Help With RX on Bleeding Front Brakes

[Red_Hen]

Hi Gang,

I realize this space is reserved primarily for R65's but since it's a brake issue and the same type of system on the R65's with the dual Brembos, I hope it's okay to post my request of help here!

This has to do with the front brakes on my K75s

When I returned from the Sedalia, MO rally, I decided to overhaul the calipers up front and try EBC HH pads as I've got some brake shutter & pulsing again. I'd installed the EBC floating rotors @ 15k miles ago but then used a new set of CL A3 pads I happened to have on hand. The new rotors helped a lot.

Prior to removing the calipers, I drained the brake lines. The fluid was very dark - definitely time for a change. When I popped out the pistons, there was some contamination inside. So it was a good move to get in and clean things up.

I have Spiegler S/S lines front & rear and believe the front master cylinder to be in good shape.

Spent the better part of this evening w/out success! Read on a previous thread about pushing the caliper pucks in - what's throwing me off is when I re-assembled them I did push them down all the way. I put all the seals where they're supposed to go. I installed the new pads & mounted the calipers over the rotors.

The Clymer manual mentions bleeding the master cylinder - not sure if they mean to put my thumb over the big hole inside the plastic reservoir or over the hole where the banjo bolt goes in - tried it both ways and I basically wound up with dribbles of brake fluid over a piece of plastic I'm using to protect the bike from brake fluid - nasty stuff!

I used my US General Brake Bleeder to pull the brake fluid through the lines without success. Also used an oil can to push the fluid the other way. I've read a windshield washer pump connected to a 12v battery makes a good vacuum for pulling the fluid through the lines.

If pushing in the pucks means removing the calipers and new brake pads, I'll take them off. This task is more complicated than I figured!

Appreciate any suggestions!

[montmil]

Ken, When you crack the bleeder screw, are you seeing brake fluid expelled as you pump the lever?

[Julio A.]

Does the K75's master cylinder similar to the ones on the R65?

I also encountered this problem before. I overhauled the entire brake system and when it was time to put in fresh fluid, the fluid won't go down to the calipers. Fluid pressure was building up when tested directly on the hole where the banjo enters but amazingly, fluid still won't reach the other parts of the system.

The problem eventually was traced to a really small hole that was clogged inside the master cylinder reservoir. As soon as I pricked it open using a needle, bubbles immediately started to come up.

Note that this hole was still clogged after a thorough wash and brush. It really took something solid like a needle to displace the blockage.

[tvrla]

I'm assuming the master was working before the overhaul, so it's something to do with technique.

When bleeding the master, block the outlet where the brake line attaches. Fluid will want to push your finger out of the way and spray everywhere once pressure builds up, so be prepared.

Air gets trapped at the high points, so either lifting the caliper, jiggling the lines or filling from the bottom of the system helps that.

Sometimes, it's just easiest to strap the brake lever to the bar and leave it over night. It leaves the bleed hole open and the air eventually rises to the high point (the master cylinder) and escapes.

[Red_Hen]

Let me answer as follows:

Monte: Ken, When you crack the bleeder screw, are you seeing brake fluid expelled as you pump the lever?
On the right side I think so but not on the left.

Julio: relief hole on m/c is working as it should.  When I squeeze the brake handle is bubbling.

Wirespokes: I believe it's a technique issue.  I really don't understand the concept of bleeding the m/c and removing the banjo bolt causes the fluid to go everywhere and putting it back on isn't as quick as the Clymer book suggests - lining up the banjo bolt is tricky.  Maybe leaving the brake lever engaged overnight will get me moving in the right direction.  If I try that route of strapping a block and holding the lever overnight, should I crack the bleeder screws?

So far stumped.

[montmil]

Ken, Are you bleeding the brakes individually? Begin with the caliper farthest away from the master cylinder.

[tvrla]

Monte - I don't think there's one farther from the MC than the other - there's a splitter and both lines take off from there. I think they're equal length.

As for bleeding the MC - you won't get all the air out of it, and you won't be able to get it so it doesn't leak putting the line back on. However, once the MC is pretty well purged, replace the brake line, and then bleed the connection like you would a bleeder - squeeze the lever, crack the connection, close, let the lever back.

Pull the brake lever gently. Build up pressure, and that sqeezes the air out. Don't pull much more than about half stroke - about the distance travelled in normal operation.

When strapping the lever to the bar, nothing else needs to be done - and definitely don't crack the bleeders!

[Red_Hen]

Thanks, Terry & Monte

The moderator of the K Forum at MOA suggests:  I'll give this a go and report my findings - shouldn't be such a big deal - I know I'll get this tackled - thank!


Remove calipers from forks. Put wood blocks between pads to keep pistons all the way retracted.

Turn handlebars ALL the way to the left. Leaving the bars straight ahead allows air to get trapped in the master cylinder and making it almost impossible to even start getting the master bled.

Bleed brakes.

If you are going to manually bleed it using the brake lever, put a 1/2" block between the lever and the grip so that you do not push the piston in the master cylinder into an area of the cylinder where it normally doesn't go. Any pitting in that area can cut the lip of the cylinder seal.

You can use suction at the caliper bleed screws or manually push it through the master using the lever and opening and closing the bleed screws.

[Red_Hen]

I'm not the guy you want to ask for help on brakes - good thing I'm not a perfesional mechanic - I'd be in jail!

Brakes now bled & all is well now that I realized if mixed the outer covers on the calipers - my friend came over yesterday to help me set the timing on my Honda SL125 that's going bye-bye.

I casually mentioned not getting brakes to bleed - he casually commented how on the cars he works on the bleed screw points up - that comment activated my subconscious - 3-4 hours laterwent back to garage - kept looking at calipers - "something's wrong, something's wrong"

Finally realized what I'd done - always a good idea to put lefts & rights in different parts bins or tag - knew there was a solution here!  [smiley=bmw_smiley.gif] [smiley=birthdays.gif]

[montmil]

Yep. It happens with car guys, too, when they mix up brake calipers while doing an upgrade. I've seen two in my experience.

[Matt Chapter]

Yep. It happens with car guys, too, when they mix up brake calipers while doing an upgrade. I've seen two in my experience.

Cue the classic joke about red and green calipers on expensive Italian machines....

No, I can't remember what it is or the punch line!