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
prelude2.2 wrote:Excellent Max. I hate bleeding brakes but I will have a go with this method next time i think. Thanks
It's a cinch Prelude...you will start to look forward to it!
Another handy tip I learned recently from my brother is for changing fluid: the cup of tea method.
First flick the kettle on and while that is boiling do the following:
Nearly completely drain out the brake reservoir with a syringe or paper towel (or just let it drain out of the system via the bleed nipple) but leave enough in to cover the reservoir outlet DON'T drain it dry.
Then top up with fresh fluid.
Make a brew for yourself, tea and milk is OK...and a biscuit. (we can argue about which is the best biscuit later!)
Push a drain hose and catch pot onto the bleed nipple and crack it open...now just drink a cup of tea whilst it slowly drips through using gravity.
Keep topping up the reservoir until you have finished your cuppa, Typically 2 or 3 refills will do the rear, maybe 5 or 6 for the fronts.
That's it! Fresh oil in your stoppers without any drama.
Andy wrote:I'm going to have to get you to start doing write-ups for the website revamp at this rate!
When I look for assistance on the site and I don't quite find what I need, I am happy to write up my experience, maybe it will help some other budding home tech. get out of a corner. 👍
Great write up. I use the syringe method myself, another trick I sometimes use is to crack the banjo bolt at the master cylinder and back fill the brake line from the caliper bleed nipple injecting the brake fluid with the syringe until it oozes out of the master cylinder banjo.
paul g wrote:Great write up. I use the syringe method myself, another trick I sometimes use is to crack the banjo bolt at the master cylinder and back fill the brake line from the caliper bleed nipple injecting the brake fluid with the syringe until it oozes out of the master cylinder banjo.
Cheers Paul, and thanks for the banjo tip!
I guess that is why the HEL bleed banjo would be a nice performance upgrade for not a lot of money
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I doubt there is a master cylinder out there that we can't beat now!!
Because the m/c banjo is a high point in the system, I’ve found you get a little air bubble trapped in it over time. Quite often I’d lean the bike right over to the left side when sat on it and these bubbles would make their way up the m/c and in to reservoir.
racer38 wrote:Because the m/c banjo is a high point in the system, I’ve found you get a little air bubble trapped in it over time. Quite often I’d lean the bike right over to the left side when sat on it and these bubbles would make their way up the m/c and in to reservoir.
"I'm bleeding my master cylinder officer, thats why I had my knee down honest!"
"And the wheelie was to help bleed up the rad!"
_
Lesson for us all there Racer, keep a regular service eye on your stoppers!!
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