should see small bubbles rising up through the fluid as you pull the lever in. If you don't chances are the cyclinder is going tits up

[AlanH]

They only bubble if you've not bled all the air out properly or your bike's been upside down recently A lack of bubbles isn't a trusted sign that the cylinder is knackered. My newly rebuilt and bled one doesn't make any bubbles at all and that is absolutely spot on.

[catteeclan]

Still got rubber brake pipes?
Clamp a little after the master cylinder and test? Still crap, the m/cylinders at fault. If it lever travel is better clamp at the caliper end, crap again them change you pipes, if good then your prob is on/in the caliper.
Doesn't fix the prob but it'll get you closer to it.

[kiwijohn]

Thanks for the advice...