I have non power brakes. With that said I had the same problem. The car would not stop without really standing on the brakes. I checked every thing, again. New everything. Well stupid me, I did not have the brakes adjusted enough and oh, when I checked the brake fluid in the M/C it was empty. I adjusted the brake until I felt a little drag and then backed it off just a little and I filled the M/C with brake fluid. The car stops just fine now. That's my story and I'm sticking to it.
Just might want to check it out