Ok if the front brakes are being operated out of the front reservoir, then almost everything I have said may be wrong.
Here's the deal
Inside your M/C are two pistons linked but operating independently.If you were to disconnect the line to the rear brakes, and then stomp the brakes, this is what goes on; The footpedal is connected to the pushrod, which is connected to the rearmost piston. the end. Pedal goes down, piston moves forward. On the front of the piston is a Mini pushrod. When the rear piston moves forward the mini pushrod eventually reaches the front piston. If you have enough pedal travel left, the front piston will push fluid out to the front calipers. if you still have pedal travel left the brakes will apply and the pressure will build, stopping the car.
So the two most important things are sufficient pedal travel, and the front piston returning to its rear-most parking spot. Since SSBC in there infinite wisdom swapped the working chambers, rear to front, there is now no mechanical way of pulling the front piston to it's rearmost parking spot.So how are they returning the piston? ima gonna assume there's a spring in there, cuz seal retraction is not going to do it.Moot point cuz we already know it's returning by the fact that it is bleedable. Whether or not there is enough volume ahead of the piston to affect good braking I cannot say, except that, probably not, cuz if there was then you would not be having this problem.
Another possibility is that a pocket of air exists in the front system.Air is compressible,so some of the displaced fluid is used to compress the pocket and not leaving enough fluid to properly apply the calipers. You are gonna have to hunt for this pocket and get the front system working 100% first.If you spend a buncha time on the rear system, but can never get the fronts, well, that would be a total waste of time.Perhaps this is why the guys are talking about the bigbore M/Cs. The 1 1/32 chamber, at the same stroke, will displace 12% more fluid. To my way of thinking this is a design flaw. I hope you have teflon hoses up front.They have a much stiffer flex-resistant design. This will ensure a better caliper application.
So that's the front mechanical half.
Now lets say the rear system was working perfectly. In this case the only difference to the front system is that the mini pushrod is replaced with brake fluid, and the front piston is hydraulically locked to the rear piston. If the rear system fails, the rear system pushes the hydraulic fluid out and the mini pushrod is again called on to stop the car as in the previous description.
Once the fronts are working with the mini pushrod, you will have to bleed the M/C , so that the rear chamber is air free, before you can proceed to the rest of the rear.
Now getting back to the fronts;
I would really like to know how much reserve stroke that system has. And you should want to know as well.Here is how to figure that out; Have a helper jam on the pedal really hard, two feet hard. Then crack a bleeder.The pedal will, of course, drop.The amount of drop is the reserve. I would also capture the fluid expelled from the bleeder and measure it.
This volume represents the reserve. If you get just 1 or 2 cc,and, if you are absolutely sure there is no air in the system,then the system is less than marginal, allowing almost no room for error; as in hose flex,pad flatness, or caliper flex..I would either move back to the 1 1/32 M/C and live with the pedal feel or abandon the system entirely.
But if you get something like 4 or 5cc then that is pretty good. Between 2 and 3 is probably marginal, get the teflon hoses.
