At Wit's End - No clutch feel, can't engage clutch from lever

Discussion in 'Mechanics Garage' started by supersecrettechnique, Dec 20, 2018.

  1. squirrelman

    squirrelman Member

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    in difficult cases you can try bleeding from the bottom up, injecting fluid into the slave bleed fitting.

    in this case i suspect bad seals in the mc rather than a trapped air problem.
     
    Last edited: Apr 21, 2021
  2. ridervfr

    ridervfr Member

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    When I started restoring these bikes and came to the clutch system, I found that replacing the slave cylinder was a better option for me. I get parts at a discount and it was not worth doing the rebuild kits. That being said, those slave cylinder right out of the box had weepage around the bleeder nipple out of the box! It was not enough to affect the bleed process mind you, but it was there. If left untouched, it would have lost fluid I would imagine. I ended up using a thread sealing compound on it, (not teflon tape) and let it be. I had these HEL bleeder nipples that I used for my bikes brake systems and was planning on using one when I did the clutch bleeding. When I over-hauled one of my 750s front calipers, I had weepage around the bleeder nipples, and my recollection serves me that I had problems getting a bleed. The bleeder nipples are stainless steel and are part 66M-BNM8x1.25. I think the US outfit is out of biz due to the virus. I did however order a stainless rear brake line for my 750 from the UK outfit online.

    I replaced the all the rubber lines with stainless lines on all my bikes. If you had a real problem on the slave cylinder, it would be a mess there. Think about investing in an air assisted bleeder that hooks up to an air source where you can create a good vacuum on the bleeders. Maybe your line is bad. Look at the bright side, its not a linked brake bike (thank goodness) Peace :mech:
     
  3. dgp

    dgp New Member

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    Thanks guys, I do have a vacuum bleeder, I called it a compressed air bleeder in my post which may have been confusing.
    I also forgot to mention that I did try the reverse bleed, but still no joy. My next step is to go out today and buy some circlip pliers that can access the clip in the master, pull it apart and check the seal and bore.
    Thanks for the ideas.
    Thanks for the bleeder nipple dimension @ridevfr, I might see if I can pick one of them up too, and I might just smear a bit of silicone grease on the thread for a better seal.
     
  4. squirrelman

    squirrelman Member

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    a good test for the mc seals is to run a proper-sized bolt into the banjo bolt hole (after a bleed there) and test that it builds and holds pressure.
     
  5. dgp

    dgp New Member

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    Thanks squirrelman this will be on my list too.
     
  6. dgp

    dgp New Member

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    Righto, followed squirrelman’s advice and used a bolt in the master cylinder to see if it was holding pressure. Sadly no, no it wasn’t.
    Pulled the master apart, and found that the bore was quite bad, it looked as though the previous owner had let the fluid drain out and dry up in the bore, leaving corrosion spots.
    So, I got some 2000 grit wet/dry sandpaper, wrapped it around a 12mm fuel hose, covered it in brake fluid and deemed out the bore. It looks heaps better but only time will tell.
    I need to buy some silicone grease tomorrow and re-assemble the system to see if it will hold pressure.
    I have attached some before and after pics below, sorry, not the best quality.

    Thanks for all the suggestions guys.

    B4D1CE92-BFEE-4ACB-8481-4A7162E4EFE7.jpeg 278B337A-194F-4CA1-B9C2-9400BF015947.jpeg 74CD61E1-4E33-4FD8-960D-894CEBB16EE0.jpeg E8BD767D-BCEC-4187-B4C8-87B7A7B1AC03.jpeg
     
  7. Simon Edwards

    Simon Edwards New Member

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    When I did that I then went up in grades P3000, P5000 to P7000 grit. After that I used brasso (yes, really) to get a properly polished finish. I used strips of brasso fibre wrapped through a plastic spiral brush on a battery drill for about a minute on a slow medium speed. This polished result usually lasts ages.

    Don't forget that whatever you do to polish inside there you'll need to thorougly clean out the residue left afterwards using brake cleaner.

    Having done the MC I recently used this approach to restore the piston in the clutch slave as well as on the slave's bore. It has a nice smooth pickup now.

    Good luck.
     
  8. dgp

    dgp New Member

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    Good tips, thanks.
     
  9. Simon Edwards

    Simon Edwards New Member

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    NP.

    I forgot to mention that I couldn't get direct access to the bore with a drill-held-brush because the chuck is too wide and gets in the way. So I used a rotary tool (think cheap generic "Dremel") 18" extension to hold the spiral brush. These have a really narrow chuck. The other usually end fits into dremel's drive socket. But in this case I just held the shaft in the drill/drivers chuck which allowed me to have slow speed control.

    I used a similar setup, but with a Dremel to drive it, and genuine brass (not brass coated steel) circular bushes to clean the bores and seal slots of the calipers. It makes that job really quick and easy.
     
  10. dgp

    dgp New Member

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    Thanks Simon, I recently bought a Dremel after putting it off for years, which I had purchased it sooner, it’s a very versatile tool.
     
  11. dgp

    dgp New Member

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    So, after cleaning up the bore with P2000 ( I live in a town of 30,000, and no one sells anything above P2000), and Brasso, I put it back together and still no joy. I dismantled it again and took the master to a machinist to talk about re-sleeping it. I also ordered a rebuild kit.
    The machinest said he had seen much worse still operating and made a point of telling me he thought the piston rubber was too flat, he thought it should have more of a tapered edge. Pic of a new one below (courtesy of CMSNL). Mine is certainly was more round, without the edge on it ( sorry didn’t take a pic before installing).
    Over night I soaked the piston rubber in my mix of wintergreen oil/ isopropyl alcohol that I used to rejuvenate my carb insulators. I did this as it is known to swell rubber. This morning, I put it back together again, piston rubber has swollen and required some grease to slide into the bore, hey presto, I now have pressure.
    The master is still on my bench, I will leave it there for a few days to see if the rubber contracts and loses pressure, but I am happy I found the issue. I also noted that there is a small tear around the sealing washer at the base of the rubber boot that contacts the circlip.
    I will most likely pull it all apart and put the kit through it anyway, just to be sure.

    670EB8F2-7866-4366-A75E-199288B11613.jpeg
     
  12. dgp

    dgp New Member

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    After a couple of days, the clutch went back to having the same issue.
    Today I received the new OEM rebuild kit, installed it and now have a working clutch.
    You can see in the photos below the big difference between the old and new seals.

    DA3045CF-8E18-4BDD-9934-72D2FFCA7C49.jpeg 61A0C8AF-79CC-4E7C-9785-6D5A227137D7.jpeg AD17FEF7-1C8D-4236-B873-CF8D6B1137A8.jpeg
     
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  13. Simon Edwards

    Simon Edwards New Member

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    Nicely done, and nice photos too.

    Having seen what the clutch seal looks like, I wonder what the Front Brake Master cylinder seal is like? And the Rear Brake Master seal too?

    I found that all three of mine were in a similar condition as they were all original components. The clutch slave seal was also similar. All simply down to age.

    In your case it wasn't helped at all by that dried up crud grinding away at the seal.
     
  14. dgp

    dgp New Member

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    You make a very good point Simon, another little project for me to tackle.
     
  15. Simon Edwards

    Simon Edwards New Member

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    It was a point originally driven home to me when my front brake lever met the handlebar late last year. Luckily a second pull restored stopping power on that occasion.

    I got very lucky. It happened when I was on a post carb' re-build shakedown test run at roughly 30mph and I had plenty of time to stop with the gears alone if I had to. If that had happened at highway speed in traffic it would have been a different story.

    Its well worth the extra effort to do the whole lot, and the calliper seals and slides too. The effect of the extra fine control "feel" that this gave to all three systems was very impressive and makes for much more enjoyable riding.
     
  16. Diving Pete

    Diving Pete Member

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    No brakes does also lead to a very exciting (and short) journey ...
     
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  17. dgp

    dgp New Member

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    So I have now also overhauled the front brake master cylinder and the front callipers, the piston/seal set in the M/C is in the picture below, and while it still was operational, I am glad Simon suggested I check it out, as the seals were definitely worn.
    I am still waiting on the rear M/C kit to arrive from Honda, but will soon be doing the same for the back end.

    9F68733B-7AF3-48C1-BDEC-6EC8C3EAB502.jpeg 88602BFF-6F4A-4A88-A76E-5C5634F487A8.jpeg
     
  18. ridervfr

    ridervfr Member

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    Nice pictures and write up! I ended up using some cottage built pistons for the rear brake caliper and must have used a donor caliper, just don't remember well as it was done a number of years ago. Once you have all this stuff done, your pretty much good to go, assuming your carburetors are all tight and right, Right? Bike will run forever. Peace
     
  19. dgp

    dgp New Member

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    Thanks ridevfr, I have already reconditioned the carbies, and done the valve shims, she runs like a charm.
     
  20. Simon Edwards

    Simon Edwards New Member

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    Great pictures. Nice job. I bet your front brakes have a lot more feel now.
     
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