Previous in Forum: Tube Tyres into Tubeless Conversion   Next in Forum: WHAT IS THE SPEED OF THIS JET BOAT ?
Close
Close
Close
30 comments
Participant

Join Date: Sep 2011
Posts: 2

Motorcycle Front Disc Brake Problem

09/07/2011 12:42 PM

I have a strange problem happening with the front disc brake on my 1983 Yamaha Virago XV920.

On hot days, when the sun is pounding on the bike, the front disc brake caliper engages. It does not fully lock up, but it's applying lots of pressure. So much so that if I release the throttle I don't have to brake to stop. After riding a little while it begins to release, but not fully.

On cool days this is a none issue.

A little history: My front caliper did seize. I took it off and rebuilt it. Ever since then I've had this problem occuring on hot days.

Any ideas what may be happening?

Thanks!

Chris

Register to Reply
Pathfinder Tags: brake caliper disc Motorcycle
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

Join Date: Apr 2010
Location: Mid Western USA - The Corn Belt
Posts: 1439
Good Answers: 58
#1

Re: Motorcycle front disc brake problem...

09/07/2011 5:20 PM

Hi Chris,

Welcome to CR4.

Going on the assumption that your brake system is hydraulic, the only thing that comes to mind is air trapped somewhere in the system when you re-installed and bled the caliper.

However, if there was air trapped in the system, I would think that you would probably feel the sponginess in the brake.

I cannot think of any other element in the brake system between the handlebar mounted reservoir (assumed) and the caliper that would expand due to the heat.

When you rebuilt the caliper did you use Yamaha approved parts and procedures?

Are you sure you bled all the air out?

Does the brake feel firm or spongy when applied?

Something obviously changed since the rebuild.

Regards - KJK

__________________
The first 5 days after a weekend are always the hardest................................
Register to Reply
2
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#2

Re: Motorcycle front disc brake problem...

09/07/2011 6:20 PM

Why did it seize in the first place?

I think you may have to change out the flexible line leading to the caliper. I know this happens on other vehicles when the interior of the flexible line gets messed up. It won't allow fluid back to the master cylinder......................probably the same with bikes. The heat probably exacerbates the problem.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#15
In reply to #2

Re: Motorcycle front disc brake problem...

09/08/2011 4:52 AM

That's my take too.

GA

Somet5hing is preventing the liquid returning to the reservoir.

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42330
Good Answers: 1666
#3

Re: Motorcycle Front Disc Brake Problem

09/07/2011 7:20 PM

Hydraulic fluid may be incompressible, but it isn't immune to thermal expansion and contraction.

I know nothing about your bike, but I'll bet there's a check valve, or bleed valve that is either clogged or stuck. The brakes should release, with minimal drag.

I think entrapped air would have already put you in the ICU.

Check the plumbing and valves. Bleed the system, just in case.

Register to Reply
Guru
United States - Member - Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - RC Aircraft - New Member Engineering Fields - Aerospace Engineering - New Member

Join Date: May 2009
Location: Saint Helens, Oregon
Posts: 2214
Good Answers: 69
#10
In reply to #3

Re: Motorcycle Front Disc Brake Problem

09/07/2011 10:10 PM

Hi Lyn, I didn't see your post until after I posted #4. I was interrupted while I was writing it and you got there first. It seems like we were thinking along the same lines thou, with thermal expansion, you with ICU and me, being catapulted over the handle bars. I'm glad to see he's going to repair it before anything does happens.

__________________
Confucius once said, “ Ability will never catch up with the demand for it".
Register to Reply Off Topic (Score 5)
Guru

Join Date: Oct 2008
Posts: 42330
Good Answers: 1666
#11
In reply to #10

Re: Motorcycle Front Disc Brake Problem

09/07/2011 10:52 PM

You can't give too much good advice. Sometimes, it bears repeating.

Register to Reply Off Topic (Score 5)
4
Guru
United States - Member - Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - RC Aircraft - New Member Engineering Fields - Aerospace Engineering - New Member

Join Date: May 2009
Location: Saint Helens, Oregon
Posts: 2214
Good Answers: 69
#4

Re: Motorcycle Front Disc Brake Problem

09/07/2011 7:25 PM

You might try removing a little brake fluid from the reservoir,it sound like there's not enough air space in the reservoir for fluid expansion on hot days, fluid expanding thus applying the brake. Which would make sense after riding awhile(air cooling the fluid) they seem to release.

__________________
Confucius once said, “ Ability will never catch up with the demand for it".
Register to Reply Good Answer (Score 4)
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#5
In reply to #4

Re: Motorcycle Front Disc Brake Problem

09/07/2011 7:35 PM

Hey dj.

Not trying to be snarky. But we don't ever want air in a hydraulic brake system........................failure would be imminent.

Edit}}}Oops............you said reservoir. My bad. You may be right. It shouldn't be filled past the line on the side.

I would also park this bike until I had it fixed.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply
Guru
United States - Member - Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - RC Aircraft - New Member Engineering Fields - Aerospace Engineering - New Member

Join Date: May 2009
Location: Saint Helens, Oregon
Posts: 2214
Good Answers: 69
#7
In reply to #5

Re: Motorcycle Front Disc Brake Problem

09/07/2011 8:33 PM

Hey there Mark, hope you and your family have been able to keep your feet dry. Anyhow, I've seen similar problems with closed hydraulic systems that were over filled and not having enough room for thermal expansion. And being the brake pucks are the only thing that will move, they'll apply the brake. I'm surprised that he hadn't noticed his front brake being touchy or being catapulted over the handle bars! I, too, would park it until the problem is solved! DJ

__________________
Confucius once said, “ Ability will never catch up with the demand for it".
Register to Reply
Anonymous Poster #1
#28
In reply to #5

Re: Motorcycle Front Disc Brake Problem

09/09/2011 4:51 AM

moisture in the brake fuid will act this way but only if the fuid is above the boiling point of water.

Register to Reply
Power-User

Join Date: Jun 2009
Location: New Zealand
Posts: 403
Good Answers: 5
#30
In reply to #4

Re: Motorcycle Front Disc Brake Problem

09/09/2011 11:21 PM

Hi Dj95401

If this was the case, I would have to look at the breather on the main cylinder

Cheers

Joe

Register to Reply
Power-User

Join Date: Mar 2011
Location: Ground Zero of the Pompous and self important....Washington DC
Posts: 416
Good Answers: 8
#6

Re: Motorcycle Front Disc Brake Problem

09/07/2011 8:28 PM

There might also might be moisture in the system.....heat basically forcing the water to vaporize and pressurize the system. The fact it has seized indicates moisture was in it...and perhaps not completely eliminated.

Register to Reply
Guru

Join Date: Sep 2009
Posts: 1050
Good Answers: 88
#8

Re: Motorcycle front disc brake problem...

09/07/2011 8:55 PM

Correct piston rebound, enough to give a small pad-to-disk clearance when you release your brake, is normally forced only by rubber sealing ring's elasticity. But for this to happen, the piston itself should be able to slide freely (if rubber ring was not there). Obviously this is not your case, and since you don't mention any leak, sealing ring is likely (?) to be correctly positioned. What's left to blame is ruined piston and/or cylinder surfaces, possibly from an outer rubber boot rupture (common for unorthodox practices during pads change) and dust, debris and humidity inserting where it shouldn't, and causing this damage. This condition was to be addressed at your previous rebuilt. Now, I would do it again, after lightly honing the bore and verifying surface condition allows rebuilt. Safety and brake's wear because of this behavior alone, justifies the cost. S.M.

__________________
Life is complex. It has a real part and an imaginary part.
Register to Reply Score 1 for Good Answer
Participant

Join Date: Sep 2011
Posts: 2
#9

Re: Motorcycle Front Disc Brake Problem

09/07/2011 8:59 PM

Great info everyone. Thank you so much!

The bike is parked and I will pull the entire system apart again.

While I'm at it I think I'll replace the brake line too considering it is 28 years old.

I did inspect the cylinder and piston for damage and didn't see anything, but I will look more closely on the next rebuild.

I will report back in a couple of weeks with what I find, so it's all on record for others who might experience the same problem.

Thanks again,

Chris

Register to Reply Score 1 for Good Answer
Guru

Join Date: Aug 2010
Location: Melbourne, Australia
Posts: 740
Good Answers: 24
#12
In reply to #9

Re: Motorcycle Front Disc Brake Problem

09/08/2011 12:09 AM

Check the Master cylinder as well as the slave and brakeline.

Register to Reply Score 1 for Good Answer
4
Participant

Join Date: Apr 2011
Posts: 2
Good Answers: 1
#13
In reply to #12

Re: Motorcycle Front Disc Brake Problem

09/08/2011 1:07 AM

The classic reason for this problem you describe is failure to correctly set the "at rest" or retracted position of the master cylinder piston. The master cylinder piston at rest must retract past the port connecting the master cylinder with the fluid reservoir. If the master cylinder piston doesn't retract far enough to allow fluid to pass freely from the master cylinder to the reservoir then, when heat expands the fluid in the master cylinder, the pipe leading to the caliper and inside the caliper there is no relief of this increased pressure and the caliper piston pushes against the brake pads and actuates the brake.

It's a simple error repeated many times all over the world. I hope this is the case with your bike and an easy fix. Good luck.

Register to Reply Good Answer (Score 4)
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#16
In reply to #13

Re: Motorcycle Front Disc Brake Problem

09/08/2011 4:54 AM

GA

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4347
Good Answers: 131
#17
In reply to #13

Re: Motorcycle Front Disc Brake Problem

09/08/2011 7:19 AM

I was about to make that point but you beat me to it!

Somebody suggested a check valve in the circuit, but if there were one the brakes would stay on once applied, not a good idea.

Codey

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Hobbies - Musician - New Member United Kingdom - Member - New Member

Join Date: Mar 2007
Location: England
Posts: 950
Good Answers: 48
#18
In reply to #17

Re: Motorcycle Front Disc Brake Problem

09/08/2011 7:30 AM

It is not uncommon to have check-valves in brake circuits (aka 'Residual Pressure Valves'), there is one in my wife's old Beetle. They are usually located in the master cylinder. They usually allow a small amount of backflow to relieve the main pressure, whilst maintaining enough residual pressure to ensure pedal travel is not excessive. I'm not sure that this arrangement would be required on a motorcycle, and even if it were I'm not sure this would be the cause of the problem in this instance.

__________________
brianparker007@hotmail.com
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4347
Good Answers: 131
#22
In reply to #18

Re: Motorcycle Front Disc Brake Problem

09/08/2011 12:14 PM

That's right, there are sometimes valves in the circuit, eg in the original Mini there was a valve to limit pressure to the rear brakes, to try to prevent wheel lock. I just meant there couldn't be a check valve to completely stop reverse flow or there'd be a problem.

I think Envelope Guy may have hit on the answer. Many years ago I worked on a Land Rover with adjustable master cylinder pushrod. The pedal travel had increased and some misguided soul tried to cure it by extending the pushrod. Result - brakes binding.

Codey

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Popular Science - Weaponology - New Member Safety - ESD - New Member Hobbies - Fishing - New Member

Join Date: Sep 2006
Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E
Posts: 17996
Good Answers: 200
#24
In reply to #22

Re: Motorcycle Front Disc Brake Problem

09/08/2011 1:45 PM

Many cars have a pressure reducer for the rear brakes. Most are linked in some manner, to the ride height of the rear suspension, the heavier the load, the lower the rear end, the more pressure is sent to the rear brakes....but this valve does not prevent fluid returning once the foot is off the pedal.....

It just prevents lightly loaded rear wheels from locking up.....

You can read more here:-

http://www.familycar.com/brakes.htm

Look for:- Proportioning valve or Equalizer Valve

__________________
"What others say about you reveals more about them, than it does you." Anon.
Register to Reply Score 1 for Off Topic
Guru
United States - Member - Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - RC Aircraft - New Member Engineering Fields - Aerospace Engineering - New Member

Join Date: May 2009
Location: Saint Helens, Oregon
Posts: 2214
Good Answers: 69
#23
In reply to #18

Re: Motorcycle Front Disc Brake Problem

09/08/2011 12:54 PM

Hi Holzfeller, the 'check valves' are actually proportioning valves, that limits the amount of pressure applied to the rear brakes, to help prevent them from locking up during heavy braking. Codemaster is correct #22, there is no check valves in automotive braking systems.

__________________
Confucius once said, “ Ability will never catch up with the demand for it".
Register to Reply Score 1 for Off Topic
Guru
Hobbies - Musician - New Member United Kingdom - Member - New Member

Join Date: Mar 2007
Location: England
Posts: 950
Good Answers: 48
#26
In reply to #23

Re: Motorcycle Front Disc Brake Problem

09/09/2011 3:43 AM

Hi dj95401. What I am referring to is not the same as the proportioning valves or pressure reducing valves you often see. It is a check valve, in fact, to be precise, it is a double or two-way check valve, although VW refer to it as a 'Residual Pressure Valve'. Its' purpose is to maintain a residual pressure in the brake circuit when the pedal is released in order to avoid excessive pedal travel when the brakes are re-applied. Here is a diagram:

As you can see, if the main valve was seized the pressure in the brake circuit would not be relieved.

__________________
brianparker007@hotmail.com
Register to Reply Score 1 for Off Topic
Power-User

Join Date: Mar 2011
Posts: 259
Good Answers: 6
#19
In reply to #9

Re: Motorcycle Front Disc Brake Problem

09/08/2011 9:05 AM

If I'm corrrect, as I also own a Yamaha motorcycle, the master cylinder has an adjustment screw for the lever that contacts it's piston. If that screw is turned too far in, it pushes the piston past the point where it will allow the fluid to go back into the reservoir. Check that as well.

Register to Reply
Associate

Join Date: Apr 2011
Posts: 33
Good Answers: 2
#21
In reply to #9

Re: Motorcycle Front Disc Brake Problem

09/08/2011 11:09 AM

I have another idea. Get rid of the Yamaha altogether. I had a 1981 Special 650. Once parts started failing when the bike was about 6 months old, they never stopped. I finally sold it for scrap. I'll never have another Yamaha motorcycle!

Register to Reply Score 1 for Off Topic
Associate

Join Date: Mar 2011
Posts: 48
#14

Re: Motorcycle Front Disc Brake Problem

09/08/2011 3:10 AM

Hi There,

I ride motorcycles and do all of my own maintenance barakes and all. Firstly when you rebuilt your caliper.. Did you take out the caliper seals? Did you clean out the seal grooves? There is nearly always a build up of corrosion (I live in the uk so get road salt corroding the seal grooves) or dirt( Brake dust etc from dry environments) under those seals . If you did not cleans them up then just fitting in new seals was a waste of time and money. Also did you put any grease on the seals to get the piston back in? If so bad move.. grease swells the rubber on brake seals. Use a little bit of brake fuild to lubricate the pistion and seals and it should pop in (Provided you have cleaned out the seal grooves)

However if this only happens on hot days then it may be down to fluid expansion .. as i have lived in africa with very hot temperatres with bikes with disc brakes i never experienced this problem.

Maybe a good idea to strip out the caliper and clean everything, also replace all the fluid with new and rebleed it all. Maybe worth the effort to also replace the rubber brake line with a new braided brake line ,many brands available out there.

It may also be worth the time and effort to strip your master cylinder and clean that out and fit a new kit in there too. Some of the master cylinders also seem to get a blockage when the fluid is very old and seems to "crystalise or get gummy particles form) and the ports get gummed up. And what maybe happening is that as the temperatures rise, the fluid may expand enough to block a port from returning the fluid bake to the reservoir.

Good luck.

Register to Reply Score 1 for Good Answer
Associate

Join Date: Jun 2011
Location: leighton Buzzard
Posts: 32
#20

Re: Motorcycle Front Disc Brake Problem

09/08/2011 10:11 AM

Hi Folks,i have had a fair amount of experience on these and i would go for dirt in the master cylinder or the clearance being wrong on the at rest setting as RWC suggests ,the master cylinder piston only has to restrict the return orifice slightly and the system will "pump up" and i suspect is made worse by some of the temperatures you guys get.Check the clearance between the Screw end and the piston and set it to just above factory minimum(wider gap)if you have the information or @ half a turn back (remember to re tighten lock nut)and see if re occurs.Don't forget to get used to where the brake starts to bite before riding,it won't be a lot different but enough,this should cure it as long as the caliper hasn't re siezed.Ride Safe T

Register to Reply
Participant

Join Date: Sep 2011
Posts: 1
#25

Re: Motorcycle Front Disc Brake Problem

09/08/2011 3:33 PM

Check to see if you have a vent hole that is plugged in the master cylinder. Change fluid out and bleed using DOT 4 fluid

Register to Reply
Anonymous Poster #1
#27

Re: Motorcycle Front Disc Brake Problem

09/09/2011 4:43 AM

i'ld check the relief valve in the master cylinder. make sure the brake "puck" is not stuck in the cyinder. try pushing it back in with a c-clamp. check for corrosion in the cylinder. comments are also good advise.

Register to Reply
Anonymous Poster #1
#29
In reply to #27

Re: Motorcycle Front Disc Brake Problem

09/09/2011 4:57 AM

sorry guys, it's already been said.

Register to Reply
Register to Reply 30 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Andy Germany (3); Anonymous Poster (3); Codemaster (2); dj95401 (4); Envelope Guy (1); Holzfeller (2); Joe Sparky (1); jordan (1); KJK/USA (1); kramarat (2); lyn (2); Mike Davis (1); RWC94303 (1); SimpleMind (1); simspace (1); Smoothy (1); taurus66 (1); tonyu (1); WAWAUS (1)

Previous in Forum: Tube Tyres into Tubeless Conversion   Next in Forum: WHAT IS THE SPEED OF THIS JET BOAT ?

Advertisement