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Discussion Starter · #1 ·
Hi all,
First time posting on a forum out of pure desperation. After doing a pad change and cracking the bleeder to move the pistons back I've lost pressure on my rear brake. The pedal behaves like it has no fluid in it. I have the service manual and I've tried to bleed using the correct procedure, I've tried endlessly with a vacuum bleeder, I've checked seals in the calipers, I have no leaks anywhere in the system. When bleeding with a vac bleeder all it achieves is sucking the lines dry of fluid. It doesn't seem to ever drain the reservoir. I've reverse bled the system from the front, but it gets to a point where I'm pressuring the line to the extent that it begins to move the pistons in the rear, but fluid never starts to fill the reservoir and the pedal remains useless.
I've been a mechanic for four years, I've worked on a lot braking systems, the bike has been to two independent garages and both times I've been told they don't know what the problem is. It's booked in to a Honda main dealer in a months time but they don't have the best reputation and im already financially down.
If anyone has any ideas they would be greatly appreciated.
 

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First, Welcome to the forum @MD2021 !

Be aware that the center piston on the left front caliper is linked to the rear brake system and that bleeder must be closed to bleed the rear portion of the rear brake system. But it sounds like you know this already. I also think this sounds like another of many such cases on a few bikes I've had experience with. You may have an air blockage somewhere in the line. The flag on your avatar would indicate that you definitely have an ABS/TC version of the bike. Only in the USA is there a version that does not have ABS so no need to go there. It is possible that the blockage is in the ABS pump. That seems to be where air blocks are particularly stubborn. This, and the reminder to close the front bleeder, comes from your statement that you can bleed the lines dry yet the reservoir (cylindrical can located above the main foot pegs and behind the engine cylinders on the the right side) is still unaffected and stays full. Perhaps what I've heard about may work for your situation... fix the rear brake pedal as far down/on as possible and let it sit overnight to perhaps get the air bubbles to migrate.

Another possibility, but really not very common, is that the ABS pump is defective and the valve is frozen closed preventing any brake action at the calipers. Like I've said, this is something I've read and heard about from others but have never actually known it to happen, except maybe once but not on anything of mine.

I've bled my own front and rear brakes on my CTX1300 Deluxe (with ABS/TC) and found that I had to rebuild the rear master brake cylinder by replacing the piston and seals. That was a job and a half since I did it without removing the master brake cylinder and fixed it in place on the bike. Had to modify my cir-clip tool to get around some of the bike frame so I could remove/replace that part. One of the issues was getting the rear lines to bleed all the air with the one bleeder up front and 2 on the rear caliper. Other than the defective seals in the master cylinder I also found out I was using a bleeder adapter that was just a bit too big for the bleeders on the bike so was just sucking air with my vac bleeder. Once all that was handled it all worked out great.

I've been doing much of my own bike maintenance for the last 18 years and have done much of the repairs on my other vehicles for over 20 years before that... starting with a carburetor rebuild on an old Buick Skylark (was made a little easier by sitting on top the engine while working on that one).
 

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Discussion Starter · #3 ·
Hi Bob,
Sincerely appreciate your lengthy and detailed response.
As you mentioned with the abs unit I have been considering whether that would be a problem, as you said it explains why the pedal and the brake line behave like theyre on separate circuits and why I can't draw fluid through. However given what I've done to the bike I simply cannot believe that I would of caused damage to it (And if I have that's going to be a very expensive and incredibly unlucky mistake.) The rear brake was absolutely fine and I've since ridden the bike up the road to see if the abs light goes out and it does.
Then my mind turns to the master cylinder, the only thing I had done around that area was lubricate the pivot on the pedal because it was sticking. This involved moving the pedal up and down rapidly and depressing the pedal further than usual. If that has damaged a seal in the master cylinder then surely I would be seeing fluid leakage? And even if I wasn't I would still be getting fluid through, maybe even building pressure before It slowly loses it. But that doesn't happen.
This problem seems to have gone from a simple brake bleed to an absolute nightmare. One of the garages I took it to said they had tried to bleed the abs modulator but had no luck with that.
At this point I've even reached out to Honda themselves for technical assistance but they tell me they only offer that to their dealers.
 
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