Unknown Brake Issue

Discussion in 'Mechanics Garage' started by David Arias, Dec 4, 2019.

  1. David Arias

    David Arias New Member

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    Hi guys I was hoping someone could point me into the right direction as to what I messed up on my bike.

    A little information about my bike:
    2004 VFR800 Non-ABS
    Around 26,000 miles.

    Starting about two months ago my brake pedal started to feel mushy. Slowly and slowly I lost rear brake power until I no longer had any fluid in the reservoir. The front brake still worked fine besides this knock I would hear when braking at low speeds (presumably from the left caliper, the linked one). I rode like this for about a month and two weeks.

    Two weeks ago I swapped all the brake lines on my motorcycle with the Galfer Kit that I had bought. After about 10 hours of work disassembling the bike bleeding the lines etc. I finally put the bike back together and went for a ride. First thing I noticed is that under my seat I started to see steam, and when I went to pull the brakes the bike almost bucked me off. I felt a clunk and then the bike violently applied the brakes or otherwise stopped me in some fashion. I pulled over and noticed fluid leaking from the rear PCV Valve.

    Knowing that these bikes from this year suffer from PCV failure issues, I contacted Honda warranty and they told me to bring the bike in to a Honda Franchise Dealer. If they determined that the failure was caused by a defective PCV valve, they would cover the cost. At the time I did not know whether the bike trying to buck me off or not was related to the PCV valve as I didn't and still don't exactly know what it does.

    As I rode/ walked my bike to the dealer that was just a mile away with my hazards on I noticed that my speedometer was not working. I remember removing the sensor to be able to replace the clutch line. I thought perhaps the bike was trying to throw me off because I had misaligned the speedo sensor on the sprocket and it had shattered and now pieces of the sensor wheel were mashing about in the crank case cover. I could not verify as when I dropped the bike off at the dealer I didn't have the tools to take the speedo sensor off the bike and take a look.

    Honda ended up covering the cost of replacing my PCV valve and apprehensively I rode my bike home.
    Before leaving the dealership I took a look at my speedo sensor, and on verifying that it was just a little loose, I tightened it and I started getting a reading on the dash once again.

    About 3/4 of the way there I noticed my brakes felt different. They felt heavy, as If I pressed them and the pistons did not retract. I rode the bike with my emergency lights on and did not touch the brakes the rest of the way until I got to my parking spot at my apartment. Sure enough when I pulled the brakes the same thing occured, the bike stopped violently and gave a clunk sound. I have a short clip of the ride home to better explain what happened. The action is in the last couple seconds or so.



    Any input or suggestions would be greatly appreciated. I love this bike, but I'm a little scared of it now.
     
  2. Terry Smith

    Terry Smith Member

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    I'm going to sound like a grumpy old man here but there is nothing mysterious about the linked brake system. The front lever works the front caliper pistons. The back brake works the back caliper outer pistons and the front centre right piston. If you are moving, using the front brake causes the left caliper to rotate which engages the centre piston in the back brake via the secondary master cylinder on the left fork. That's really about it, there is the proportioning valve and delay valve but they are separate to that. How about providing some basic diagnostic info: which wheel is now dragging??? My guess is it is the back brake centre piston as the root cause of your graunchy brakes, which means the SMC is not allowing brake fluid pressure to release. If you crack the rear centre nipple to release pressure and the brake now releases, that means a clog in the tiny compensating ports in the SMC, or a seized SMC piston that can't move after actuation. This is all about cleanliness and flushing out old brake fluid in a timely manner. The linked brakes are unforgiving of bad maintenance, but like all Honda products they are well-designed and if looked after will work very reliably. The other things to check (like all hydraulic brakes) are that the pistons move reasonably freely AND the caliper slide pins move freely to allow the caliper to move side-to-side.

    26,000miles in 15 years is very low usage; 2000 miles/year!! What other deferreed maintenance is waiting to bite you in the butt?
     
    Last edited: Dec 4, 2019
  3. fink

    fink Member

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    Did Honda dealer do any work on bike? Or has the work still to be done? If it has been done, then take it back to the shop and get it checked (better still get them to collect it).
    I think its fantastic that in USA you can get warrantied stuff done 15 years later.

    Have or did you check the discs and see if they were heating up?
    Did you do the work with the aid of a manual or some other form of instruction?
     
  4. Diving Pete

    Diving Pete Insider

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    I think they have put the 'pin' in the wrong way around.
    This stops the fluid transfer for the linked brakes - Its on the left front caliper. Will try & find note about it. 20 minute fix - REALLY EASY..
     

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