Master cylinder on my 81 GS750E

[nisom512]

Diagnosing my front master cylinder. I drained the fluid for just a simple replacement of the fluid because it was very old. and now I cant get the cylinder to pump at all. I opened the breather nipples and compressed it several times with nothing so I closed them and nothing so I loosened the bolt on the calipers and nothing....so I took it as far apart as I could and sprayed some break cleaner in there and it did nothing for helping me....any one else got ideas or is it just broke and I need a new one.

Thank you
Jake

 

[Guest]

Bleeding your brakes is a pain in the watchakallit . You'll have to pump up your brakes more than a few times . You need to keep everything (nipples and banjo's) done up firmly While you're pumping your lever or you'll just keep sucking in more air .
I start at the master cylinder and pump him up , hold the lever down while you crack the banjo at the master . Hold the lever down while you do up the banjo . Repeat (possibly many times) till you get fluid with no bubbles coming out .
Repeat this but crack the banjo where your front brake lines split to each calliper . Again , you'll have to do this quite a few times .
You'll still probably have no "feel" but you're getting there so don't give up .
Lastly , you go to your bleed nipples on the callipers and repeat pumping and cracking and you should be getting some good pressure . Be careful not to overtighten the nipples as they really only need to be firm . Keep going till you've got GOOD pressure and absoloodle no air bubbles. I get some small plastic hose that is a tight push on fit over the nipples and run this into a bottle with enough brake fluid in it to cover the end of the hose(s) .
Keep plenty of water on hand to wash any spilt brake fluid off EVERYTHING so it doesn't destroy your paint .

Hang in there old mate and you'll get it .

Cheers , Simon .

 

[Nessism]

You need to prime the master by sucking a vacuum on one of the caliper nipples to draw fluid out of the reservoir and into the master cylinder piston. You also need to make sure the super small fluid return hole is open.

BTW, brake cleaner is too harsh and should not be used on brake system rubber parts - bad juju there. To clean the system it's always best to dissasemble the parts and scrub them with soap and water - both the caliper(s) and master cylinder.

 

[jwhelan65]

Keep pumping it is cumbersome....