front brakes, master cylinder?
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Cruiser
Joined: May 2011
Posts: 140
Likes: 0
From: UK
front brakes, master cylinder?
Hi everyone, need some advice.
Managed to find a nice set of chrome hand controls for my 1995 RK and everything works great...... except the front brakes. After fitting the clutch lever and both switch housings i got round to swapping the brake lever/master cylinder over. I cant get any front brake??? Ive bled the thing until i ran out of new fluid. Is it possible the master cylinder is drawing in air when i pull the lever? wouldn't i see leakage from here if that was the case?
Thanks in advance
Managed to find a nice set of chrome hand controls for my 1995 RK and everything works great...... except the front brakes. After fitting the clutch lever and both switch housings i got round to swapping the brake lever/master cylinder over. I cant get any front brake??? Ive bled the thing until i ran out of new fluid. Is it possible the master cylinder is drawing in air when i pull the lever? wouldn't i see leakage from here if that was the case?
Thanks in advance
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
1.) is the master cylinder made for twin brake?
the bore and stroke would have to be the same to provide sufficient pressure to the calipers.
2.) air problem IF you see air bubbles in the reservoir or bled fluid
mike
the bore and stroke would have to be the same to provide sufficient pressure to the calipers.
2.) air problem IF you see air bubbles in the reservoir or bled fluid
mike
Thread Starter
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Cruiser
Joined: May 2011
Posts: 140
Likes: 0
From: UK
Hi Mike.
Yes it is for the twin disc model, when i was bleeding the brakes i just couldnt get a steady flow without air bubbles? It was as if the air was appearing quicker that it was leaving
Lee
Yes it is for the twin disc model, when i was bleeding the brakes i just couldnt get a steady flow without air bubbles? It was as if the air was appearing quicker that it was leaving
Lee
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
must be a bad or missing seal in the master cylinder
if H-D, maybe the chroming is keeping the seals from seating or have damaged the seals-- looks like a rebuild---
do you know how to "bench bleed" a master cylinder?
removed from bike, you direct the hose to the reservoir and work the master cylinder until it flows completely clear of air bubbles.
work the lever slowly and completely with each stroke, slow so that aerated fluid is not pumped through.
If you cannot get clear fluid then the master cylinder is the problem
If that checks ok, then you chase the problem from top to bottom.
use clean bleed lines and a clean container so you don't go through gallons of fluid ( and you have the correct fluid for your system?
mike
if H-D, maybe the chroming is keeping the seals from seating or have damaged the seals-- looks like a rebuild---
do you know how to "bench bleed" a master cylinder?
removed from bike, you direct the hose to the reservoir and work the master cylinder until it flows completely clear of air bubbles.
work the lever slowly and completely with each stroke, slow so that aerated fluid is not pumped through.
If you cannot get clear fluid then the master cylinder is the problem
If that checks ok, then you chase the problem from top to bottom.
use clean bleed lines and a clean container so you don't go through gallons of fluid ( and you have the correct fluid for your system?
mike
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
Can't see how damaged seal in master cylinder allows air in as long as reservoir is topped up. If you were not building up pressure AND not seeing air I would agree.
Sound to me like your bleeding process is not right, study that and make sure you understand it fully. Nervous about teaching you to suck eggs
Sound to me like your bleeding process is not right, study that and make sure you understand it fully. Nervous about teaching you to suck eggs
Thread Starter
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Cruiser
Joined: May 2011
Posts: 140
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From: UK
I re-bled the front brakes again today. The best i seem to achieve is about two thirds pressure against what it was before the change over. When i try to improve this i find all the pressure goes again and im back to square one. Oh well, winters here got plenty of time to sort it
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Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
Is there still air in the system? If so, keep bleeding, if not the seals in master cylinder would be my suspicion. If it were seals in calliper you would see external leak
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Cruiser
Joined: Oct 2008
Posts: 114
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From: new jersey
I had a real crappy front brake. Bleed the fronts and found out there where 2 pistons not touching the pads(4 piston) calipers. Rebuilt the calipers and they where fine after that.Maybe the a couple pistons retracted back in the caliper.
Try pulling the lever 4 or 5 times real quick. If you get a good pressure then a piston in not out of the bore. Worth a try.
Try pulling the lever 4 or 5 times real quick. If you get a good pressure then a piston in not out of the bore. Worth a try.
Thread Starter
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Cruiser
Joined: May 2011
Posts: 140
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From: UK
Thanks everyone for your feedback and generous advice. I got it back up to around two thirds pressure again last night and decided to leave it untill today to have another go. I left the top off the master cylinder over night as i was going to resume this morning. It turns out whatever air was trapped in the lines found its way out through the master cylinder over night, before i started i pumped the lever 3-4 times and it firmed up to where it was before!!
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