Rear brake not working

I made a separate thread for this because I can't find a similar problem on the forums.

As I was test riding my 2000 before purchase, the brakes felt off to me (I'd never ridden a bike with linked brakes). So the front would grab toward the end of the lever travel (Half an inch from the bar) and if I hit the rear immediately after it would grab normally. If I hit the rear first it would also grab to towards the end and the front would feel fine (Almost as if the system was missing fluid).

After my friend dropped the bike (Brake lever not bent, visual inspection doesn't show anything tweaked), the rear stopped working and the brakes behave as if they're de-linked. If I put ALL my weight in the rear, it gives me about 5-10% of braking. Not even enough to keep the bike from rolling on a slight incline. Fluid looks fresh and is full, the front grabs fine. Not spongy or anything as if there was air in the system.

The only thing the manual suggests for this symptom is a faulty proportional control valve (PCV). Any suggestions on how to troubleshoot before I start tearing the entire thing apart?

 

FYI, although the brakes are linked, the front lines are separate from the rear and bleeding them is just like any other bike. The rear is close to normal non-linked braking systems until you get to the front SMC and proportional valve. Here the front has one piston in each caliper that is triggered by the rear pedal and one piston in the rear caliper that is triggered by the SMC that is at the front left caliper. There are 5 bleed points for the rear/linked system. One at each front caliper, one at the proportion valve and two at the rear caliper.

When I bought my 5 Gen, the PO didn't seem to know anything about maintenance, other than just topping off the fluids! The rear brake had two Pistons that were nicked and that was causing them to rub away at the dust seals and the rubber was gumming up the pistons. Essentially the rear brake was useless but the fronts were fine. I basically rebuilt the back caliper, new seals and pistons, then bled the system thoroughly and did it again when I replaced the lines with steel braided ones. Brakes work fine now, no issues with the PCV or delay valve (found on the right fork).

If you don't have the Honda Service Manual, send me a PM and I'll send you a link to a copy I have in my Dropbox folder. This manual is invaluable if you service your own bike. Also, if you plan on doing the brakes yourself, you may consider getting one of those one-way bleeder tools or a helper, as it's a little difficult to reach the bleed nipples and hold the rear pedal down. Not impossible, just difficult.

 

Thanks, I really appreciate the tips and offer for the manual! I actually got it from the PO on a flash drive.

Yeah I had a pressure bleeder for my cars but I seem to have either misplaced it or given it to someone. I'll take the rear caliper off today if I have time and inspect, if it looks fine its off to the store for another bleeder and I'll start tearing it down. Might as well order some SS lines and do the caliper seals if it comes to that.