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Thread: Recurring Clutch and Rear Brake Issues

  1. #16
    apriliaforum expert kzmille's Avatar
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    Some drag is normal but there have been instances where overfilling the reservoir caused a problem as well as replacement levers that did not provide enough free-play which prevented fluid returning to the reservoir.

  2. #17
    apriliaforum expert SoulDaddy's Avatar
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    I understand a bit of drag is normal (even though a Triumph Sprint I'm currently babysitting has virtually none), but I can barely get a half to three quarters of a revolution of the wheel with a good, solid spin. Seems much too tight.

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  3. #18
    apriliaforum expert kzmille's Avatar
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    Sometimes you can improve this by pushing all the caliper pistons fully into the caliper and then pumping them back. You may have to pull the calipers to accomplish this. If you do remove them torque all the mounting bolts before finally pumping the pistons and pads back to the disc.

  4. #19
    apriliaforum expert chad951's Avatar
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    One more thanks to kzmille for this thread...



    I tried this technique to bleed my rear brake on my 04 Factory this weekend and it worked perfectly. For the first time since I purchased my bike new I have a rock solid rear brake. The pads still need to seat with the rotor but it will stop the bike very well on its own.

    If any of you doubt this technique please don't. If you do not have a rear brake and would like one please find a competent assistant and follow the instructions in kzmille's post for bleeding the rear brake. If you follow the directions to a "T" you will have a working rear brake in no time.

    Thanks again kzmille!
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  5. #20
    apriliaforum Member mike p's Avatar
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    Clutch issues

    Quote Originally Posted by kzmille
    This issue of clutch hydraulic problems just won't go away. The front and rear brakes have also caused problems for many. Most, if not all, of these problems are caused by improper bleeding. Motorcycle hydraulic systems (brake and clutch) are notoriously difficult to bleed. On the clutch and front brake it is because of the vertical layout and the small volume of fluid displaced by the master cylinder. On the rear brake the volume displaced is even less and the caliper is usually generic, meaning not specifically designed for the aplication. This results in the bleeder being in the wrong position necessitating caliper removal and repositioning before effective bleeding can be achieved.
    Using the old back yard method of pump and bleed, it is virtually impossible to properly bleed a motorcycle clutch or front brake. Vacuum systems like the Mityvac are a step in the right direction but are limited. The most effective way to bleed is with forced fluid injection.
    Phoenix Systems is a company dedicated to providing tools and knowledge to the automotive indusrty for bleeding brake and other complicated hydraulic systems. They offer a variety of fluid injection tools that work better than any other manual system I have seen. They also offer technical knowledge which covers just about every difficulty you might encounter while bleeding complicated hydraulic systems. Please check their web site at http://www.phxsyss.com/. All that being said, I have been using these same methods for over twenty years but with tools that are far less expensive. With a simple plastic medical syringe, of from 10 to 75 ML, you can use reverse fluid injection to effectively bleed any motorcycle brake or clutch in very little time.
    Lets assume the system is clean and the slave cylinder is free of contamination; you do not want to force contaminated fluid from your calipers or clutch slave up into the master cylinder. Suck all the fluid out of the reservoir and wipe it clean. Take your clean syringe and fill it with new brake fluid. Attach it with a clear vinyl tube to the bleeder at the caliper or clutch slave. Open the bleeder and inject the fluid while watching the level in the reservoir. Stop when full. Close the bleeder. Suck out the reservoir and repeat as needed. This is basically all there is to it.
    There are some things that you have to watch for. On rear brakes you still have to remove the caliper but instead of positioning it with the bleeder up, you must hold it with the brake hose port up.
    One last thing about bleeding our Mille clutches. Something that is being overlooked is that there is not actually a bleeder on the slave cylinder itself. It is part of the banjo bolt.
    Automotive clutch slave cylinders have the bleeder located at the top of the slave so that when bled the fluid is flushed through the cylinder. This does not happen with our system so it is possible to bleed and still have a pocket of air within the slave cylinder. It is however easy to remove it.
    After bleeding as above and filling the reservoir, remove the three screws securing the slave cylinder. Remove the cylinder and hold it in its normal attitude then tip it slightly to the right (as if you were leaning the bike to the right). Be sure the reservoir cap is on. Then allow the internal spring to slowly push the piston out 5 or 6 millimeters and push it back in forcefully. Repeat this several times. Reinstall the cylinder and screws to proper torque. You may want to reverse inject one more time to be sure there are no bubbles in the banjo fittings and hose. THIS WORKS and it takes a lot less time than it did to type this. It is the very procedure described in the aprilia workshop manual.
    There are times, depending on the system layout, when it might be more advantageous to inject fluid into the master cylinder so fluid flows in the normal direction. To do this you must adapt your injection device to the master cylinder reservoir. With any difficult bleeding situation you must be keenly aware of internal passageways, banjo fittings and other possible high spots that might trap air.
    It is also important not to over fill the brake fluid reservoirs. If you try to fill the reservoir all the way it can lead to brake drag. As the calipers warm up the fluid expands and is forced up to the reservoir. If the reservoir is completely full, pressure builds and is transmitted to the caliper pistons causing them to move toward the disc causing drag. As the brake gets hotter it drags more...
    It is also a good idea to crack open the cap and reclose after the bike is fully hot, to vent any pressure. It is important to remember that this same thing can happen with the clutch fluid reservoir and cause the clutch to slip. Leave a little air space!
    Please do not ride your bike if you are not absolutely certain that the brakes are working properly. If you monkey with the actuating rod on front (at the lever) or rear (at the pedal) brake be sure you have detectable free-play. If there is no free-play it can prevent fluid return to the reservoir and cause brake application and lock-up as system temperature rises. If any of this is not clear let me know and I'd be glad to talk you through it.
    Question on the slave cylinder if you were to drain it completely as I want to do. I am going to try the Castrol RSF fluid and would like to know your thoughts on the best way to drain all fluid. Try to suck it out or unsnsrew the three bolts and turn it up side down???. One more thing, about pushing fluid up to the reservoir. If you drain and refill like you mentioned would you run the risk of over flowing the reservoir. Thanks Mike

  6. #21
    apriliaforum expert kzmille's Avatar
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    When I change my clutch fluid I suck the old fluid out of the reservoir and then inject new fluid into the bleeder at the slave till the reservoir is nearly full. Yes, you have to be careful not to overflow the reservoir during these procedures. I repeat this a couple times till the fluid in the reservoir is clean. The only way to be sure that the fluid in the slave gets fully replaced with the new brand is to use the procedure above where you remove the slave and pump the piston in and out and then replacing the fluid and repeating several times till the fluid remains clean during the procedure.

    To really get the slave clean of old fluid and sludge remove it and remove the piston and clean everything, reassemble and bleed. This should not be necessary on a fairly new bike. I have not disassembled the slave on my 5 year old bike yet but probably will the next time I change the fluid next winter.

    I have found that after flushing the slave cylinder this way the clutch fluid remains clean far longer than it used to. Since the last fluid change and careful flushing I have gone 2000-3000 miles and the fluid is still clean.

  7. #22
    apriliaforum Member mike p's Avatar
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    When you push the cylinder in will it take a lot of force, and do you leave the bleed screw open at the banjo joint while doing this ? The fluid is clean since I bleed it about a moth ago so it will be hard to tell if the old or new is coming back out. Does the fluid in the slave remain stagnant during a bleed when you don't remove it, or does it get mixed in with the new ? Thanks again Mike.

  8. #23
    apriliaforum expert kzmille's Avatar
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    Quote Originally Posted by mike p
    When you push the cylinder in will it take a lot of force, and do you leave the bleed screw open at the banjo joint while doing this ? The fluid is clean since I bleed it about a moth ago so it will be hard to tell if the old or new is coming back out. Does the fluid in the slave remain stagnant during a bleed when you don't remove it, or does it get mixed in with the new ? Thanks again Mike.
    It does not take a lot of force to push the piston in. You just squeeze it between your thumb and fingers. With the bleeder at the slave open you just force the fluid out the bleeder. With it closed you force the fluid and air up to the MC, in effect reverse bleeding. This is the whole point of doing it with the bleeder closed. Air bubbles do not like to go down hill. Forcing the fluid from the slave up to the MC flushes the bubbles up to the reservoir. Since the bleeder is on the banjo fitting and not on the slave cylinder itself the fluid in the slave is somewhat stagnant and does not get flushed and/or replenished with normal bleeding. By repeating the pumping procedure on the slave you can replenish the old fluid in the slave cylinder.

  9. #24
    apriliaforum Member mike p's Avatar
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    Quote Originally Posted by kzmille
    It does not take a lot of force to push the piston in. You just squeeze it between your thumb and fingers. With the bleeder at the slave open you just force the fluid out the bleeder. With it closed you force the fluid and air up to the MC, in effect reverse bleeding. This is the whole point of doing it with the bleeder closed. Air bubbles do not like to go down hill. Forcing the fluid from the slave up to the MC flushes the bubbles up to the reservoir. Since the bleeder is on the banjo fitting and not on the slave cylinder itself the fluid in the slave is somewhat stagnant and does not get flushed and/or replenished with normal bleeding. By repeating the pumping procedure on the slave you can replenish the old fluid in the slave cylinder.
    I will give it a try and watch the reservoir closely for over flow. Do you have a estimation on fluid content with a complete drain.

    Thanks

    Mike

  10. #25
    apriliaforum expert kzmille's Avatar
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    Quote Originally Posted by mike p
    ...Do you have a estimation on fluid content with a complete drain...
    No, but it is not much. A pint should be plenty. I always buy it by the quart having so many vehicles to take care of. Though I'm pretty sure I mentioned it in the article above, something often overlooked is making sure that the hose from slave to MC does not have any high spots where air tends to stop.
    Last edited by kzmille; 05-03-2006 at 08:25 PM.

  11. #26
    apriliaforum Member mike p's Avatar
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    Quote Originally Posted by kzmille
    No, but it is not much. A pint should be plenty. I always buy it by the quart having so many vehicles to take care of. Though I'm pretty sure I mentioned it in the article above, something often overlooked is making sure that the hose from slave to MC does not have any high spots where air tends to stop.
    If I were to suck the fluid out of the front brake calipers wouldn't you need some kind of small hose to fit inside the bleeder to reach the fluid or do you remove the calipers and turn them over to suck out the remaining fluid. One more question, in my owners manual it says to replace the caliper bolts when you reassemble this seems a bit odd to me any comments on that issue.

  12. #27
    apriliaforum expert kzmille's Avatar
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    Quote Originally Posted by mike p
    If I were to suck the fluid out of the front brake calipers wouldn't you need some kind of small hose to fit inside the bleeder to reach the fluid or do you remove the calipers and turn them over to suck out the remaining fluid.
    I'm not sure what your getting at there Mike. I recommend injecting fluid into the caliper bleeder with the caliper in place.

    Quote Originally Posted by mike p
    One more question, in my owners manual it says to replace the caliper bolts when you reassemble this seems a bit odd to me any comments on that issue.
    I think that is a bit overkill. I have never replaced mine and they have been torqued dozens of times. Good place to use a torque wrench.

  13. #28
    apriliaforum Member mike p's Avatar
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    Quote Originally Posted by kzmille
    I'm not sure what your getting at there Mike. I recommend injecting fluid into the caliper bleeder with the caliper in place.


    I think that is a bit overkill. I have never replaced mine and they have been torqued dozens of times. Good place to use a torque wrench.
    IF you inject fluid into the bleeder the old fluid in the front brake capiler would still be there correct.I was talking about a complete drain just like we discussed on the clutch slave. I guess I believe that if you put a mity-vac or what ever type of devise you have to remove fluid on the bleeder it will not be able to pull the fluid from the bottom of the caliper up to the top of the bleeder. Is the suction that strong that the fluid will flow up with out any physical contact. Thanks again for your replys.

  14. #29
    apriliaforum expert kzmille's Avatar
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    Quote Originally Posted by mike p
    IF you inject fluid into the bleeder the old fluid in the front brake capiler would still be there correct.I was talking about a complete drain just like we discussed on the clutch slave. I guess I believe that if you put a mity-vac or what ever type of devise you have to remove fluid on the bleeder it will not be able to pull the fluid from the bottom of the caliper up to the top of the bleeder. Is the suction that strong that the fluid will flow up with out any physical contact. Thanks again for your replys.
    Ok, I understand what you are getting at. Regardless of which method you employ to bleed, there will be fluid in the calipers that will not get renewed. A better way to ensure fresh fluid throughout is; after removing all the old fluid from the reservoir, push all eight caliper pistons fully into the calipers. This will displace all of the fluid. Flush and bleed, then pump the pistons back out. If you repeat this a few times you will then be assured that you have fresh fluid throughout the calipers. Most will not go to this trouble but this will circulate new fluid around the pistons and somewhat clean the caliper. This moving the pistons back and forth can actually improve the free movement of the pistons by restoring some lubrication to the seals. In the brake shop we called it exercising the calipers. Just don't pump them out too far. If one does pop out it's no problem. Clean it and the seal and bore, lubricate the piston and seal with brake fluid and push it back in. Inevitably there is one or more pistons that don't want to move until the other pistons have stopped against the disc or other stop that you insert between the two sides of the caliper. While the pistons are extended wipe the exposed portion with a clean cotton cloth. Do not put any petroleum lubricant on the pistons.

    The next step to really ensure a clean caliper would be complete disassembly and cleaning.
    Last edited by kzmille; 05-06-2006 at 05:54 PM.

  15. #30
    apriliaforum Member mike p's Avatar
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    Quote Originally Posted by kzmille
    Ok, I understand what you are getting at. Regardless of which method you employ to bleed, there will be fluid in the calipers that will not get renewed. A better way to ensure fresh fluid throughout is; after removing all the old fluid from the reservoir, push all eight caliper pistons fully into the calipers. This will displace all of the fluid. Flush and bleed, then pump the pistons back out. If you repeat this a few times you will then be assured that you have fresh fluid throughout the calipers. Most will not go to this trouble but this will circulate new fluid around the pistons and somewhat clean the caliper. This moving the pistons back and forth can actually improve the free movement of the pistons by restoring some lubrication to the seals. In the brake shop we called it exercising the calipers. Just don't pump them out too far. If one does pop out it's no problem. Clean it and the seal and bore, lubricate the piston and seal with brake fluid and push it back in. Inevitably there is one or more pistons that don't want to move until the other pistons have stopped against the disc or other stop that you insert between the two sides of the caliper. While the pistons are extended wipe the exposed portion with a clean cotton cloth. Do not put any petroleum lubricant on the pistons.

    The next step to really ensure a clean caliper would be complete disassembly and cleaning.
    Ok, thanks for your detailed replys. One more inquiry. I was thinking about replacing both the reservoirs with billet items but can not seem to find any manufacturer other than Hooligan. I don't think there application is a direct fit. Do you know of anyone who makes something that looks good and will work properly?

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