Persistant bubbles in master cylinder reservoir

[sharpeyie]

Hi all.

I replaced/upgraded the master cylinder on my Z1B to accomodate a second disc recently. New M.C. bought from Z Power. All installed but when bleeding I am still getting a handful of airbubbles being released through the small hole in the base of the reservoir each time the brake lever is released after pulling it in. There’s about half a dozen each and every time. This went on for the bones of three hours yesterday and about the same again today. Brakes are still quite soft so something still has a way to go.

Is there something I need to do to push this on a little? Am I looking at a leaking M.C or air caught in some other area of the upper brake line? I though this would have recified itself by now.

Any advice welcome.

Thank you.

Stewart

[z1bman]

tie the lever hard against the handlebar with a cable tie overnight & check your brake line connections for leaking fluid & check around the mc piston for leaks

[relisysxx]

I had the same problem with a new master cylinder from z power, I gave up and put an old single disc cylinder on as a temporary measure, will try again when I've got a bit of time.

[wilsonsjw11]

Clearing the air from the system after fitting new components is not a quick job and you need to persevere but you will get there.
Regards

[sharpeyie]

Thanks for the replies guys. I’ll keep going for a few days more .

[sharpeyie]

tie the lever hard against the handlebar with a cable tie overnight & check your brake line connections for leaking fluid & check around the mc piston for leaks

Yep, have that done ( I read that in another post somewhere on here last night.)

[kev edwards]

Don't pull the lever all the way to the bar and pull just over half way and release slowly, been using this method to get the last bits of air out for years, longest I've ever spent is around 40 minutes doing this job.

[Bill P]

I use the same method as Mr Edwards and always worked for me to

[moizeau]

I had this problem donkeys years ago. It turned out to be air trapped in the brake line splitter. If you've got one unbolt it from it's mounting and change the orientation to as close to vertical as possible then tie wrap the lever in over night.

[sharpeyie]

I’m guessing my patience is the major issue here.....

Will try those additional pointers out, thanks guys.

[pertonpc]

If you cannot get it to go hard (ooh err missus)
Isolate one side at a time (at the splitter) and bleed that. If it goes hard on one calliper but not the other you have the culprit.

[sharpeyie]

If you cannot get it to go hard (ooh err missus)
Isolate one side at a time (at the splitter) and bleed that. If it goes hard on one calliper but not the other you have the culprit.

Like it - nice one centurion!

[gray]

I agree with moizeau . there is a "high " point on the splitter that traps air. Disconnect if from the bottom yoke and turn it as far as you can clockwise so the trapped air has to rise out, no need to undo any hydraulic unions, , get something to hold it at that angle then bleed again.

[BAFF1960]

Hi.
This is a method I learnt whilst in the aviation industry. Pipe runs in aircraft are long and take a torturous routes. Back bleed from the caliper. I've used this on all my bikes with standard brake set ups [ there's been many ] and its 100% effective and only takes about 30 mins max for a twin disc set up.
Use a large syringe to feed the caliper and a small one to remove bled fluid from the reservoir. Bleed one caliper a couple of times then switch to the other. Alternate between them a couple of times more. Air likes to rise and will always head to the reservoir. If this doesn't work then the systems got a leak or suspect component.
Alan

[sharpeyie]

Thanks guys.