VF500 Interceptor -- No front brake pressure

Discussion in '1st & 2nd Generation 1983-1989' started by straycat, Feb 23, 2019.

  1. straycat

    straycat New Member

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    Need some input here guys --- I noticed that the lever on my 85 VF500F was super spongy and basically goes to the bar, only minimal pressure.

    I bled the brakes 4x , fluid is clean and clear, no bubbles-- no improvement

    Bled the master cylinder and Tied the lever back for 12 hours -- no improvement

    Changed the Master Cyl for one that was on a VF1000R (worked when removed), re bled everything -- no improvement

    Calliper pistons move freely and the calliper moves when the lever is pulled, there is pressure on the rotor but not sufficient.

    If I leave it for an hour or two, when I go back there is absolutely zero pressure at the lever, straight to the bar, and after a few pumps I get some pressure back but not much.

    No fluid leaks evident.

    Next is a Calliper swap, unless anyone thinks I have 2 shagged master cycl's on my hands.

    My bet was Master Cyl, but im certain the one I used was working when it came off the VF1000R. not to say it couldn't be f'd now.

    Thoughts?
     
  2. Captain 80s

    Captain 80s Member

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    Take some heavy pliers and pinch the rubber line right out of the master cylinder. If it is a firm lever, problem is down stream and possible one (or more) of the hoses has failed. If it is still spongy, unlikely but not impossible, 2 funky master cylinders.
     
  3. squirrelman

    squirrelman Member

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    Crush washers may be bad. the more you bleed the mc, the crusheder they get.
     
  4. straycat

    straycat New Member

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    Will try the pliers tomorrow, I have new crush washers on.'

    thanks for the ideas.

    I also noticed some fluid on one calliper tonight, ive cleaned it up and will see if the blue shop towel I wrapped it in has fluid stains tomorrow morning,,,maybe there is a leak.
     
  5. straycat

    straycat New Member

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    used the plier pinch to test the master cylinder --- Master is good!

    I pinched the hose right above the right calliper and the problem went away -- culprit is the right calliper !

    thanks for that simple tip !
     
    Terry Smith likes this.
  6. straycat

    straycat New Member

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    Well, still no luck. Ive changed EVERYTHING now, master cylinder, both callipers and all the brake lines, 3 full containers of fluid and the lever still goes to the bar. Not the first set of brakes Ive bled in my life thats for sure, ive done tonnes of them, I am now officially out of ideas.

    if I pinch either line just by the callipers the lever firms up incrementally, no matter which side I pinch, I suspect that means air still in there but only clean clear fluid is coming out. no bubbles. ive tapped the callipers, ive moved the bike around in attempts to dislodge any air.

    im lost

    I've parked the bike out of frustration, (2 days lost on this), it was either that or roll it off the ramp into 6 ft of snow, never to be seen till spring when I'd haul it to the land fill site.

    Damn thing.
     
  7. Captain 80s

    Captain 80s Member

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    Crack each banjo bolt and do a "bleed" there. It's messy so wrap real good with rags. And maybe take off the upper cowl and fender. I've found that's where air gets trapped often.
     
  8. straycat

    straycat New Member

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    ok, I did the upper banjo yesterday, will try the others.

    I may try a syringe and reverse bleed it too

    thanks!
     
  9. VF1000Fe

    VF1000Fe New Member

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    With the Brake Lever fully relax'd, the lines are open,,.. any Air Bubbles would eventually float all the way up into the Reservoir, or Top of the Brake Caliper.
    I've lean'd the bike over one way for the night, then lean'd the odder way for another night.
    Air can get stuck at the Brake Line Splitter, at the Lower Fork Clamp.

    If no Brake Oil is leaking, and the Air is out, then it must be a Master Cylinder Plunger leak (Tear in Rubber Piston?, Scratch in Cylinder?).

    I feel for ya,,. been there,,..
     
  10. jeremyr62

    jeremyr62 New Member

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    Try tapping the brake lines as you pulse the lever. You can get air bubbles sticking to the tube walls and you have to dislodge them. We have all been there. If the lever is is soft and you don't have a fluid leak and the MC is OK then you must have air in there somewhere. You can also try taking the calipers off and pushing the pistons right back into the calipers to lower the volume of fluid and push any air back towards the MC.
     
  11. straycat

    straycat New Member

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    Thanks, yep done all that. tapped the lines, tapped the callipers, when I changed the callipers I had the pistons all the way in.

    I just ordered a mityvac, ill try that too along with reverse bleeding.

    I do agree, there is air in there
     
  12. jeremyr62

    jeremyr62 New Member

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    I found that rapid small displacement pulsing of the lever and watching the vent in the open MC was a good clue to trapped air. Sometimes it would take a while to dislodge the air bubbles but it would eventually work and you would see them emerge into the fluid.
     
  13. Captain 80s

    Captain 80s Member

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    Can't tell you how many times I've been standing there slapping at the tip of the brake lever forever watching the air bubbles pop up out of the tiny hole under the "protector". It is a good time to enjoy a beer or two. And then finally a HUGE one comes out and it feels better.
     
  14. straycat

    straycat New Member

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    are we still talking about brake bleeding here ?

    left the lever tied back overnight and it was alot better, im away for work for a few days so ill check on it when i get back. I ordered a new brake bleerd mityvac as well. if it persists ill also try the reverse bleed.
     
  15. Captain 80s

    Captain 80s Member

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    Kinda... it's that little hole under the little metal cap at the bottom of the master. If you repeatedly rap on the lever (not taking it to the bar) you can get air bubbles to escape through that hole. I've used that method after rebuilding brake systems when not quite getting a good bleed. But like I said, I've stood there for a while slapping that lever end watching tiny bubbles come up and then finally a big one.
     
  16. Diving Pete

    Diving Pete Member

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    I had the same issue on my nc24. I'd put the master cylinder together incorrectly.
    Don't over think this.
    Start at the master cylinder.
    Take the lines off the master.
    Put finger over the end of the master cylinder to block the hole and pull the lever - is there pressure or are you still hitting the bar
     
  17. Captain 80s

    Captain 80s Member

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    Don't think he had rebuilt anything and he pinched the line right after the m/c and it was solid.
     
  18. NorcalBoy

    NorcalBoy Member

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    if it was the stock line....prolly blew a hole in it. The last thing I would be doing to a 30 year old brake line is crushing it with pliers.
     
  19. squirrelman

    squirrelman Member

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    Try removing the MC from the bar and hold it vertical with the lever at the high point while tapping MC and lines.
     
  20. Captain 80s

    Captain 80s Member

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    Good point. The stock lines at this point are suspect in the first place.
     
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