Dual Front Rotor Set-up ?

Probably a question that has been answered before. Have recently acquired "stock" Drilled Dual Rotors off a later KZ/LTD for my 77' KZ1000A. Already have the Dual Calipers mounted. I noticed that when the dual rotors mount on the Wheel Hub, that they don't sit up as high as my original single front rotor. Of course the Single rotor set-up is a thicker rotor than the dual rotors. After I mounted everything and tested the front brake, the lever pulls in a lot more and the Piston of the Calipers move much more before engaging the rotor? Is this going to be a problem? I'm using aftermarket front brake master cylinder that might only have a 1/2" bore but worked fine when the bike was originally Single Rotor.

Dual disks need a 5/8" bore master cylinder. It needs the extra volume because you are pushing brake fluid into 2 calipers rather than 1. Ed

The smaller M/C will work but the larger is best. Try pumping the lever and do some hard breaking. The calipers might be frozen in place. They are supposed to be able to Float back and forth a small amount.
Steve

Ed, The Master that I'm just using is just an extra one I had laying around. It's one of those 1/2" bore Chinese ones. Worked fine with the Single Rotor, but now with 2 Rotors I agree I need 5/8" Bore.
I have the original one that came on the bike just has to be rebuilt. Fortunately I believe that Z1 Ent. has one rebuild kit for the front.

And Steve, I have already pulled these Calipers apart and cleaned real well. So I know at least the Left one works which was used prior with the Single Disk.

With these Dual Front Rotors being thinner ( still well within Factory Spec's ) than the Single Rotor, I was just worried that the piston in the Calipers would have to move further and that it might be a problem?

kzdcw wrote: ......................With these Dual Front Rotors being thinner ( still well within Factory Spec's ) than the Single Rotor, I was just worried that the piston in the Calipers would have to move further and that it might be a problem?

No problem. Once the brakes have been applied and released the pads only back off the rotor a tiny bit. So the pistons and pads don't move any further back away from a thin rotor than they would from a thick rotor. Ed

Ed, I thought that my Stock Front Master Cylinder off my 77' KZ1000A was 5/8" with my stock single disk rotor? Apparently it is not?

So, if that's the case I need to find me a 5/8" bore master for the front!

Single disk KZ's normally use 14mm bore master cylinders. The bottom of the original 5/8" dual disk one on my bike shown in image below so you can see how the stock ones are marked. Ed

I have a few Z1 / Z9 master cylinders at home.

Are all the 5/8 master cylinders stamped like in the photo from 650ed or is there another way to identify them as opposed to the 9/16 ones??

Are the front rotors the same diameter as your original single disc?
The 1/2" mc will work with dual discs,just feels a little different is all.

The dual rotors that I have measure the same outside diameter ( 11 5/8" ) as the stock single disc rotor I removed.

What do you think about this one to use? Says it's 5/8" bore for 7/8" handlebars? I'm sure it's a Chinese brand but New.

Same Aftermarket 5/8" front master cylinder