Aftermarket front master cylinder

I had an issue before, when I originally went to replace the front master cylinder on my KZ1100 A2, with the new master cylinder not having a large enough piston bore for the dual-caliper setup. I believe I got a 14mm bore and it was recommended I get a 15mm. I ended up simply rebuilding the original front master and sticking with it. Next go-around I purchased a 17mm bore piston master cylinder and am still having issues with not enough pressure. (similar to these: alexnld.com/product/7-8-motorcycle-cnc-h...linder-clutch-lever/ ) I even replaced the brake lines with good speigler lines. Any recommendations on reasonably priced masters($150 range for both left and right) that have the appearance of those, but actually function? Also, need left AND right hydraulics, no clutch cable.

The stock dual brake master cylinder that came on my KZ650-C1 is 5/8" and is marked as such on the bottom (see image below). 5/8" = 15.875mm. Ed

Did you rebuild your brake calipers? Replace the seals with OEM Kawasaki parts? If not, you may want to consider it. When the caliper pistons are binding in the calipers the pistons don't move close enough to the disc and the result is a very spongy feel at the lever. Tieing the lever back to the bar sometimes helps facilitate the piston moving closer to the disc but if the caliper is dirty and/or if someone installed some crappy aftermarket caliper piston seals that little work around may not work.

Yes the calipers were rebuilt. With the stock master the brakes are nice and tight not a bunch of play. Is it possible those aftermarket ones, while they have a larger diameter don't have a long enough throw? Or do I really just suck at bleeding brakes Haha! I have a vacuum pump to bleed with, pulled a whole 12oz jug of fluid through, no bubbles anymore.

On my project bike i use a 1/2" ( single disc ) MC on dual Tokico 6 piston calipers..
Others say you need a 5/8" MC but i am not able to pull the brake leveler with both hands more than half the way.
A good bleeding, new seals and clean and easy sliding caliper pistons are recommended actions.

rokit_armor wrote: Yes the calipers were rebuilt.

Where did you get the seals? Did you use OEM or K&L?

I honestly dont remember, probably got them from Z1. Why could it be the caliper seals if the brakes work fine with stock master cylinder but not the aftermarket?

No eBay APP ID and/or Cert ID defined in Kunena configurationI have been tossing around the idea of replacing the stock "box" master cylinder assembly something more modern with a remote reservoir. I have seen the one you have in the link above, and the that low of a price, it makes me wonder/worry about the quality, and replacement parts if ever needed. I'll be searching for one off another newer bike, then adapting it to my current dual single-caliper system. Just a thought here.

Something like this, and it is also 5/8.

rokit_armor wrote: I honestly dont remember, probably got them from Z1. Why could it be the caliper seals if the brakes work fine with stock master cylinder but not the aftermarket?

If the brake lever was firm before but it isn't since changing the master then the master would be the first thing I'd look at. From what you say though I'm not sure what to suggest unless your new master is bad.

Regarding the piston seals, I've had lots of problems with K&L brake caliper piston seals as sold by Z1. The pistons were binding and this caused a spongy feel at the lever. From what you say this seems like an unlikely cause for the problem on your bike though.

One other thing I've seen is crud inside the original brake lines contaminating the system. That's why I always replace the original lines with stainless. Check insurance. I just don't like taking chances with brakes.

If this helps, I'm in the process of resurrecting my 89 ZX-7, and it's front master cylinder have 5/8. Currently rebuilding the master with rebuilt kit and 5/8 ball-hone.