Brad -
First of all... Welcome Aboard !

Air inside your hydraulic brake lines is the issue.

First of all, Jap bikes follow a very precise brake hose layout that naturally results in that "hard" brake lever. This design never includes loops in the brake line or hose layouts where the master cylinder is not the highest portion of the hydraulic system. The result of this is that air naturally travels upward through the plumbing and naturally accumulates at the master cylinder, where it is allowed to "self bleed" its way into the m/c reservoir. Therefore, no matter how mentally challenged the owner might be, all he has to do is pour brake fluid into the reservoir and then start pumping the lever. Air wants to leave these systems by design.

However, the Germans have slightly different ideas. (Maybe you've noticed ?!)

1978 model probably has the ATE front caliper with the under-the-fuel tank master cylinder.
• First of all, the loop of flex hose coming off the fork leg may go slightly downhill as it makes its way to the frame attach point. You can't have that or air will accumulate there inside the line. Most of the time, merely pushing the hose to one side, or keeping it gently lifted, creates a gentle uphill flow over the full course.
• Secondly, the under-tank m/c is tilted slightly up hill. In it's factory position it can never fully bleed itself. So you'll either need to unfasten it from the frame or roll the rear tire up onto something about 4-6" higher.
• Thirdly, the German m/c can only self-bleed when the piston is allowed to fully return to the circlip stop. So if there is old brake fluid crud stopping that physical position from being obtained, then air can't come out of the system. This situation can also happen if you have your brake cable adjusted too tightly. The m/c piston MUST be 100% fully extended at rest.

If you'll do these 3 simple steps, the system will start to self bleed during 100 SLOW and STEADY pulls on the brake lever. With the cap REMOVED, watch the pool of brake fluid within the reservoir. You should see a progression of "Champaign bubbles" coming up in the reservoir. That is your problem air leaving the system and then being replaced with fluid. The more viscous the fluid the longer this process takes.

When the lever starts to get hard, you can also do a traditional bleed at the caliper to remove entrapped air within the caliper. Take your time. Operate the lever slowly, and it will get better.

► However, your brake lever will NEVER be as hard as your Jap bike lever for 2 reasons... You've got the extra built-in stretch of the front brake cable. You've got the expansion of the OEM rubber hose. I highly suggest you change over to "stainless steel brake hoses" as per THIS THREAD.

Hope this helps.

Still futzing with this brake issue. I did all of Wobbly's suggestions. Someone else mentioned having the bleed nipple point vertical. That released more trapped air. I put on a steel brake line. (which of course means, I started all over again!)
Then in my joy of what seems like "Getting Closer", I drained the reservoir, sucked some air and....started over! Right now I have various positions I put the system in to get the air percolating out. One night the caliper on the floor to let any loops release their pesky air bubbles to the M/cylinder. Next day, caliper in vertical position. I have a piece of steel, same thickness as a brake rotor in between the pads so I can old school bleed with the hose/brake pump method.
Maybe today.....

Yes, you can't ignore the reservoir level while you're bleeding.
An important lesson that's been self-taught to thousands of Airhead owners !! 😆

1. Is the gold op lever on the master cylinder coming all the way back after EACH lever pull ?? While bleeding is in progress, there should be a tiny amount of free-play to allow this.
2. Are you seeing the "Champaign bubbles" at the reservoir ?? As long as you see bubbles... then you are NOT finished.
3. If you buy a new garage "oil squirt can" or large animal syringe, which you can fill with brake fluid and then push the fluid from the bleed nipple, up through the system. Since the air tends to naturally race ahead of the rising liquid fluid level, this sometimes works better for some people.

This guy explains pushing brake fluid in pretty good
https://www.youtube.com/watch?v=6UCNWfA7dVs

This lady doesn't explain anything, but she's fun to watch
https://www.youtube.com/watch?v=pJqk1bC0eGo

The ATE brake sucks, not to put too fine a point on it. BMW abandoned them in favor of the Brembo, then still had trouble getting the MC/caliper piston ratios correct.

The ATE caliper is a single piston sliding type but it swings rather than sliding. The swing must be set correctly. There is a cam surface on the pivot rod and turning the rod adjusts the swing. Procedure in your manual. I have just that section of the manual for a 90/6 if you do not and you can have it, I will never own an ATE again.

When the system is fully bled the lever should be firm. A wobbley mentioned the cable system introduces slop. It will never be rock solid from the first pull.

Going from a modern brake bike to an ATE bike can be hazardous. When I got a K100 I initially grabbed the brakes like I did on my airhead. Big mistake that almost landed me on my nose.

I am building up an '88 that has dual Brembos but they are conneceds by a hard line that arches up under the fender creating a high spot between them. BMW cheeping out again. I can see where it is going and am reverting the system to dual full lines rising to a splitter under the tank. This bike has a MC on the bars but of course it is the wrong size and the lever comes right back to the bars before the brakes apply so that will need correcting too, at loss of some braking power.

In case you are still fighting this, I just went through a similar scenario. I could not build any pressure and get anything out of the bleed screw, even with my pressure tank at 15 psi. It seems someone had a problem bleeding the system, so they tried drilling out the opening. Well, the broken drill bit IN the fitting says they didn't fix it. So I got another bleed screw and started again. Still nothing. Tore down the MC again--adding fluid and pushing arm got a spit of brake fluid from the outlet. Reassembled and still nothing, though there was fluid at the caliper. So I opened the fitting slightly--and got bubbles! So there's still some problem in the passage to the bleed screw which will require additional investigation in the future. But for now, new pads and steel brake line, rebuilt master and caliper, means I have good brakes.

Not sure if I'm still fighting this brake issue or not.... I have a LOT more brake now than when I wrote the original note. But.... I take it up to around 25-30mph here in the sub. grab 4 fingers of brake and squeeze for all I've got. It stops kinda hard but won't skid the front wheel. It's been 15 years since I rode this bike. Would it EVER skid the front wheel? Don't know if I ever tried. I KNOW I never NEEDED to. Maybe it is better than new for all I know. I am the original owner so I know no one has been at it with a drill or ??? It's got a steel line on it now, sleeved master cylinder, new seals in calipers and M/cylinder. new pads and scotch brighted rotor. What's the consensus out there? Can a single disk, R80/7 skid the front wheel? If so.... I still got work to do.

no, it will not. When you apply front brake hard the weight of you and the bike pitches forward loading the front tire and unloading the rear tire. This gives the front a whole lot of traction. If the surface is bad (wet, gravel, etc.) the front can slide out and if you are using some of your traction for cornering you can land on your nose. The rear end on the other hand is light and will slide out easily. The brake is not strong enough to do a 'stoppie" (lift the rear tire off the ground).

The next step in making the brake stronger is making your hand stronger. Try a Dynabee.

I agree with Arni. One of the advantages of the disk over the older drum design was that they tend to have greater stopping power without the fear of locking the wheel. From a physics point of view, you only get stopping power and/or steering control when the wheel does not lock. Or stated in the reverse... for maximum braking, the wheel MUST continue to rotate, albeit at a slower rate. Besides, why would you ever want to put flat spots (which would be the natural consequence of wheel-locking) on a tire ? If the wheel does lock, then then you instantly loose ALL ability to steer and brake. At that point it's much more likely to slide out from beneath the bike, that is to say... throw you onto the ground.

This is the whole point of ABS. It pulses the brake On/Off so that the wheel DOES continue to turn. In this way the driver DOES continue to have control over the vehicle.

Beyond that... your new pads haven't had time to fully seat. Come back in another 500-1000 miles and bleed, adjust the pivot position and check over the front brakes again. I think you've done a great job, but maybe looking for 100% a little too early.

So arni... You are saying that a "normal" performing single front disc brake WILL NOT be capable of locking the front tire?
I'm fully aware of front tire traction, stoppies, etc. I road raced various bikes for 28 years. Non of those race bikes had traction control but were all capable of skidding the front wheel (or a stoppie) if you were dumb/crazy enough to try it.
I figured my rock hard, 15 year old tires on this R80/7 would skid at 25mph and I'd be somewhere near the max capabilities of this braking system...
But no matter how hard I yanked it wouldn't happen (4 finger death squeeze...at least MY death squeeze!).
I do not expect this old gal to stand on it's nose with one finger like more modern bikes I have ridden. I'm just trying to find out it's max. Maybe I'm there? shorter stopping distances is always more betterer, but I'm wanting to leave it as stock as it was when I bought it in '78 so I'm not willing to put on another disc or ????
Thanks for your comments!

Brad

the single disk ATE brake will not lock the front on good pavement in my experience. Neither will the dual disk Brembo setup on the dual shock bikes. The brembos on the mono-shock bikes, maybe. To be determined. But it looks like those have other problems.

The ATE is a single puck swinging caliper. Even when carefully adjusted the pads have to wear to their optimal wedge shape. Takes awhile. Then the brake is merely adequate.