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Builder630
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« on: May 21, 2014, 04:38:34 PM » |
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Serviced the rear, wheel bearings, final drive, shock bushings, u-joint, etc. put it back together and brake problems. Fealt spongy so I bled the caliper. Noticed one piston worked quicker than the other so I removed tge caliper, took out both pistons and cleaned n polished them. Cleaned out caliper, removed piston seals and cleaned them. Bled the master cylinder and caliper and same problem. Seems to flex when I press the brake but doesn't grab fully so weak brake. It doesn't detract completely either which leads to a hot rotor. If I disconnect the caliper and press the pads against plywood it's a strong grip..... I'm lost here. I just ordered new seals just in case. I've taken these out and reinstalled them so many times already I can SERIOUSLY do this with my eyes closed. Any ideas?
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N8171S
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« Reply #1 on: May 21, 2014, 04:52:56 PM » |
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When you get your new seal kit remove the old rings. I am sure you will find white corrosion behind the outer dust seal. I bought a small rotary brush for my dremel tool to clean this crud out. I found it on every caliper on both of my valks. The corrosion puts pressure on the o rings that makes them stick. Do all the calipers. That would be a wire brush, around $3.95 at home depot. Good luck, Barnstormer
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Builder630
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« Reply #2 on: May 21, 2014, 05:17:20 PM » |
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N8, do you think a slow piston would make the other work harder causing uneven pressure thus the binding?
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PAVALKER
Member
Posts: 4435
Retired Navy 22YOS, 2014 Valkyrie , VRCC# 27213
Pittsburgh, Pa
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« Reply #3 on: May 21, 2014, 06:33:26 PM » |
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When you clean/rebuild the caliper... Spray brake cleaner in thru the valve body and even use compressed air, and maybe if need be and you have a small enough diameter wire run it thru to chck for clogs/blockage.
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John  |
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hubcapsc
Member
Posts: 16785
upstate
South Carolina
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« Reply #4 on: May 21, 2014, 06:40:50 PM » |
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You had it all the way apart, cleaned it and put it back together...
I guess when you pushed the pistons back in after you refurbished the
caliper, they both readily went all the way in, as in pretty much disappeared
into the caliper body?
I had a caliper once where one piston could get "cockeyed" when I
was pushing it in (after refurbishment), and it would wedge up. I had
to tap it in with a little brass hammer. Later, when in use, it wouldn't
release fully, it would drag and the rotor would get hot. I should have
ditched that caliper when I noticed it wasn't right as I was refurbishing
it. Often good calipers can be had from Pinwall for around $35...
Hopefully yours can be made good with cleaning...
-Mike
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Builder630
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« Reply #5 on: May 22, 2014, 09:39:00 AM » |
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Pulled it apart yet again, removed the calipers, seals, etc. cleaned the caliper and scrubbed the seal ridges with brake cleaner. Blew out everything with compressed air, coated the seals with fresh type 4, reinstalled everything, greased the pins, bled it..... Same problem. FRUSTRATING.... If I had an air leak somewhere it should leak fluid at compression. Maybe it's the feed to the master cylinder from the resevoir.... Perhaps a loose hose fitting pre master cylinder?
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hubcapsc
Member
Posts: 16785
upstate
South Carolina
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« Reply #6 on: May 22, 2014, 10:55:41 AM » |
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Perhaps a loose hose fitting pre master cylinder?
I think you'd see brake fluid coming out of anything that was loose...
-Mike
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hubcapsc
Member
Posts: 16785
upstate
South Carolina
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« Reply #7 on: May 22, 2014, 11:02:20 AM » |
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This didn't cause spongyness, just a heated rotor... and it probably would have been good soon enough... but...  Cleaning the pin that the pads slide on is important... the new pads will sit on a different, and dirty, place than the old pads were on... -Mike |
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Ricky-D
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« Reply #8 on: May 22, 2014, 11:40:39 AM » |
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There is nothing in the system that makes the pistons move evenly.
Only when the pads contact the rotor is piston alignment achieved.
The true test would be upon releasing the brakes.
There will be some rubbing, but no dragging to any extent.
The rotors naturally get hot from brake application.
If you think the rubbing is heating the rotors:
Ride the bike using only the front brakes.
If there is very little heat in the rotor, there is no problem.
***
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2000_Valkyrie_Interstate
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Rio Wil
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« Reply #9 on: May 22, 2014, 12:20:34 PM » |
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There is nothing to retract the pads, they will (as Ricky says) rub the rotors slightly. Part of the sponginess you feel in the brake pedal might be in a rusted up pivot bolt in the rear brake pedal....
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8Track
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« Reply #10 on: May 23, 2014, 12:34:12 AM » |
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Maybe the tiny return hole in the master cylinder is partially blocked?
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quexpress
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« Reply #11 on: May 23, 2014, 06:50:00 AM » |
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Check the hose between the caliper and the master cylinder. I had a similar problem on a car a lonnnng time ago. Inexperienced ... I changed the whole caliper for a new one only to later find out that the hose was blocked.  |
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I still have a full deck.
I just shuffle slower ...
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