clutch bleeding

Discussion in 'Mechanics Garage' started by reg71, Aug 16, 2006.

  1. reg71

    reg71 Poser Staff Member

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    Hey guys, I'm having trouble bleeding the clutch. Here's the deal, I fill up the master cylinder and put the lid on, squeeze the handle a few times then hold it. Then I give the bleeder a half crank, watch the air bubbles and tighten it back down. Repeat until no bubbles. The pressure never seems to build... When I hold the clutch in, no disengagment... What's next? I have also noted that my master cylinder empties quickly, but I can't find any leaks... How much brake fluid should it take for a system that was totally dry? How long does it typically take? I have run pretty much whole small container through it except what I poured in a jar to keep the bleeder hose submerged. I'll stick some pics on this so you guys can look and see if there is anything obviously wrong here...
     

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  2. jchag1718

    jchag1718 New Member

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    Hey Reg... I looked at your setup in the picture and I have some suggestions. Use a clear piece of tubing so you can see the bubbles as they exit. Next you need to raise the jar of fluid higher than the level of the bleed valve. You can leave the cap off the mstr cyl and just keep adding fluid until no more bubbles come out when you squeeze the lever. Top off the mstr cyl, replace the cover and you should be good to go. If it still won't disengage the clutch after this and you can't see any leaks, then you will have to remove the slave cyl to see if its moving when you pull in the lever. It could be stuck. Let me know how it turns out.
     
  3. reg71

    reg71 Poser Staff Member

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    thanks a lot... I'll keep you posted. this was driving me crazy... I hope that works.
     
  4. reg71

    reg71 Poser Staff Member

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    Ok, did like you said. Everything seemed okay, the bbubles bled out, etc. But, the clutch never seemed to build any pressure. I talked to my dad about it and he said it was probably the master cylinder being bad or the slave cylinder. He said to take off the slave cylinder and pull the clutch and see if I could see any movement or feel any pressure. (keep in mind he has never seen a VF so he's trying to give me suggestions just based on phone conversation. Any other suggestions for diagnosing my prob? I'm getting close to taking it to a dealer, but I hate to do that if it's something I can fix...
     
  5. M-Crew

    M-Crew New Member

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    If its not building presure and there is no leak in the slave cylinder.I could almost be certain that its the master cylinder not the slave.Save yourself some money and see if you can repack/seal that master first.:smile:
     
  6. jethro911

    jethro911 New Member

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    Reg,

    Try building up some pressure by pumping the lever and then crack the banjo bolt at the master cylinder. It should ooze out some air at that point. If there are any other banjo bolts, do the same thing. Air seems to get trapped at these spots.

    If you still have no luck, pull off the banjo bolt at the master cylinder, fill it with fluid, hold your finger over the output hole and pump the lever. If you do not feel pressure, there is a problem with the seals in the master cylinder.
     
  7. reg71

    reg71 Poser Staff Member

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    okay. thanks. I'll keep you posted. :)
     
  8. jev.

    jev. over there

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    Ditto. Most of the time I have to bleed the banjo bolts to get all the air out.
     
  9. vifferj

    vifferj New Member

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    I've had this problem numerous times. The only way i've cured it was to take the slave cylinder off the bike and stop the piston moving by clamping with a G clamp or similar. Remove the master cylinder banjo bolt and bleed reconnect the hose and bleed at the cylinder end , finally bleed the cylinder at the bleed nipple . Remove g clamp and reinstall.
     
  10. WhiteKnight

    WhiteKnight Well-Known Member

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    Any luck yet reg? This isn't really clutch related, but I had an 84 CR 125 wuth a front disk brake. I always felt it was "spongy" feeling. The night before a race I decided to bleed the brake (note: never do soemthing like this the nigth before). Well, I lost all pressure. I kept bleeding for about an hour or so before I gave up. I got up early the next morning and started bleeding the brake again. After about an hour I got pressure again. I must have had a stubborn bubble and it finally passed thru the line. Keep at it as it may eventually come back. Just my $.02. I bled my clutch about a month ago with no problems at all. I also did the front brake as it had a sticking point in it and it now is much smoother. I know you did this, but make sure you use the proper DOT fluid. If it says use DOT 3, you can probably use 4 and it will be ok as I have done that before on my CR.

    You can also get a mighty vac bleeder. Its a vacuum bleeder system, usually available at any auto parts store. It has a neoprene (clear) line that connects to the bleeder valve. Hook it up, pump up vacuum in the line and crack the valve. Close valve when bubble no longer appear. I have one somewhere, I am just to lazy to look for it or I would have used it on my bike. lol
     
  11. reg71

    reg71 Poser Staff Member

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    haven't tried again yet. been working all week. very busy last couple of days. people trying to die and all that. only lost one so far this week and considering the batch we had, that's saying something... the clutch is on my to-do list, though. Man I hope that guy finishes my fork seals soon. I haven't gone this long without riding since I got my bike.

     
  12. CharlieT

    CharlieT New Member

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    Just went thru this with my old '84 VF700. Even with the tube on the bleeder going up to a small bottle above the slave and no air bubbles, could not get any pressure to build up. Finally took a 30cc syringe and attached that to the hose I had hooked on the bleeder valve. Kept filling the master cylinder and pulled the fluid thru until it came out with no air bubbles and ice clear fluid. As I started pulling the fluid thru, much of it at first was very milky.....water in the fluid! Once I got clear fluid, it's been working fine.
     
  13. jchag1718

    jchag1718 New Member

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    This has been a great thread. :first: Thanks for starting it Reg. Alot of good info here. If someone can't solve their hydraulics problem here, something must really be broken. To all who contributed, keep up the good work. Later.
     
  14. reg71

    reg71 Poser Staff Member

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    ok, I did this and it built up pressure instantly. I reattached it and then undid the banjo at the slave and held pressure on the line, it built pressure instantly. I pulled the slave off and put my finger over the hole in the middle, when I pressed the clutch, fluid came around the outside edge. Is this normal or not? I'm not really clear on the mechanism between the slave cylinder and the rod that goes through the case(is it a clutch rod?) Next step?
     
  15. CharlieT

    CharlieT New Member

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    If fluid came out around the outside edge of the piston in the slave cylinder, you just found your problem!!! SHouldn't be any leakage there...can't build pressure and push the piston out with a leak in the system. Just go ahead and rebuild the slave cylinder.

    BTW, the hole in the middle of the piston is wear the clutch acuating rod (?) sits. RUns thru the engine, thru the center of the clutch on theb other side of the engine. Piston pushes the rod which in turn pushes oout the clutch plate, compressing the springs and releasing the pressure on the discs/floaters.
     
  16. jethro911

    jethro911 New Member

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    Sounds like you have made some progress Reg!

    The slave cylinder has a piston in the middle that pushes against the rod and the rod (which passes through the engine to the clutch on the opposite side) actuates against the clutch release bearing.

    The center of the slave, where you placed your finger moved far enough to allow the piston to come out past the seal and leak.

    If the piston did not move and leaked, the slave needs new seals. If this is the case it should have been leaking before so I doubt it.
     
  17. mello dude

    mello dude Member

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    Reg - alot of good stuff here, I think Jethro may be on to it - work on the seals to the slave. Looks like you have traced it to there. I cant add much to what has already been said.

    2 recommendations to get down to bleeding - get a Mityvac pump and bleed container - it will help you get going for the initial bleed.

    Then I like to replace the stock bleed valves with the check valve type. With these you crack them loose with your bleed hose attached and when you pump the M/C you dont have to close the valve to keep pressure. Pump till the bubbles are gone, close the valve, and your done. Spiegler Performance is a source for these.

    A few other tips -
    -I like to use a little spring hose clamp (buy at any auto parts store) to keep the bleed hose from falling off the bleed valve. It saves some agravation.

    - When you rebuild your slave and the system will be "dry" again. Sometimes if you fool with a dry M/C and pull the lever all the way back before refilling the piston seal will ketch an edge of the port of the fluid path and flip the seal backward. (SOB!) After that no matter how many pumps - you wont get pressure. You got fluid on both sides of the piston! The only fix after that is to drain it and disassemble and flip the seal back in the correct direction. - To avoid, pull the lever back only about half way till you get going with some pressure first. - Lesson learned - dont pull lever back to the handlebar on a dry M/C.

    Last suggestion - on fluid use Valveline Syn Power - Its a synthetic and it exceeds Dot 3 and Dot 4. It works close to a Dot 5 without the drawbacks. I have used it for years in my cars and bikes and have had good results. (Avoid Dot 3 fluid!)

    Best of luck,
    MD

    --Thinking about it again it wouldnt hurt to get a M/C rebuild kit anyway, If yours is original on that old bike, it's due to wear out anyway. Hey CharlieT - do you agree?
     
    Last edited: Aug 24, 2006
  18. reg71

    reg71 Poser Staff Member

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    well it could have been leaking insidethe case, I don't know. The fluid was going somewhere I guess. Ok, next question, I looked on bike bandit trying to find a slave cylinder rebuild kit or seals or something but no luck. I'm gonna try my local dealer tomorrow, but if no luck, where online to go and what do I ask for? When I look at the inside the slave I don't really see how to take it apart. I think I'm gonna try to do pics with this one so in the future someone else has something to look at.
     
  19. CharlieT

    CharlieT New Member

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    Yeah, I agree..just rebuild them both at the same time. For one, they are the same age and if one is showing leakage/sings of wear, the other might not be far behind it. The other thing that can happen.... you got a leaking slave, so you can only build up "X" amount of pressure in the system befoer it starts to leak. So you rebuild the slave, and now it can hold pressure up to "XXXX" pressure. So now withe the increased pressure your slave can now hold and allow to build up in the system, you just overcame the "XX" level of pressure your old master cylinder could hold without leaking. Wasn't a noticable issue before because it was the slave that leaked first and limited the pressure, but with your new slave able to hold much more pressure, you just sprung a leak in the master cyllinder. SO, yeah if your doing one, better off to go ahead and do both.
     
  20. CharlieT

    CharlieT New Member

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