Hi All,


Does anyone know of any rebuild kits for front MC?
My still seems spongy after bleeding.



Thanks in advance.

There is probably still a small amount of air in your system. It only takes one little bubble to give a spongy feel.

Were your Master Cylinder seals leaking by, you would slowly lose pressure as you held the brake lever taught.

Some things to try:

Bleed at the upper banjo connection by cracking it slightly open, applying lever pressure carefully, tightening the connection, then releasing pressure.

With the reservoir cap off, "tap" the brake lever in very short staccato bursts and look for bubbles to release into the fluid. (This is a small motion)

Remove the calipers and push the pistons all the way into the caliper. Block them in place. Bleed the calipers while elevating them. Reinstall.

Does your bike have ABS?

Put a banjo with a bleeder in at the reservoir point, it just makes it easier.

Get a pneumatic vacuum bleeder as well.

If you have ABS, as hinted by SilentService asking, the procedure is a little more involved.

Thanks for the replies.
None ABS model.
I do use a vacuum bleeder hooked to a compressor.

The lever has always been somewhat spongy when i bought it.
Even after using half a bottle of fluids still not a big improvement.

Your air pressure may be too high. When using a pneumatic vacuum bleeder air pressure should be around 60 psi. More than 90 will cause problems.
High pressure moves the fluid so fast that wall friction creates turbulence. That turbulence introduces very tiny air bubbles into the fluid. Once the bike sits over a short period those very tiny bubbles coalesce into larger bubbles and the lever gets soft again.


Another tip is to let the bike sit at least overnight and then remove the reservoir cap, lower the fluid level, then push the caliper pistons back in their bores.
This moves the fluid up into the reservoir, and along with it any air bubbles.....which will naturally migrate upward as the bike sits.

Then pump the lever slowly to push the calipers back out and finally top off the reservoir.

Chuck's tip about lightly tapping the lever (staccato pressure) also helps get those tiny bubbles to float out into the reservoir.

I haven't been able to locate a rebuild kit. Not sure which Nissin email to use to ask about repairs.

Time to upgrade the master cylinder to Brembo or Magura or ISR or ...?

Brembo 19RCS works well. Never rated the original Nissin, always needed bleeding and not powerful. You may need a longer brake line and the banjo bolt is a different pitch thread. You will need a Brembo micro switch for the brake light and cut and solder the wires from the switch block. Most important consideration is the mirror mounting. Brembo do threaded clamps but the std. mirror just doesn't look or sit right. Bar ends or something like std. Yamaha MT-09, Rizoma mirrors. Not much room for mirror clamps on the bars, not enough room.

Cheers

Deano

I have had more problems than not with a vacuum bleeder.
Bleed your brakes the conventional way by connecting clear plastic tubing from the brake bleeder to a container half full of water or brake fluid.
Compress the lever.Open and shut the bleeder valve,then release the lever.
Do this 6 times on each caliper,starting with the R/H caliper first.
See how you go.

Thanks all for the great tips.
I did clamp the lever open over night, that has helped abit i think (lost all reference point after all the squeezing)

I'll take the calipers off and do a deep clean and look at the pistons, good to check those anyways.
Lever has abit of travel before good strong pressure, bike has over 5000km on it so maybe just worn pads also.

Wish me luck.