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Thread: Tuono Brake problem? Need assistance.

  1. #1
    apriliaforum Member
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    Tuono Brake problem? Need assistance.

    OK here is the deal. Pushing bike around, spinning wheel on fork stand when cold, front wheel brakes seem completely normal. Ride the bike for a very short period of time, using the brakes, and the brake lever goes rock hard and the calipers will lock up on the rotors. Thus, put it on a fork stand and the wheel will not move.

    Things done, with 'thousands' of suggestions from mechanics, riders, and racers. This bike has seen the ditch on it's side, not by me, so many items checked with that in mind. Bike only has 600 miles on it.

    1. Rotors not bent nor warped.

    2. Calipers completely cleaned and pistons seem to move and retract normally. Brake pads are stock, not warped and moving normally on pins.

    3. Forks not bent, caliper mountings not bent.

    4. Fluid has been changed, rechanged, different types with mucho bleeding and rebleeding. Dot 4 fluid will take longer to lock up than the Dot 5.

    5. Master cylinder shows no damage. Fluid cup works normally and fluid will drop normally with any brake bleeding done. Have also cleaned all the above when performing inspection.

    Could the Master Cylinder be screwed up and causing this? One of last suggestions I got from a well regarded racer/mechanic is to find a different one and put on to see if this remedies the problem.

    OR

    The only thing that came to mind at the end of this process is the brake lever. I, not having another Mille or Tuono to compare because of no local dealer or other bikes, am pretty sure the lever has been replaced after the accident by previous owner(s). It outwardly appears to work normal and fit normally. But, I noticed on the AF1 shopping items that in the description of the lower cost replacement brake lever that it says something along the lines of "true replacement lever, fits correctly unlike replacement lever from LP".

    It appears that the lever that is on this bike slightly pushes in the cylinder when lining up the holes for the lever bolt to fit in. Wondering if it might be just ever so slightly applying brake pressure, causing rapid heat buildup and ever increasing pressure? I'm just not a brake expert (or anything else for that matter), and I do not have another brembo master cylinder/brake lever to compare at this time. I'm wondering what the "incorrect fitting" of the LP lever does or amounts to? I'll definately call AF1 tommorrow unless Ed or someone else replies here with an answer before I have an opportunity to do so.

    This certainly has many heads being scratched that have more moto mech experience than me. I'm betting (HOPING) that someone here has a "you stupid idiots" answer for me!

    Thanks in advance. BTW, I'm going into the hospital tomorrow for an outpatient procedure so will not be able to acknowledge any replies until later in the day. So please do not think I'm disregarding your suggestions.
    Knee down, is a corner taken!

  2. #2
    apriliaforum prov-nov
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    I think you've hit on it with the brake lever. And it's not that it's applying a bit of brake pressure, but more likely that it's causing the bleed-back hole in the master cylinder to be closed. This is a tiny hole that allows expanding brake fluid back up through the system so that it won't lock the brake.

    Try another lever or grind the nubbin so that it doesn't apply any pressure; the master cylinder plunger should extend fully and freely.

    Good luck.

  3. #3
    apriliaforum Member
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    I was wondering about a "bleed back hole". No one, in this case, has mentioned such a thing being blocked, but you've pointed out my uneducated suspicion.

    thanks Mazza.
    Knee down, is a corner taken!

  4. #4
    apriliaforum prov-nov flip's Avatar
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    Mazza is right there needs to be a little free play other wise it jacks up the pressure like a car jack thus holding on the brake until it is released. I had this problem with my Scorpa.

  5. #5
    apriliaforum Member
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    Sounds to me like air in the system.
    Don
    Red 2003 Aprilia Tuono

  6. #6
    apriliaforum Member
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    Tuono Tex; It would be completely surprising for it to be air in the system since I'm on the third type of Brake Fluid with complete flushes inbetween. And just to make sure, the last type added I used just short of a whole bottle of fluid bleeding the system at all three bleed screws.

    I'm going to check further into the brake lever now that I'm back home.

    Thanks guys.
    Knee down, is a corner taken!

  7. #7
    apriliaforum Member
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    I talked to Micah at AF1 and it probably is an LP lever. Therefore causing the problem. He's getting a new one on the way to me.

    You guys down there are lucky to have them in your back yard. I'm lucky they put themselves on the net.

    Thank You AF1 guys!
    Knee down, is a corner taken!

  8. #8
    apriliaforum newb
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    Dodgy brake leavers

    Had the same problem with mine when I replaced the leaver with an aftermarket one. Ended up filing some of the excess material away so that It wasn't applying brake when you fitted the lever. Drove me nuts for a while too. Not to mention the constant endo's :-)

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