Nasty front master cylinder

Thanks for all the good info & advice. I let is soak in brake fluid all night & half the day, scrubbed it out with some brushes & bore-cleaning pads (Gun cleaning kit comes in handy for LOTS of things!) and got it looking better, but by no means good. The two screws in the bottom are in there forever.

For today (Just so I might ride around the block again to "test it"), I put it back on, and pumped about 16oz of new fluid through the front system, until it started coming out nearly clear through the bleed valve. With a little help from my 11 year-old daughter working the lever, we bled it, and it is working, but not stellar. I have better brake on the rear than front. I must say, even running a little rough, this baby has a lot more pizazz than the 250's in the MSF class!! :woohoo:

I think I might try rebuilding the calipers and replacing the pads. Another Q - the manual says to take off the rear caliper, one must remove the rear wheel. Looking at it, this does not seem necessary. Am I missing something?

Thanks again gang!

got a picture of rear caliper?

Look on the underside and I'll bet it says 5/8"

I will get a pic up tomorrow (a bit dark here for one now!).

I ended up with 9 broken ribs because of a front master cylinder There are two holes under the res. One is about 1/8" which supplys fluid for the piston one is about the size of a straight pen. It reliever the pressure. If that little hole is plugged as you use the front brake it will get tighter and tighter and one more little squeze and boom you are on the ground with the front brake locked. If you are on flat ground and don't use the front brake a lot it may take awhile. You can tell because the play in the break lever will slowly get less and less. It is not getting better It would only change if you blead it again.
To get the screws out find a parts store that has jb(I think that is the name) solvent. I comes in a red and yellow spray can with black letters on it. It is good stuff. Spray it in and let is set a day. Put a good fitting screw driver in the slots and tap and turn
Be very careful the screws may mot be SS but alum. and very soft

Here is the pic of the rear master cylinder. I would think one could simply take the two bolts out that hold it together, right? The FSM says to take off the wheel, which I rally do not want to do. It states the same for the front also.

The MC does not have 5/8 on it. The rear master does, but the front does not say (at least not that I could find amongst the chipping paint!).

rgpbeme, that is scary - thanks for the info. I saw that small hole when I was cleaning up the front cylinder. It was driving me nuts that I could not get my small nail through that one, but I could through the other one. It took a a few minutes to realize it was *supposed* to be smaller!

The front brake is still a bit mushy, probably because I only have two screws holding the cover down - it just can't be air-tight.

The adventure continues!

Both the 78 750 twins and both the 79 750 twins I have had said 5/8" on the bottom of the front master cylinder, as did the ones I have bought from various people, and they are all identical to the one in your pic.

Rebuild kits are unavailable, that's why I have had so many. I should have just bought a later model master cylinder in the first place, but at least I get a little exercise throwing them out the door when they don't work

Seriously, I just did not pay attention when I had it on the bench. My attention was on the gunk inside! I am sure it is 5/8". I finally broke down and bought the one on ebay - we shall see what kind of shape it is in, though I cannot imagine it being worse. Maybe between the two I can get a good unit. The cups looked pretty good on mine, and the cylinder bore was not too bad. AND I found a new use for my gun cleaning rods & patches!

I found this a while back and just remembered it. I had it posted on the 650 site.

The '78 650 B2 model shares the brake m/c with the 78 Kaw 1000 A models, and your 78-79 KZ750 Twins..

Redline Cycle has assembled the parts and made a "kit". They do not list it as also working for the B2, but they will, trust me. I have been looking for these parts for a long time. In 1978 Kawasaki switched to a trapezoid shaped front brake master cylinder on the B2 model. Finding rebuild kits for these is impossible, because the usual companies don't make them. That means you are left to go to a dealer for the internal parts like the pistons, spring and cups. It's nice to know someone else can supply these even if the dealer can still get them. They also sell rebuilt trapezoid M/C for our bikes, again as the '78 1000 A models. Check them out, they deal primarily in the 900-1000 market.

This is a link to Redline Cycles in Illinois. The kit you need for a '78 650 B2 and a 750 Twin is the last kit at the bottom of this page.

Also, these master cyl's probably have "14" stamped on the bottom, I hink for 14mm~ 1/2"

Post edited by: OKC_Kent, at: 2006/09/20 22:36

Ok, you made me go out and check
The master cylinder I took off the 79 says 5/8", the next two I threw out the door say 14, the one currently on the 79 says 5/8", otherwise they are all identical.
Now I don't know if all four bikes had the master cylinders replaced, or if Kawasaki played "mix and match".

Oh well. with the luck I have been having with master cylinders I think it's time for me to be looking for later models with at least a 15mm bore. I need something for my four piston Tokikos anyway.

Try www.partsnmore.com

I bought rebuild kits for my 79 kz1000 mk2.