100% Biker & Trike Magazine Forums

Go Back   100% Biker & Trike Magazine Forums > 100% Biker > The Workshop

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 19-07-2015, 03:52 PM
Strider Strider is offline
Billy No Mates (only virtual ones!)
 
Join Date: Jan 2005
Location: Little Lever, Bolton
Posts: 1,179
Default Braking puzzler

We've been out on the bikes this afternoon, me on the sons CBR600 to check its ok after doing a bit of work on it and the other half on her GSX750F.

On the way back down the motorway we going to turn off and she went sailing past, waving her hands at me Turns out, when I got home she was there, her back brake had stopped working when she was on the motorway, so less brakes than she expected, so she came back the "slow" way.

As she had turned into the estate the brake was back, as if nothing had happened.

Now this happened about 3 weeks ago when I was with her, everything ok and we turned into where the meet was and nothing. The pedal was straight down to the stop, no pressure at all, almost as if the all the fluid had gone or the connection between piston and brake pedal had broke.

Ok, we'll have a brew and then take our time going back home, finished the brew and couldnt see anything obvious, I pressed the lever and hey!! everything was back to normal and has been until today.

I'm completely stumped, theres plenty fluid in the reservoir, ideas anyone????
__________________
When shit hits the fan, I've learnt it will not be evenly distributed !!!!
Reply With Quote
  #2  
Old 19-07-2015, 05:11 PM
strima's Avatar
strima strima is offline
Type like a Twat Me...
 
Join Date: Jul 2008
Location: St Neots, with the pointy heads...
Posts: 957
Default

Could be the seals in the master cylinder getting a little tired. I would overhaul the whole back brake system.
__________________
The best part of you ran down the crack of your mothers arse!!!
Reply With Quote
  #3  
Old 19-07-2015, 09:02 PM
harry's Avatar
harry harry is offline
Techno Guru! He's Good! He Knows Everyfink!
 
Join Date: May 2005
Location: Taunton
Posts: 3,399
Default

Strima is right it could well be the master cylinder. The seals can go hard and then don't spread out and seal against the sides of the cylinder. If the cylinder lives somewhere near summat hot (The engine or exhaust) and this causes the metal cylinder to expand that could well be the problem.

A rebuild kit if you feel confident or a new cylinder if you don't.
__________________
si is does non opportunus vos postulo a maior pango
Reply With Quote
  #4  
Old 19-07-2015, 10:17 PM
Strider Strider is offline
Billy No Mates (only virtual ones!)
 
Join Date: Jan 2005
Location: Little Lever, Bolton
Posts: 1,179
Default

I could understand that if it stopped working and then worked again when it was cold ...... but it stopped working and then came back to normal while she was still riding it.

Plus in between the first time and today, there hasnt been any problems.
__________________
When shit hits the fan, I've learnt it will not be evenly distributed !!!!
Reply With Quote
  #5  
Old 20-07-2015, 07:19 AM
Friar Tuck's Avatar
Friar Tuck Friar Tuck is offline
Super Moderator
 
Join Date: Apr 2004
Location: Brothertoft, Lincolngrad!
Posts: 11,262
Default

Try replacing the brake fluid and rebleeding. The brake fluid may be getting old and some air is seeping into the system as well?
__________________
Does my belly look big in this?
Reply With Quote
  #6  
Old 20-07-2015, 07:22 AM
Friar Tuck's Avatar
Friar Tuck Friar Tuck is offline
Super Moderator
 
Join Date: Apr 2004
Location: Brothertoft, Lincolngrad!
Posts: 11,262
Default

Maybe the brake pipe or connection could be lose slightly, again failing intermittently. I'd try doing all these before replacing the master cylinder.
__________________
Does my belly look big in this?
Reply With Quote
  #7  
Old 21-07-2015, 10:09 AM
wurzel wurzel is offline
Billy No Mates (only virtual ones!)
 
Join Date: Nov 2006
Posts: 1,007
Default

Has fluid level changed if not no leaks? Also is the fluid very old, if it is and has got damp in I believe the boiling point drops dramatically and then you get bubbles as it boils which redissolve when the fluid cools (which it will in high speed air flow) which would explain the mystery recovery.

Taken from a cycling website but explains it well

http://www.epicbleedsolutions.com/bl...s-mineral-oil/

Last edited by wurzel; 21-07-2015 at 10:16 AM.
Reply With Quote
  #8  
Old 21-07-2015, 10:28 AM
Strider Strider is offline
Billy No Mates (only virtual ones!)
 
Join Date: Jan 2005
Location: Little Lever, Bolton
Posts: 1,179
Default

Nope no leaks and no level changes.

That sounds like a plan, I'll change the fluid and bleed the system and see what happens.
__________________
When shit hits the fan, I've learnt it will not be evenly distributed !!!!
Reply With Quote
  #9  
Old 22-07-2015, 02:03 PM
devon-tony devon-tony is offline
Lucky Wombling Bastard except when he's not Wombling, when he's just a Lucky Bastard
 
Join Date: May 2004
Location: Devonshire
Posts: 4,371
Send a message via AIM to devon-tony
Default

warped or loose disc?

can push the pads back further and then when you brake the first 1 or 2 presses are used up pushing pistons back out.
__________________
nowt of much use here
Reply With Quote
  #10  
Old 22-07-2015, 06:01 PM
Strider Strider is offline
Billy No Mates (only virtual ones!)
 
Join Date: Jan 2005
Location: Little Lever, Bolton
Posts: 1,179
Default

Nope, its a brand new disc and pads, only been on about 3 months.

If it was doing it every time she went out I could almost understand it, but she had been out a good few times inbetween the first time and this recent time and it has been fine.

Wurzels suggestion seems to be the only one that fits the intermittent problem, still havent done it yet, think it will have to wait until the weeknd now. But I will check the mounting bolts at the same time, just in case
__________________
When shit hits the fan, I've learnt it will not be evenly distributed !!!!
Reply With Quote
  #11  
Old 23-07-2015, 02:52 PM
MrSmith's Avatar
MrSmith MrSmith is offline
Chatter Box
 
Join Date: Jul 2005
Posts: 200
Default

Brake fluid only lasts about 2-3 years before it becomes hygroscopic.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 04:43 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.