Misc: Everything Else Problem Reverse Bleeding Disc Brakes

[CarlHungness]

I have a 5/8" Yamaha master cylinder feeding a pair of Kawasaki calipers on my Shadow. I have tried to reverse bleed the system, pumping fluid up to the master cylinder as opposed to using the bleeder valves down below. I can't get the fluid to run up, I get back pressure. Conversely when I try the conventional method I get 'some' fluid coming out of the bleeders, but I would have thought I'd be able to get a full stream leading into my catch bottle. I can't get the fluid to flow that far at all, I get about an inch of fluid in the catch line and no more.
I am trying to change the fluid in the system, I went too long before doing so and the brakes we working at a highly lessened level. I sucked the fluid out of the reservoir, replace it and tried again to flush from top down with minor luck. Then from bottom up, with no luck.
I'm familiar with the method of cracking open the bleeder, pulling the brake handle, then closing the bleeder before letting off the handle.
I know I've replaced a goodly amount, if not all of the fluid in the calipers and lines through my top down method, but looking for suggestions.
I have a double banjo at the master cylinder and have heard they do hold a lot of air. I spent a very long time pumping the handle, looking for minute bubbles to rise, and then doing it again and again.
Wondering why I can't bleed from bottom up and why I can't get a full flush from top down.
Years ago when I installed the system the advice (on the inst. sheets) was to use Dot 3, which I did, and have come to realize
I would have been better off with Dot 4 or 5. Thus I wanted to change the fluid completely without removing everything from the system,
but afraid I have some Dot 3 left, so that's what I flushed with, and refilled.

 

[bmetcalf]

Dismantle, clean with brakleen, use new gaskets, try again. Make sure caliper bleeders are above inlets.

 

[Cyborg]

Are you sure the piston in the master cylinder is returning far enough to open the port? Is the port blocked with crusties? Brake lever/master cylinder mismatch?

 

[Alyson]

I've had a similar problem on my BMW R100CS with dual front disc brakes and a master cylinder at the handle bar. My hydraulic hoses were shot. I replaced them with new aftermarket ones and they never worked better. Use a good quality brake fluid as per manufactures instructions. Usually the D.O.T. rating is on the master cyl. cap. I bleed mine right wheel first, then left. I usually replace fluid every two years. My bike is parked inside. I talked with a Harley mech. and I was told they never bleed the front brakes unless there is a problem. Yikes. I cleaned out a master cylinder on my friends Harley. It looked like black mud inside. About an hour later she was on the road again. If you can squeeze the brake lever and nothing comes out the bleeder, then something is blocked. Hope this helps, Alyson

 

[CarlHungness]

Dismantle, clean with brakleen, use new gaskets, try again. Make sure caliper bleeders are above inlets.

The bleeders are on the bottom, inlet on top of the caliper. So are you saying take them off, turn upside
down? I've seen lots of YouTube whereby they just plug into the bottom of the caliper at the bleeder and
are able to pump fluid back up to the master cyl. Maybe I should dis-mantle the whole system, something
may be plugged.

 

[Russell Kemp]

Carl, you could try this https://www.ebay.co.uk/itm/144811122629. I have used one to change the fluid on a number of bikes/cars including the CBR600 setup that was on my Shadow. I am sure you can get the same thing in the USA.

Russ

 

[oexing]

We got not a single vehicle at home with glykol brake fluid. Instead all silicon brake fluids DOT 5 , even in the Jag E-type since 30 years, never changed. Silicon does not attract water so no rust anywhere and no blocked hoses. Best you disassemble the lot and get new seals in all places - the last job you´d have to do for decades.

Vic

 

[passenger0_0]

Almost certainly the brake master cylinder piston is not returning enough for the front seal to clear and open the small recuperation port.
Suggest you first check there is free-play between the lever and piston.
If no clearance, or this port is blocked in any way, this situation could get dangerous when the fluid gets heated, causing expansion and locking of the front brake.
I strongly recommend you get someone who knows what they are doing to sort this problem out.

 

[BigEd]

Dear Carl,
I assume your system is very similar to mine except that I have separate lines to the callipers as that is what I had available when I did the initial installation. I have not, as yet, got around to installing a manifold to tidy up the installation at the master cylinder end. I did not have a problem bleeding the brakes from the top down. As others have said you may have a problem at the master cylinder end, clean and check for full movement. You may see a bubble appear from the bottom of the master cylinder when you operate it.
Although you should use a recommended type of brake fluid a non-recommended type will not stop you from bleeding your brakes.

 

[Normski]

I use a large syringe and a length of windscreen washer pipe to bleed brakes. Rather than reverse bleed I always use this to suck fluid through. Put tube onto nipple, crack nipple open whilst pulling plunger then close nipple before plunger comes out of syringe! Empty syringe into pot and repeat as necessary moving around nipples and calipers. This has worked well for me including bleeding Guzzi linked brakes which can be awkward.