Z650 dual disc size

Hello everyone and anyone,

Just wondering if someone can help me. I have a basket case of a Z650 1977 , I purchased this some years ago and have started to fix her up.
I have what I believe to be a 1979 with dual disc B3.
The disc diameters are 277mm x 5mm thick (badly scored) with 9 x rivets and 4 bolt pattern.
I loosely fitted the wheel to the forks the other day and the discs sit very close to the mounting bolts of the callipers.
I need to replace the discs with new ones or decent second hand ones.
Why worry is that because I purchased (stupidly) in bits I don't if I have the correct forks or callipers or discs for that matter.
Can anyone tell me what size disc an Australian Z650 1979 dual disc diameter should be and if the callipers are forward mounting or reward of the forks.
Cheers

The KZ650-B3 did not come with dual disks, so if yours has them someone fiddled with things. Please post pictures as that will help.

Is your 1977 a B or C model KZ650? The 1977 KZ650-B1 had a single front disk brake mounted in front of the forks and it had wire wheels. The 1977 KZ650-C1 had dual front disk brakes mounted rearward of the forks and it had cast wheels. The disk rotor on the B models was not the same as the disk rotors that came on the C models. The KZ650-B front rotor was 6.9 - 7.1mm thick with a 6mm service limit. The KZ650-C front rotor was 4.9 - 5.1mm thick with a 4.5mm service limit. The B and C disk rotors also have different effective disk diameters. Ed