TOPIC:

I've been trying to resolve a rear brake issue for quite awhile now, including being down for nearly two years trying to source a replacement line.  Basically even without usage the rear brake would start grabbing during rides (or sometimes as quickly as a couple blocks to the store), and the more it warmed up, the worse it got.  Besides the brake line, I've also tried cleaning and swapping the caliper, or course with vigorous flushing of the fluid each time.

This weekend I dug out some extra parts from building the bike and realized I had more than I remembered.  I was specifically looking for the master cylinder but I also had yet another caliper (it was basically the whole system from reservoir to caliper).  So I pulled all that apart, cleaned up the pieces, and replaced the master cylinder and caliper together, while once again flushing out the line as each piece was added.  Took a bit of work but I figured since the master cylinder was the only piece that hadn't been replaced yet, maybe there was a chance that's where my problem was at.  Oh and I also threw on a new set of pads because of course the previous ones were almost worn down to bare metal again.

Well... so far so good!  I rode around in town a bit over the weekend, and then rode the bike to work today, and the brake was still completely releasing when I got here.  Crossing my fingers that this crap is finally fixed?

A couple of other things came up while working on this, however.  The first was that the brake pedal was always so high that I had to rest my foot on the edge of the peg to not be constantly applying pressure.  While I had everything apart I realized there is an adjustment on the master cylinder, so I screwed it all the way closed and now the pedal is finally in a comfortable position (pretty much even with the gear shifter).  Whew!

Also while it was apart, I've been wondering if maybe the pedal was bouncing while I went down the road, and why isn't there a spring to actually hold the pedal up?  I've checked the parts diagrams, there's nothing indicated for a spring other than the tiny one going to the brake light switch.  And yet while everything was apart, there is clearly a place to put a spring on these parts!  Well I can fix that -- ran up to the hardware store and grabbed a couple that looked promising, and installed the heavier one.  I think I could use something even stronger still, but it really has me wondering if THIS has been the cause of my rear brake issues?  I don't remember there ever being a spring on either of the donor bikes used to build what I'm riding, and I couldn't find anything in the boxes of extra parts so I'm not sure just how heavy this spring should be, but it's enough to keep the pedal from bouncing now.

Anyway, I thought I'd just post an update on this.  Maybe now I can find some time to rebalance the carbs as the plugs indicate two of them way out (one sooty and the other dry).

SPRING,BRAKE PEDAL RETURN PN  92081-1296

This is the part you were missing.  It's on the OEM Kawasaki parts fishe under "Rear Brake / Torque Link.

And there is a tiny little port in the bore of the master that allows fluid to return after pressing the brake.  Yours must have been plugged up.  It's a very common problem, because the port is tiny, and easily plugged.
 

Thanks for the update. Yes, here is supposed to be a return spring.Part number 92081-1296.

www.partzilla.com/catalog/kawasaki/motor...ke-pedal-torque-link
 

Clearly Nessism types faster than I do. Yes, in the master cylinder there is the obvious fluid return hole as well as a much less obvious, tiny bleed hole that can easily get plugged..
 

The spring usually wraps around the brake lever pivot. Ed's right about that little hole. A little crud and it won't vent. 
Steve

This one is different. 
 

@Nessism -- I saw that spring on the parts diagram, but the way they positioned it in the picture makes it look like they are showing the spring which goes to the brake light switch.  My switch spring is very lightweight but has the U-shaped ends like shown, so I ignored that one.  However the other end of the V-shaped brake lever has a slot in it, and the place where I though the other end of the spring attached to is this shaft on the back side of the pedal plate which doesn't go to anything else but has a grove near the end in like with the V lever.  I simply got a spring with a full loop on each end.

As for that little tiny hole on the master cylinder...  ok I must have been confused because I thought everyone had been telling me there were return holes in the *caliper* and that's what I've been trying to clean/replace.  Eesh.

@SWest -- wow that thing is way more massive than the spring I picked up.  OK gives me a better idea of what I'm supposed to be looking around for at least.  Does it actually attach to that shaft on the back side of the pedal plate, or is there another spot I'm supposed to hook it to?

@TexasKZ -- I might try pulling apart the master cylinder I just removed.  I think the replacement has a leak, I'm getting brake fluid dripping on the exhaust, but the thing has been sitting for many years so I wasn't sure if it might seal itself up again with some usage.  Now that I'm looking at this instead of the caliper, the return hole might be more obvious!

This is the least bad picture I could find. Obviously, it is for front brakes or a hydraulic clutch. Never the less, you can see in the bottom an obvious fluid port. Just above that, under that area of bubbles, you can see what looks like a depression where somebody started to drill, and then changed their mind. In reality, at the bottom of that depression is a tiny little hole that is necessary to relieve pressure in the system. If it is clogged, pressure will keep building up until the pads are firmly against the disc and the pedal or handle can no longer be depressed. 
The hole is easy to overlook and it is easily clogged.

 

Well the trip home was also uneventful, in that the brakes worked perfectly and were still releasing completely when I arrived home.  It's going to be 95 here on Wednesday when I ride in again, that should certainly give them a workout (plus a section of my trip is torn up to a single lane of construction traffic so they a bit of a workout there).  Who knows, maybe this set of brake pads will actually last more than a season?

Hopefully the spring is all it needed.