2002 XII Rear Brake Power Brake?

[1966F100]

Just picked up this nice bike a week or so back. 42K on it and I listed what was done to it in my "Hello" post. New Galfer Teflon/SS hoses were put on at 27,700 miles, 2015.

What I ran into out of the gate is very soft rear brake to the point of not being useful.
Bought new EBC F85 pads to replace the sintered pads that were on it, they were at 50% of material left. Yesterday.
Pads went on nicely. Tried pedal and it had nice pressure and feel. Around 1"-2" and would get nice and firm.

Thought I was home free.
Started it up this morning to ride to work. 1 mile to a right hand yield turn so I pressed the pedal to reduce speed.
It's back to being super soft and it 'activates' the Headlamp light.

Got to parking lot. Turned bike off. Tried pedal with bike off and it's back to good pressure/feel. Fired it up later to go home, back to super soft.

So I am confused. Ideas?

[Scott-(Altoona, PA)]

I know from this forum and from personal experience the rears are a real pain to bleed. Some have had positive results with a tilt twist and standing on their head while bleeding but I simply bleed till I get all fresh fluid and accept that the rears are just a minimal percentage of breaking power anyway and rely mainly on the fronts. I typically only use the rears to maintain slow speed (turtle) when turning with throttle applied or while setting at a red light.
Sorry I've got nothing of value to offer but am anxiously awaiting to read what others suggest! Power brakes, hmmmmmmm!

[1966F100]

Thx for the info. Just weird to have solid pedal with motor off and next to no pedal with motor on. Makes you think of a faulty power booster or electric boosted brakes gone bad.

[SgtSlag]

As far as I know, there is no power to the rear brake, no pump, nothing but a manually controlled hydraulic piston system, similar to the front brake. I would suggest Speed Bleeders: they are a one-way valve; open to bleed, pump the brake handle, and fluid comes out with each squeeze, draining the reservoir. They make bleeding brakes/clutches an easy, one-man job. The only issue with Speed Bleeders, is they push fluid (and bubbles) downwards, against the direction the bubbles want to flow.

Your best method is to do a reverse-bleed. There are videos on YouTube how to do it. Basically, you employ a hand pump to push fresh brake fluid up the line, towards the reservoir, which allows the bubbles to go the direction they are inclined to go already. Sorry I cannot be of further assistance.

With regards to the rear brake supplying only 30% of your stopping power, that is only part of the picture. If you lead with the rear brake by 1/2-second, every time you brake, you will eliminate the front-end dive, the whole suspension system will be far more stable, and effective, increasing control (and comfort) while braking. Bottom line is that this procedure makes the whole bike stable during braking, making you, and your passenger, much safer. Learned it from a riding book, by one of the pro's in the industry, many years ago. Cheers!