Nissin front master cylinder - bleeding the blighter! (and the rear too, maybe…)

Not an easy task if you have had this all apart and it is all dry, but I made a handy hack.

I think the air in the MC gets trapped due to the angle it is located at on the clip-on, so if it does not bleed up conventionally after three or four attempts you may as well give up, you will just pump litres if clean fluid through for no gain.

You could try this:
Get yourself a big syringe (without the needle!), the one I use is 60ml, and some 5mm clear PVC pipe (battery breather hose is handy if you have some).
Stick the pipe on the syringe as a push fit, if it does not fit tight use a zip tie to lock it in place.
Wrap a small "towel" of paper towel around the caliper nipple.
Assuming you have nice clean fluid in the system, draw up about 30mm of fluid into the syringe pipe from the MC reservoir.
Now go to the caliper and holding the syringe lower then the end of the pipe, push the pipe onto the bleed nipple on the brake caliper. You do this so no fluid drips all over the place.
Now lift the syringe up until the brake fluid inside runs down the pipe to the nipple…now you have no air in the pipe.
Crack the bleed nipple open and draw back on the syringe to effectively suck the fluid through the system…check out all that air! It is like drawing up a beer!
Don’t operate the brake lever as this will shut the system.
Close the bleed nipple each time you stop to empty.

Do this three or four times each side emptying the syringe back into the master cylinder each time. Empty the syringe slowly or it will go everywhere, you are not inseminating cows!!

DO NOT let the master cylinder run dry or you’ll have to start all over again.

You will keep seeing air, it will constantly do this although the system has been purged, I think it leaks into the pipe from around the nipple thread or something. But after 3 or 4 attempts each side you should now be getting some feeling at the lever.
When you have the lever back you can start to bleed conventionally.

Check your brakes and the work you have done, torque values, thread lock, take all the safety precautions.... and double check them before riding.

And not a drop has been spilled.

Now relax with a beer, smiling smugly in the knowledge that the dreaded Nissin master cylinder is now your slave!


Last edited by Max on Tue Jun 16, 2020 1:29 pm; edited 1 time in total