Got it. Thanks for the details. If you haven't already, I suggest the following techniques/areas to investigate:
* BLEED PROCEDURE OPTION: With a mate if need be
and starting with the left caliper first...
1) Pump front lever 10 times and HOLD it
tightly until step 5.
2) "Burp" caliper & lines by gently tapping bottom caliper with rubber mallet.
3) Tickle brake lines by hand.
4) Quickly, open and close bleeder screw while keeping lever squeezed IN.
5) Release lever.
6) Examine lines for air and repeat as needed.
* RIDER AIDS: Activate ABS during bleeding (in the event there's trapped air or dirty fluid)
* RESIDUAL AIR PROCEDURE OPTION: Overnight and AFTER bleeding the system, try the following:
1) Pump front lever 10-12 times and it hold against throttle grip with a velcro strap. Lever pull-in must be
tight against the grip on last squeeze. Ask a mate to assist so the velcro strap can be extra tight.
2) Remove front master cylinder cap and diaphragm and set aside. Gently lay a paper towel over top of reservoir (to keep foreign elements out).
3) Repeat actions of step 1 for rear brake BUT on last pump of pedal, keep the pedal weighed down with a weight on a rope or the like.
4) Repeat actions of step 2 for rear brake reservoir.
5) In the morning, DO NOT release pressure from lever and pedal. Repeat steps 4-6 of "BLEED PROCEDURE OPTION"
6) Examine lines for air and repeat as needed.
* HARDWARE: Check bleeder screws for thread integrity (I've had damaged threads allow air IN to the caliper!---fwiw, those were aftermarket bleeder screws)
* HARDWARE: Ensure all brake system rubber parts (and metal parts as required) have been replaced per periodic maintenance chart. Typically every four years. As we've discussed, OEM parts is my suggestion (unless upgrading brake lines to steel braided).
To protect against brake fluid spill damage, I FULLY cover the surrounding bike areas with old t-shirts and rags. Use tape, clips to hold them in place as needed. Much cheaper than new plastics
. Hope this info is of some use. Thanks for reading either way