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Isolastic PTFE washer wear

Discussion in 'Norton Commando Motorcycles (Classic)' started by worntorn, Dec 3, 2019 at 7:45 PM.

  1. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I removed the front isolastic mount from the MK3 to have a look at how it is made.
    This is most likely the original iso. The original owner supplied all repair/parts bills with the bike and there are no iso parts shown.
    Total mileage from new is 27,000.
    The washer from the adjuster side measures 40 thou in the wear area and about 72 thou in the unworn area. So they do wear quite a bit!
    I've been a bad owner and never adjusted the isos, other than the head steady after removing the head early on.
    There was about fifty thou of play in between the washer and end plate, roughly ten times spec. Funny thing is, the handling was fine. The bike is also very smooth, that's my excuse for leaving the isos alone.
    The head steady spring tension was enough to hold the engine weight completely. After removing nuts, the mounting bolts slid out with fingers pulling lightly, no pressure down or up on them. That head steady spring tension is something I have played with quite a bit. Too much or too little tension really brings on vibes. It seems the neutral spot is also the Goldilocks place for vibes.
    I guess that has also helped to keep the iso rubber central.

    Glen

     
  2. acadian

    acadian VIP MEMBER

    Joined:
    Mar 5, 2010
    What is the distance from the pin to the bracket in your goldilocks spring set up?
     
  3. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Sorry I don't know, haven't got the tank off right now.
    I know it was a fair bit off the number in the big white shop manual.
    Its probably a little different for every bike.
    One could start by adjusting tension until the centre bolt in the iso is free to slide in and out, or either of the iso/ engine bolts are same.



    Glen
     
  4. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    You are lucky to have pulled the washers out with that uneven wear in one piece. I've bought bikes where they come out in pieces from zero lubrication over the years.
     
  5. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    The wear is very even, no more than +- 2 thou difference measuring various places in the contact portion of the washer.

    Glen
     
  6. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    What lubrication is necessary of the PTFE washers?
     
  7. kommando

    kommando

    Joined:
    May 7, 2005
    PTFE bushes can be run dry, but if you grease the Bush then the expected life doubled and friction is reduced. But these Isolastics collect dirt which would contaminate any grease so best run dry. I have some Graphite impregnated bronze washers to try as an alternative.
     
    Last edited: Dec 4, 2019 at 1:16 AM
  8. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    Peel back the rubber covers then spay the washers with silicone lubricant from a spray can . Washes out dirt at the same time. The rubber covers are needed on the front to help keep out the dirt but the rear iso covers are optional IMO as little dirt gets in there .
     
  9. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    I would have thought that ‘dry film’ PTFE lubricant would be best. It’s a highly penetrative and cleansing aerosol spray, and when the propellant and solvents evaporate, only a dry PTFE lubricant remains, which will not attract dirt and grit.

    It’s what I use, but I don’t do enough miles to claim to be a good test case !
     
    kommando likes this.
  10. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    I wonder how many miles this one has done! :)
    [​IMG]
     
    maylar likes this.
  11. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Wow, that looks like 100,000 on gravel roads!

    Glen
     
  12. edgefinder

    edgefinder

    Joined:
    Aug 28, 2012
    For the folks that have turned their own. If you some pex or Delrin but no ptfe which would you use?
     
  13. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    The manual suggest using a silicone grease to coat all of the wear surfaces.
    Venhills advises to not to lubricrate their PTFE lined cables with anything as PTFE does not require lubrication and all types of lubrication tend to add potential for grit.

    The boot kept things very clean so maybe this is an OK result, just tighten things up once in awhile. A new PTFE washer every 50,000 miles or so isn't a problem. I will slide some new ones in here at 27,000 but they aren't really needed yet.
    The iso itself looks good, not going to change it. Others have done so and ended up with increased vibration.
    All in all it looks like a well designed piece of engineering that does exactly what was intended.
    In reference to the " What to build thread" where it was decided to use parts for models pre 74 only, I think that is missing some real opportunities for easy improvement.
    One look at a sagged out pre MK 3 front iso vs this serviceable and still centered original tells you that the adjustable spring added to the MK3 head steady was a pretty clever idea.
    The vernier adjustment and the single tube with rubbers bonded on is also the way to go.
    I'm fabricating one of these in alloy and had another plan for the innards, but realize this is reinventing the wheel. So it will get an alloy housing but standard MK3 guts.

    Glen
     
    Last edited: Dec 4, 2019 at 9:59 AM
  14. Lineslinger

    Lineslinger VIP MEMBER

    Joined:
    Feb 26, 2017
    For the boots, rubber fittings and all metals....

    L1080211.jpg

    From my organic chemist friend Chloe...

    " Forgive my seeming ignorance here but I have read, over the years, that PTFE is essentially inert regards it's interaction with aliphatic hydrocarbons such as what one encounters with "grease. Under the conditons for this use involving light pressure and minimal torque, softening is probably not an issue or at least no more than a surface effect."
    I should think that it would be more prone to damage by abrasion, such as would be encountered if pushed up against a rough surface area. Then grease would likely act to protect the PTFE component."
     
  15. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Venhills advises against lubing their PTFE lined cables but said they realized some owners will lube anyway, not content to leave things dry. For lubing to make owner feel good but cause minimal damage to product, they recommended a spray lube that evaporates leaving a dry film.

    Glen
     
  16. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    I think it was someone on this site that put me on to this stuff initially, I use it more and more now...
    DA2DC82B-7B38-4FEC-8408-89160D7CCCF0.jpeg
     
  17. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    PTFE is polytetrafloroelthylene and is naturally slippery. No lubricant needed for these. Is the lube for the steel shims to prevent rust?
     
  18. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    ?? I put new PTFE washers in my ‘72 during the rebuild 1998. They have more than 35,000 miles and look fine and no lubing. Anyone have worn out washers with known conditions?
     
  19. Torontonian

    Torontonian

    Joined:
    Dec 28, 2009
    W
    Well I use a silicone spray but you could also use a PTFE spray. It's just easier than getting die-electric or silicone based grease into both sides of the washers (4 involved , front and back ) . I figure any lube in there is better than running them dry , but yes the PTFE washers can be run dry. Ask your expensive fry pan what it prefers ? . Got rid of shims a long time back for the vernier set ups.
     
  20. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    Speaking of vernier, how often do you find you have to re-adjust the isolastic clearance? Are you checking and setting to .010" both sides total?
     

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