Topic: Bleeding brakes with a modern master cyclinder..

[ieism]

I put a new Brembo master cylinder on my 550, it has dual disks and I didn't like the stock MC.
Now, I've bled brakes before but I can't get this one anywhere near firm.
There are no bubbles coming up in the resevoir either, but lots of bubbles from the bleed nipple on the caliper.
The MC is new, it's the right size too. All the brakelines are tight and not leaking.
I've been pumping brakefluid trough it for nearly an hour and a half, it's driving me insane.
I needed 3 beers before I could compose myself enough to write this...

Ivar

[ieism]

Ok, I solved it myself. And it only took me 4 hours

There was air in the top of the system because my resevoir wasn't the highest point in the system. So if you're having trouble bleeding a bike with low clip-ons, try taking the MC of the clip-ons and raising them so the air can rise to the top.
Stupid, but I did not think of that yesterday.

[Vtec-Sauce]

try pumping up the brakes really good with the brake lever then using rubber bands or a clamp to keep the lever pulled in, remove the reservoir and leave it sit over night, did this on dirt bikes and atv's and it works great, lets all the air bubbles rise out overnight.

[c_kyle]

What kind of Brembo MC did you use/where did you get it?

[ieism]

I used one of an Husqvarna supermoto bike. These have huge double-piston brakes, but with a single disk.
I figured this would be close enough, as my 550 has two pistons too that looked pretty close in size.

I bought it secondhand.
The MC is very good quality and the lever feels great now. The engine is being rebuild now, so I'll have to wait how good it brakes.
I also upgraded to steel brakelines.

Another option would be a Grimeca MC. These are still made new and are available in different sizes.
They cost about 100 Euro, and I've been told 16 to 18mm works great with double disks.

[WJL75]

I had the same issue with my new MC with clipons.  Found the same solution you did...only wich I could have save you some time by reading the post earlier.  Big improvment with the new MC.

[c_kyle]

Thanks for the info.

[lordmoonpie]

It works the other way up too - put the MC lower than the bleed nipple, cable tie the lever at the pulled in position to the bar (obviously you take the bar off too and leave overnight. Works a treat.

I do this for my race VTRs and you can barely move the lever when the brakes are cold, awesome!

[KB02]

Another trick that I have used with success is Reverse Bleeding. Basically the same principle, it's just that your putting the fluid in from the caliper and waiting until the air is pushed up from the bottom rather then pushing it down from the top.