Rear brake dragging.

Hello again,

Recently ran into a brake dragging issue, eventually got to the point of not being able to push the bike (without throttle). ordered all new rubber and rebuilt the caliper, cleaned the line, cleaned the master cylinder, and the reservoir. Bleed the system and it worked great until about 15 minutes into a ride, it started to drag again but not nearly as bad as it was.

The piston itself looked fine for the most part, but some browning here are there (I should've checked for pitting better my b!)

anyways i'm wondering if a bad piston could cause dragging? or do I need to replace something else. just would like opinions before I buy one of those expensive pistons...

The master cylinder has a hole in the bottom that prevents this from happening. Sometimes the tiny hole will get gummed up and prevents the piston from releasing. There are two holes in the master the one you want is the small one.

The manual says not to remove the primary cup, secondary cup, or spring from the piston or it will be damaged.

can i access these holes without damaging these? does whole piston (including the attached cups and spring) just slide out?
also where would the holes be?

Thanks, sorry for abundant of questions. just trying to be prepared before I take it all apart again, want to get it right this time.


If not, z1 ent. has this piston assembly, says "FRONT" on it but it clearly is a rear piston correct? looks a little longer than the piston in the manual diagram...

www.z1enterprises.com/piston-comp-brake44fr.html

The only way to get the master cylinder really clean is to completely disassemble it. The piston and its cups will come out together. Clean it with fresh brake fluid. If the rubber bits are in any way suspicious, replace them. If their age is unknown, replace them. If you know they are more than five years old, I would replace them. There is a circlip holding the piston in the master cylinder, and it can sometimes be a pain to get out. A good circlip plier and a bunch of patience will usually get it out. You can see it in the parts diagram here-
www.partzilla.com/catalog/kawasaki/motor...rear-master-cylinder


In the bottom of the place where the pipe from the fluid reservoir enters the master cylinder, are two holes. One will be obvious, the other is really tiny and easy to overlook. If the tiny one is clogged. Fluid will build up between the primary and secondary cups, finally forcing its way past the primary, causing pressure to build up in the line little by little until the brake will not release. A really fine steel e string from a guitar should be small enough to clear any really hard debris, if compressed air will not.

Also, if the flexible brake hose is really old, replace it. Barnacles will form inside the hose, and in rare cases, the hose can come apart inside, both of which can impede the fluid.

There can also be problems with the caliper, but it seems that the master cylinder is most often the culprit.

One more thing. Does the brake pedal move freely? The pivot can get rusty and gummed up so badly, that the spring cannot bring the pedal back up, thus causing the system to stay pressurized, not releasing the brake.

Ok, one more one more thing, Look for a post by user loudvhx. In his signature line are links to his web pages that contain a bucket load of information about various 550 models.

Very insightful thank you.

wanted to do a canyon run this weekend... absolutely HATE waiting for parts. so I'll see if I can take it apart and reuse the piston for now... when I took apart the caliper there was gummed up brake fluid behind it. so very high chance the master cylinder is plugged up too. Didn't get truly inside it the first time due to not owning circlip pliers, looks like I need to get a pair today.
Yes the brake pedal has good action (switching to rear sets soon, that'll give me a chance to lube too.)

Thanks for the help, I'll be back with results

You may be able to remove the clip with a small screwdriver, or even a pick.

pick? i could barely get the clips out with the proper tool lol.

Took apart the master cylinder and cleaned both holes, used a brass bristle for the small hole and compressed air.

cleaned everything else, put everything back together and bled it and it started to drag again after some use.

It will start to drag as i use it, but never get to a crazy amount of drag. Last time i parked it for the night and came back the next morning and the drag was gone.

any advise?

If the pedal snaps right back to its stop when released, and the piston in the master cylinder moves easily and the holes in the cylinder are clear, and the brake hose is in good shape, then all that is left is the caliper.
Might be spooge in the flier passage, improperly installed seals, or incorrect seals that restrict piston retraction.
May be zombies.

I guess I'll give a shot at replacing the piston itself. I put a new seal in there, hopefully it isn't wrong...

so disappointing, really felt like the master cyl passage was the answer

Check the groove where the piston seal fits and ensure it's absolutely clean of any buildup.

If the piston is clean, I doubt it is the problem. If it has some deep pitting, it might leak a little. Do double check the seal grooves to be certain they are spotless. If there is crud under one of the seals, it could cause too much pressure against the poston.