Master Cylinder rebuild 1/2\"to 5/8\"

I am rebuilding my front end forks, brake, and master cylinder, problem there is no rebuild for my 1/2" master cylinder I looked on Z1 enterprises, e-bay old bike barn googled everyting under the sun. I came up with a 1980 kz750 dual brake system off e-bay same master cylinder and calipers "single" piston same size banjo screws, and master cylinder only in 5/8" there are many rebuild kits, I have been looking for over a month for a 1/2' rebuild kit I am going to use the 5/8" master cylinder on my kz 750 twin. I think my brakes should perform the same or better than the 1/2" master cylinder. If anyone has experience with this conversion, or knows if I am going to fail let me know I am going forward this week. Itching to ride this bike now been 3 months down tinkering with rebuilding, know it will be worth it this summer though. Wife is rideing my @$#%^ to get it running

78-79 KZ750 twins had a 5/8" master cylinder with single disk brake stock. The 82 (like my 80) had the brake light switch mounted on the master cylinder while the 78-79 had it mounted on the brake line junction block below the headlight. If the master cylinder you are using has the brake light switch mounted on it, then it should be a direct bolt on, if it don't, then you will need to use a junction block to mount one on the lower triple clamp below the headlight.
I assume you are not converting to dual disks, since the right fork leg has no provision for mounting the second caliper.

Post edited by: steell, at: 2006/03/26 08:52

The brake light switch is mounted on the master cylinder for both the 1/2" and 5/8". I will still be using the single disk brake, will the 5/8" master cylinder perform on the single disk set-up as the orignal 1/2" master cylinder. I have the entire dual brake system off the 1980 kz750, which is a dual disk brake set-up only using the 5/8" master cylinder will that perform the same or better than the original 1/2" master cylinder. Read on the archive that the 5/8" has longer brake lever pull, but more bite. Archive does not specifically refer to the 1/2" to 5/8" conversion I am researching.

If the twin uses a 5/8 master with a single caliper, is the caliper piston larger than that of a dual caliper?

Or is it just that the twin is lighter than a 4-cyl, so needs less braking power?

The 78-79 750 twins with the 5/8" master cylinder use the same calipers as the 78 (and probably others) KZ1000. I don't have a clue why Kawasaki put the 5/8" master cylinder on the 78-79 twins, but that's the only years that had them.

5/8" master cylinder requires less lever travel but more hand pressure than the 1/2". Not really a noticable difference though, I converted a 79 750 twin to dual disk (already had 5/8") and a 80 750 twin to dual disk (was a 1/2" but I installed a 5/8") and the only difference I noticed was an increase in stopping power.