Is the 15/16ths brake master cylinder supposed to be the primary ( front brakes) closer to the firewall with the larger reservoir and the smaller reservoir away from the firewall feeding the rears?

Those lines go to the NP-valve ... see your  service manual s130  available on line.. (front cil is front brake and rear is for rear cil. but go through the NP valve..)

 

Martzedcars..

Those lines go to the NP-valve ... see your  service manual s130  available on line.. (front cil is front brake and rear is for rear cil. but go through the NP valve..)

 

Martzedcars..

I'm sorry but I don't believe that is correct. Larger reservoir is always for front brakes ( Primary ) as the front caliper pistons will displace more fluid as the pads wear, as compared to the rear brake cylinders ( Drum ) or rear pistons ( Disc rear ). That is universal.

 

Also confirmed by FSM that larger reservoir is closest to the Firewall and is indeed for the Primary side. Primary piston is front brakes. Secondary piston is rear brakes.

 

OP what year of ZX cylinder do you have?   Later reservoirs are a " Divided " one piece plastic Reservoir , but larger Tank is Primary or Front brakes and is closer to Firewall.

 

Scan of 1980 FSM S130 Brake Master Cylinder:

Edited June 24, 20159 yr by Chickenman