Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Featured Hydraulic Clutch Issue

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by icemaker, May 10, 2015.

  1. I noticed recently the clutch grab point on my Gen 5 VFR 800 getting further out to the point where it was difficult to take off.
    I changed the fluid, which was quite bad, but it didn't fix the issue and on a recent tour the clutch started slipping while riding.
    So I figured I would need to change the seals in the master cylinder and slave, and for good measure, I also bought new clutch plates and springs.
    So stripped, cleaned and installed new seals in the master and slave cylinder but it didn't solve the problem.
    Next, changed out the clutch plates, which looked fine but swapped them out anyway. Replaced the springs and there was quite a difference in length between the old and new so I thought that had to be it. Put everything back together and went for a ride.

    Initially its was ok, not as good as I expected but after 20 or so minutes it started slipping worse than before I did all the work. When I accelerated to 5k rpm it would then just rev out as if I had the clutch in.
    Super pissed off and its now doing my head in.

    I reckon its something to do with the the master or slave cylinders. It nearly took me a full 500ml bottle of fluid to get the air bubbles out and even then I had to pump the lever a couple of times for it to come up solid.

    Any ideas, tips, tricks, anything that points me in a direction, would be hugely appreciated.
  2. sounds like it's "pumping up".
    the "further and further out" thing is because too much fluid between master and slave, and each application adds more fluid, pushing clutch further and further in

    either slave is sticky and not coming back all the way (= slightly extra volume that gets filled next stroke)
    or master is not bleeding off when lever is released.

    if it was former, not so likely that slave is stickier than clutch spring force, so..
    more likely latter? bleed port blocked, or master piston not coming back far enough?
  3. That makes complete sense.
    I can see the master piston operating smoothly, seems normal I suppose but not sure if it going through the full motion.
    The bleed port on the slave is not in the best nick but I did blow air through it, cleaned it and used teflon tape to provide a better seal.
    Im leaning toward slave cylinder problem. Thoughts on possible cure? Seals and piston spring are brand new.
  4. hard for slave to have things go wrong if everything is in order.
    it's just hydraulic pressure + piston spring pressure VS clutch spring pressure.
    if seals are in correct orientation, and bore has no damage.. hard to see how it wouldn't work properly.

    the clutch spring pressure is a lot higher than the piston spring pressure, so for the slave to remain sticking too far out (and to get further out with time), needs extra hydraulic pressure in the line..

    I think it is most likely due to the master cylinder..
    if there is check valve at the end, maybe it's holding too much pressure and not releasing line pressure?
    then when new fluid gets pulled from res into the chamber, it adds to line volume.

    brake master schematic for reference http://www.3cyl.com/mraxl/manuals/maint/6-54.jpg
  5. Your a legend Stu, Ill pull it apart this week and sus it out. Thanks mate
  6.  Top
  7. Yeah cool, Ill work out a day and let you know. Been doing OT a couple of days a week at work so Ill see where Im at in the next couple of days. Might be a weekend job, Ill keep you posted.
  8. that reminds me.. you have aftermarket levers?

    if you have the originals still, be good to eyeball the dimensions.
    you could also whack the original lever back on, and see if problem goes away :)

    from another forum
    "After market levers? I fought with this for a while before I realized that what I thought was freeplay was actually just the system building up enough pressure to work. In fact I had no freeplay, the plunger on the master cylinder was out too far which prevented the return port in the m/c from opening when I released the lever. This caused a pressure buildup as the bike came up to temp and gave me the exact same symptoms you are describing."

    and another
    "Next up - ensure that the free play on the lever adjustment is to spec. There's an adjustment that takes up the 'slack' before the lever actually pushes on the piston of the master. Too much slack and you don't get enough movement in the slave. But there is a TOO MUCH position - having no free-play in the lever can block the fluid return port. YOu'll end up pumping up the slave and it won't return leaving your clutch stuck in a disengaged position."

    (and stupid me was looking for Kawasaki master diagrams LOL)
  9. Stock levers are on but I know exactly what your talking about. It happened on my Z1000 when I put the new levers on. Locked up the brakes after a couple of laps around the carpark at work. Lucky I didnt hit the streets!!
    • Like Like x 1
  10. #10 oldcorollas, May 10, 2015
    Last edited: May 10, 2015
    I was getting confused between your bikes :D

    here suggests the "long rod" at the slave can bind and cause clutch slip?

    master doesn't seem to have valve https://www.motorcyclespareparts.eu...0-2002/f-6-clutch-master-cylinder-544748.aspx

    the rod could not returning could easily explain the symptoms

    and yet another thing it could be :D (the bleed port thing I mentioned before)
    Problem: your clutch slips at speed and the problem gets worse when your motorcycle is warmed up.
    Solution: At the bottom of the clutch master cylinder reservoir you will see a small chrome clip. This is a splatter guard to keep fluid from splattering when you activate your lever with the cover off. Carefully remove it using a toothpick so as not to damage it and you will see what appears to be a partially drilled hole. At the bottom of this is a tiny hole the size of a very small pin which gets clogged very easily especially if the fluid hasn't been changed for a while. This tiny approx. 1/128 inch hole allows just enough fluid to escape back into the reservoir to allow your clutch to fully engage. Your fluid expands when warm and that is why the problem is worse when the bike is hot. This hole is forward of the rubber plunger on the clutch piston so you can unclog it with a small pin without worrying about puncturing the rubber plunger inside. Be careful not to enlarge this hole. After doing this you will find that the clutch not only fully engages but the lever begins to engage almost immediately just like a brand new bike and it is easier to find neutral too.
  11. Do you know how mant friction ans steel plates are supposed to be in the basket? Double check the correct number of both present.
  12. Mate your going above and beyond, Ive got ya on a roll and I really appreciate the effort(y)(y)
    That little hole Ive read about. I blew it out with compressed air and looked clean as a whistle.
    Ill have a look at the rod and see if its moving smoothly

    Hey bud, I bought the complete kit, steel plates, friction and springs. I made sure I installed them in the correct order as I took them out and as per manual. It all should be hunky dory there.
  13. Just started reading this.
    I've had lots of customers bikes where the bleed hole on the brakes (& the clutch) has been blocked.
    This really sounds where your problem will be.
    Disassemble the master cylinder & spray brake cleaner through all holes.
    Also, I wouldn't be using teflon anywhere near brakes/clutches.
    Had a Blackbird where the rear caliper had melted as the fluid couldn't return after application.
    I've kept it to hang on the 'Wall Of Shame'!!
  14. ah,missed the Teflon tape bit.
    bleed nipples use a metal to metal seal (at the base), the thread itself should not be providing any seal, and shouldn't need teflon tape at all
  15. The reason I used teflon tape was to eliminate the bubbles caused by poor sealing of the bleed nipple when using a Mityvac vacuum bleeder. At times I couldn't tell if there was air in the system or if it was sucking air from the threads.
    Had to resort to the old school method a few times but the teflon sorted out that issue. I was very careful not to cover the the bleed hole and just apply it to the treads.

    Cheers for the reply mate. There are only 2 holes in the reservoir and I paid particular attention to make sure they were clean. I did read about theis being an issue and I blew the holes with compressed air. Although I didnt use a cleaner of any kind they did look quite clean before I reassembled.
    As stated above I made sure I only put teflon tape on the threads, could that still cause a blockage in your opinion?
    Because if it is then Ive got a lot of work ahead of me as I also put tape on all the brake nipples of which there are 7 because of the linked brake system on the viffers. And they are a biatch to get to and bleed especially the rear caliper.

    Ive got a sneaking suspicion that it might be the plunger not inserted into the lever properly, similar to the aftermarket lever problem. I hope Im right as its an easy fix.
    Reckon Ill start at the lever/master cylinder and work through the system until its solved.
    Ill keep you guys posted and keep the possible remedies coming.
  16. I usually put the master cylinder through the sonic bath & then spray the cleaner from the reservoir side & look through into the bore to make sure it's clear.
    Use the pressure pack can with an extension tube held against the hole.
  17. #17 ibast, May 11, 2015
    Last edited: May 11, 2015
    It could be mechanical. Check the slave cylinder rod is in good condition and is straight. I may be getting sticky as the bike warms up

    vfr800-clutch-diagram-slave-cylinder-master-cylinder-rod_png. It could be mechanical. Check the slave cylinder rod is in good condition and is straight. I may be getting sticky as the bike warms up
  18. Cheers ibastibast its next on the list after the I check the lever.
    Does anyone know if this rod just slides right out? Or are there any connections that need to be taken care of at the other end?
    Dont wanna pull this out and have bearings or anything else fall out. Might have to consult the manual.
  19. All I've seen slide right out, but check the manual first, as I don't have first hand knowledge of your model.

    The other thought is to check you have the correct fluid. Soemtimes the wrong Dot can damage seals.
  20. These are the references to the lifter rod that are relevant in the manual. Quite vague but seems as though I would probably have to dump the oil again and open take the right hand side casing off. Dont really want to do that unless absolutely necessary.

    PS, Ive got the 99 model

    Attached Files: