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Master cylinder

I did exactly as Bodeen explained and it worked like a charm. First time since I owned the bike the front brakes actually work as they should. Thank You for the help.




Bodeen said:
I've had this problem in the past and tried most of the tricks at one time or another. They didnt work on mine. What did work, was to remove the calipers one at a time, remove the pads, use a small block of wood or paint stir stick to clamp one side of the caliper pistons in place with a C-clamp. Then carefully pump brakes until the un-clamped pistons protrude until you see clean piston. NOT too far the piston will come out of the bore and make a brake fluid mess. Now remove the lid on the masrter cylinder and slowly by hand push each piston back in. continue to do this for each pair of pistons. Keep in mind that you have to put the master cylinder cover back on to pump out the next pair of pistons. I guarantee that at some point in the process you will get a BIG bubble of air to escape through the master cylinder. I would also bet that it will come from one of the top pistons where air gets trapped and cant escape without force.
While your in there you may as well get an old toothbrush and brush the sides of the pistons clean with some clean brake fluid. Clean the pins and use some brake grease on them during re-assembly.
Let us know how you make out.
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Bodeen said:
Keep in mind that you have to put the master cylinder cover back on to pump out the next pair of pistons.
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What a Great thread. I learned a lot about brakes.

Bodeen, why do you have to replace the master cylinder cover before you move onto the next piston? Is it because of having too much fluid in the MC reservoir?
 
Hoople said:
What a Great thread. I learned a lot about brakes.

Bodeen, why do you have to replace the master cylinder cover before you move onto the next piston? Is it because of having too much fluid in the MC reservoir?
Click to expand...

I do it when pumping out the next piston or two just to keep fluid from flying. I've tried it with it off but I always seem to make a mess. The bubble that is inevitably released by doing it this way seems to burp out a bit of a mess too.
I do this to my brakes about twice a year, clean everything up good and I never have a bad brake pull.
 
jachey said:
I did exactly as Bodeen explained and it worked like a charm. First time since I owned the bike the front brakes actually work as they should. Thank You for the help.
Click to expand...

I'm happy it worked out for you. This was the only way I could get my brake pull back to normal.
 
ONCE YOU AT THE BLEED-THE-BRAKE STAGE( AFTER CLEANING COMPONUTS UP. I TAKE THE brake lines off & let them drain overnight.( use new copper crush washers) then i use a oil pumper can , hooked up to thin plastic line(you can hook both ft. calipers up at once by makeing a "T" line with a vacuum hose T.
hook the hose up to a new can of brake fluid.i like ATE genuine "super blue or
amber" tented fluid. syn. 15.00 per ltr. google it.
pump the fluid into both brake calipers at the same time. you can see when all the air is out of the calipers then fill the resivor 1/2 full.
then give the brake lever a squese & close the bleeders.
also you might use SPEEDBLEEDER.COM BLEED SCREW. IT HAS A CHECK VALVE IN in to prevent air from getting into the system when you let-go of the brake lever.hope this helps
 
Hoople said:
What a Great thread. I learned a lot about brakes.

Bodeen, why do you have to replace the master cylinder cover before you move onto the next piston? Is it because of having too much fluid in the MC reservoir?
Click to expand...

1 you dont want to pump fluid all over the bike and 2 you will have the proper level of fluid to start with as the gasket on the cover pushes down into the master
 
This is such common problem. I have it on my bike (2000 Road King Classic).

While doing other work I replaced all the brake lines with new steel braided ones, all the crush washers and rebuilt the master cylinder and put on speed bleeders. All of this made a marginal difference but eventually it comes back. think I will try Bodeen's method next. Either that or I may invest in a phoenix bleeder system with a motorcycle adapter to force fluid in from the bottom up. It's pricey but if I have to keep doing it then it may be worth it and I figure I can use it on the cars too.

I have front end work I may do this year and if I do I may just replace the calipers with six piston ones, don't know if that would make it worse though. I would love to have this problem "go away" permanently.
 
IT'S FIXED!!!!

I did a similar technique to Bodeen's. What I found was that two pistons (one on each side) were not coming out as far as they should. I forced them out as far as I could without popping them out by having my wife gently pump the brake while I used a screwdriver on the backside of the pad to hold the other pistons in. Then I cleaned everything. I mainly used alcohol but I also used some Brake clean sparingly. I say sparingly because the can says it can eat rubber and paint so I was very careful with it. I cleaned every piston, all eight.

Then just for completeness and because I had someone there, I vacuum bled the brakes with the vacuum bleeder I've had for years. My wife made sure the m/c did not get too low while I watched the short tubing line (must make longer one) and worked the bleeder screw. There really wasn't any air but I was making sure.

Result: Better than I ever remember these brakes being. Two finger pull to stop, no pumping, rock hard, lots of feedback. In short just what I wanted.

Turns out the pads were not seating properly on the rotor so everything felt low. Pumping extended the stuck pistons a bit and the other ones more but they would go back. You can see this when you have the caliper off and watch it. I cannot get over how much better they are.

Hope this helps someone.:bigsmiley12:
 
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