Need help--Brake pedal goes all the way to floor after several new parts replaced Options

[914xr75]

I posted a few weeks ago about leaking reservoir tubes under the gas tank. I replaced those and the leaking stopped. I bled the calipers, but did not bleed the master cylinder. This was the first time I had about 5% stopping power and the pedal went to the floor, not sure if you'd call it spongy, but there was no resistance. That was a couple weeks ago.

Today I replaced the master with a 17mm ATE, rebuilt one of the front calipers, replaced the front soft lines. The rear steel lines still looked good, so I left them. I bled the new master. It took about an hour of pushing out air bubbles, and two quarts of brake fluid into the system to complete the MC bleeding. Once done, the pedal was still pillow soft.

Now on to the caliper bleeding--I purchased the Motive pressure bleeding system. Pumped it up to 5 psi as recommended by Ian Karr. About 30 seconds later the Motive bottle was at 0 psi. There aren't any fluid leaks in the brake system. I replaced the reservoir seal and added Teflon tape to the fitting in the Motive hose. Still loses pressure.

I tried the HF bleeder you hook up to your compressor. For 3 minutes about 5% fluid and 95% air entered the bottle. About 8 ounces of fluid came out. That is where I left off after a full day of brake work. Then I thought, did I cross the reservoir lines? I don't believe I did that, and I don't think that would cause my situation.

Any help you can offer would be greatly appreciated. Sean

[914xr75]

Tonight's update. Pulled the tank again to look underneath for leakage. No leaks, but I jiggled the reservoir tubes and bubbles came up from the master. Finally located the pressure regulator, thanks
fiacra. Gave it some rubber mallet love.

Pedal cluster floor was dry. Took my time using the long tube method. Began the bleeding process once again. At the end I finally had a hard pedal. Hooked up the Motive to see if the system holds the pressure steady.

Pumped it up to 15 psi and lost about 2 psi every 30 seconds. This is light years better than yesterday. I could not locate an air vent or a overflow on the reservoir. Tomorrow I will inspect it with a microscope to find the vent and overflow. That is probably the last issue. I did put my ear up to the reservoir while the system had the 15 psi in it. I did not hear air escaping.

Had I not hooked it up to the Motive bottle, I would have thought the job was done.