NIMMO
Race Dog
Hi guys had to replace my master cylinder on my front brake R1100 GS, here is the step by step should anyone need it.
Found a lot of info on this topic on net but in my opinion some unnecessary steps.
Get all your other vehicles away from your working area, brake fluid doesn’t ask questions and rather safe than sorry. Put bike on main stand and secure front wheel so that it can’t turn and spill fluid onto bike.
Cover bike with some wet cloths and make sure all your painted surfaces are protected.
Remove the hand guards and mirror.
Unscrew the switch unit and the micro switch for the brake light; you don’t want to spill fluid on them.
Remove the lid from the reservoir and using a syringe remove as much fluid as you can, the grit left behind you can remove using an ear bud.
Some manuals say you must remove the throttle cable and banjo bolt that fixes the brake line to the reservoir. I chose not to do it simply because I could not see the use of it. Should you remove the banjo bolt you would then also need to replace the washers and there would be more air in your system. Also the throttle cable was not blocking anything.
After cleaning the reservoir stick some cleaning / toilet paper in the reservoir, I accidentally pressed up against my brake lever and squirted myself and some of the cover protecting the bike….
For every bolt you loosen from now on keep some paper underneath it to prevent spillage.
Loosen the pivot bolt under the lever (where micro switch was) and pull down on the bolt to get it out. The lever will come out exposing the piston.
Press the piston back and clean all the grit in the sleeve that would prevent it from coming out. Press and hold the piston back while you loosen the retaining bolt that is on the bike side just underneath the reservoir. When the bolt is out the piston should come out, if not it’s the grime holding it back. Clean the area again until you can get it out. Remember there is a spring forcing it forward so be careful not to have it jump out.
If there is some scuffs inside the bore gently sand it with some water paper (500 or higher) using some clean DOT 4 as lubricant NOT water. Clean the whole area surrounding the sleeve. Once you are satisfied with the prep work clean the bore using some paper with some new DOT 4 as lube.
The piston kit consists of a piston, spring, and new retaining bolt with collapsible washer. Assemble it with the lube on the outside for the brake lever ball joint.
Use some DOT 4 to lube the seals on the new piston before inserting it in the bore. Press the piston back and turn the new retaining bolt in. Clean the rubber booth and brake lever and first slot the booth in position before replacing the pivot bolt (give it some tread lock).
Take the paper out of the reservoir and fill half way, gently pull brake until no more air comes out of the return hole in reservoir. When the air is out and lever feels firm, pull and hold while loosening drain bolt on brakes at callipers. Keep on pulling lever towards handle to bleed brake fluid, before releasing lever tighten bolt again. (You will notice air bubbles in the fluid pressed out, continue till you don't see any more bubbles) Repeat on both sides. Fill reservoir to level and replace cap.
Replace switches and covers and you are done.
Found a lot of info on this topic on net but in my opinion some unnecessary steps.
Get all your other vehicles away from your working area, brake fluid doesn’t ask questions and rather safe than sorry. Put bike on main stand and secure front wheel so that it can’t turn and spill fluid onto bike.
Cover bike with some wet cloths and make sure all your painted surfaces are protected.
Remove the hand guards and mirror.
Unscrew the switch unit and the micro switch for the brake light; you don’t want to spill fluid on them.
Remove the lid from the reservoir and using a syringe remove as much fluid as you can, the grit left behind you can remove using an ear bud.
Some manuals say you must remove the throttle cable and banjo bolt that fixes the brake line to the reservoir. I chose not to do it simply because I could not see the use of it. Should you remove the banjo bolt you would then also need to replace the washers and there would be more air in your system. Also the throttle cable was not blocking anything.
After cleaning the reservoir stick some cleaning / toilet paper in the reservoir, I accidentally pressed up against my brake lever and squirted myself and some of the cover protecting the bike….
For every bolt you loosen from now on keep some paper underneath it to prevent spillage.
Loosen the pivot bolt under the lever (where micro switch was) and pull down on the bolt to get it out. The lever will come out exposing the piston.
Press the piston back and clean all the grit in the sleeve that would prevent it from coming out. Press and hold the piston back while you loosen the retaining bolt that is on the bike side just underneath the reservoir. When the bolt is out the piston should come out, if not it’s the grime holding it back. Clean the area again until you can get it out. Remember there is a spring forcing it forward so be careful not to have it jump out.
If there is some scuffs inside the bore gently sand it with some water paper (500 or higher) using some clean DOT 4 as lubricant NOT water. Clean the whole area surrounding the sleeve. Once you are satisfied with the prep work clean the bore using some paper with some new DOT 4 as lube.
The piston kit consists of a piston, spring, and new retaining bolt with collapsible washer. Assemble it with the lube on the outside for the brake lever ball joint.
Use some DOT 4 to lube the seals on the new piston before inserting it in the bore. Press the piston back and turn the new retaining bolt in. Clean the rubber booth and brake lever and first slot the booth in position before replacing the pivot bolt (give it some tread lock).
Take the paper out of the reservoir and fill half way, gently pull brake until no more air comes out of the return hole in reservoir. When the air is out and lever feels firm, pull and hold while loosening drain bolt on brakes at callipers. Keep on pulling lever towards handle to bleed brake fluid, before releasing lever tighten bolt again. (You will notice air bubbles in the fluid pressed out, continue till you don't see any more bubbles) Repeat on both sides. Fill reservoir to level and replace cap.
Replace switches and covers and you are done.
