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OldFart

Brakes Drag When Hot...Big Time!

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I just picked up a 1998 VFR800 two weeks ago and today the brakes virtually locked up on me as I was pulling into my drive after a long hot ride.  I say virtually as I was able to use the motor to muscle the bike up the drive but the brakes were so tight I could not push the bike in any direction without engine power.  (At this point I am realizing that I should have tried to get it on the center stand so I could tell if it was one wheel or both, duh!)  As they cooled they gradually released a bit. I had noticed on earlier rides a little dragging after a ride but assumed that was normal as I have had the same feeling with other bikes, and today it was way worse. I have the mechanical sense of a 9 year old girl so any help or advice would be much appreciated!  

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Probably something to do with the linked brakes and the secondary master cylinder or proportioning valve.  Time for a fork swap!

 

Ciao,

 

JZH

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57 minutes ago, JZH said:

Probably something to do with the linked brakes and the secondary master cylinder or proportioning valve.  Time for a fork swap!

 

Ciao,

 

JZH

Ahhh...any other suggestions?

 

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You really don't provide any information that is useful for diagnosis other than brakes not releasing.

 

If it was me, and things were locked up I would:

  • Determine if the symptoms are universal, rear only, front only or (if you have the ability) front left, or front right
  • Depending on which, systems were affected, I would start at the master cylinder(s) for that system and crack open the lines to see if the calipers release
    • If they do release, rebuild that master cylinder
    • As mentioned above, the linked system bikes have multiple master cylinders and a proportioning valve that isolates the systems.
  • Work your way down the system to the caliper to see if the affected calipers release
    • I once had a girlfriend who had a car with a bad hose at the wheel that functioned like a check valve and would not release the caliper
  • If cracking the system doesn't release the affected calipers, investigate the pins that allow the calipers to float
  • If the pins are floating, investigate the pistons in the calipers for cleanliness.  (This is actually the most likely cause, but not where I would start)

Your best bet would probably be to just do a system rebuild since you don't know the history.  (The bike is 20 years old and needs it anyway)  In the great scheme of things, brakes are very forgiving to abuse and it takes quite a bit of neglect for them to fail. 

 

Be honest with yourself, if you don't have the mechanical skill to do this take your motorcycle to a competent mechanic.  

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Moisture causing the pistons to expand from the heat? Time to change fluids and inspect calipers and master cylinders. Maybe.


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Stop, Wait, Hold on for a moment... there might be a really easy, simple explanation for this situation.  And it's an easy thing to check (just by looking at the front brake lever on the right handlebar)

 

When people mess with the front brake lever on the VFR800 (like when they take it off to service/rebuild the front brake master cylinder) they sometimes put the plunger in backwards.  I'm talking about the golden-colored piece of metal that transmits your hand-force between the "cup" on the inside of the front brake lever and the front brake master cylinder piston.

 

When this piece is installed backwards it sets up a situation where the pressure from braking the bike cannot properly bleed off when you release the brake lever, so the pressure builds up (bit by bit) and locks the brake just as you described.

 

I'm referring to part number 13 in this picture.

Screen%20Shot%202018-09-13%20at%207.04.1

 

 

If it's properly assembled it will look like this:

 

IMG_20180913_185930_zpsdyfjkvmp.jpg

 

You will be able to see the tapered portion of the part.  If it is installed backwards you won't see any taper on the part.

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Outstanding.  I will check it first!  Thanks, Bill

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