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Rear Isolastic Help

Discussion in 'Norton Commando Motorcycles (Classic)' started by FreeRadical, May 17, 2015.

  1. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    Hello everyone,

    Can someone please point me in the right direction on how to replace the rear isolastic without removing the engine and transmission? It seems like I may have to remove the front engine mount. I just finished replacing it with vernier style and it was a bear to squeeze in there. The thought of taking it out again makes me want to cry!

    Thanks,

    Kevin
     
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
  3. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    Thanks for the info; however, after reading both threads I need some clarification. Not sure I mentioned this before, but I am replacing the old style with newer vernier style isolastics.

    From the first thread:

    Thanks again,

    Kevin
     
  4. Anonymous

    Anonymous Guest

    Hi FreeRadical.
    When I upgraded to vernier with single long tube I pulled the gearbox+ then took the cradle etc out through the rear of frame. Upside is you won't need to pull the front iso off again.
    Ta.
     
  5. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    I've read where one guy suspended the motorcycle. Would doing this, removing the triangular metal iso piece and supporting engine with car jack from the bottom do the job?
     
  6. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    Scratch that idea. The ceiling mount to hold the motorcycle in the air (i.e. the garage door opener supports) is not going to be strong enough. :roll:

    Next idea???

    Kevin
     
  7. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    I have replaced the rear iso on three Commandos, takes a couple of hours, fiddly but not difficult and very little needs to be removed.

    you will need a small jack and piece of wood to put under the engine to lever it up and down a tad in order to freely remove the
    long iso bolt itself, there is no need to remove the gearbox or primary, etc, I think I removed the right side little shaver charger

    because the top edge of the primary partially blocks things it is easier to remove from the right side

    floor jack in place and just supporting the cradle between engine and gearbox remove the big nuts on either side of the long iso bolt

    if things are galled in there you will need to tap each side of the long bolt to get it to freely move, back and forth, side to side tap

    I wrote a write up on the procedure for Brit Iron in the late 90s but Kenny Cummings wrote a better one up later, do a search.

    Do not fear this job, it is common sense
     
  8. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    OK, I blocked the engine up from the bottom using a car jack. I got the old isolastics out with a little persuasion and installed the new threaded rod with the integrated rubber mountings. That took a LOT of persuasion because I was installing it at an angle.

    Now here's where I'm stuck. I don't see any way to get the collars on the end of the threaded rod. With the engine supported and the top isolastics removed, I still cannot get enough clearance by shifting the frame up without hitting the primary drive case. I took the head steady off to see if it would make a difference in either direction with no luck.

    I'm starting to wonder if this can be done without removing the primary drive. Please let me know if I'm missing something here. Thanks!!!

    Kevin

    p.s. here's the kicker - the old rubber seemed fine; just the boots needed replacing. Ugh!
     
  9. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    well, as a I mentioned I have done the job on three commandos without having to touch the primary

    it takes two guys

    you should be able to solve the problem of getting the collars in place by having one guy on the right side putting his hands on the right side upper cradle by the iso stuff there and pull hard towards himself braced so the entire bike does not move, this moves it enough for the other guy to slip the left side collar in place
     
  10. ntst8

    ntst8 VIP MEMBER

    Joined:
    Feb 14, 2004
    The method below was posted on the INOA List by Mike Taglieri, worked well for me working solo.

    Subject: Easier Way to Rebuild the Rear Isolastic

    The standard workshop manuals for the Commando generally tell you that the rear Isolastic mount can be rebuilt only by removing the engine, or even the entire power train. Today, helping Chuck Contrino rebuild the rear Isolastic on his '72 Interstate. I was finally able to test a procedure I've been contemplating for a long time that lets you rebuild the rear Isolastic without significantly dismantling the rest of the bike. It worked very well, and this is how you do it:

    1. Remove the tank.

    2. Remove the primary (optional -- see below).

    3. Remove the horn (optional -- see below).

    4. Remove the air filter(s) and the exhaust pipes.

    5. Put the bike on the centerstand and fasten the centerstand with safety wire, electrical ties, bungee cords, etc., so it cannot possibly collapse. Do not fasten it to any part of the frame, but only to the engine plates or some other part of the bike that hangs on the Isolastic mounts.

    6. Slightly loosen the nuts on the large central bolt that runs through the rear Isolastic, and also loosen the nuts on the headsteady.

    7. Put a small hydraulic jack, etc., under the middle of the left frame tube (with padding to protect the frame) and slowly raise the side of the frame until the left foot of the centerstand just leaves the floor. At this point, the weight of the frame does not rest on the central bolt of the rear Isolastic, and you can remove it easily. Using a suitable drift (a 1/2" socket extension works well), tap the big bolt loose, catching the various metal parts of the Isolastic that fall free when it's out. (By the way, using a hydraulic jack this way is also useful for getting the bolt back IN when you're done, and you can look through the hole with a flashlight and move the frame until the parts are exactly aligned).

    8. Lower the hydraulic jack. Now the frame is hanging on the powertrain by the front and top Isolastics, and the top Isolastics show it by twisting slightly under the weight. Lift the rear wheel (with a 2x4", brick, etc.) until the top Isolastics are no longer twisted. Now, remove the side plates of the top Isolastics. (You do not have to remove the engine steady from the top of the engine).

    9. The powertrain is now resting on the floor, held up the centerstand, but it's attached to the rest of the bike only by the front Isolastic. Now, put more stuff under the rear wheel to raise the frame until the centerstand almost comes off the floor.

    10. At this point, the frame tubes are out of the way and the rear Isolastic is completely exposed on both sides for rebuilding.

    THE "OPTIONAL" STEPS: If you didn't remove the primary, the Isolastic is completely exposed only on the right side, and you will need some kind of hook to pull the rubber parts out. If you didn't remove the horn, the frame tubes will be partly out of the way but not entirely. I recommend taking off both of these items if you're removing the original Isolastic rubber parts, because if they're truly stuck in there, it's a %$#@ of a job to get them out. On the other hand, considering how awful a job it is to remove the horn, you may want to try this first with the horn in place and remove it only as a last resort. (By the way, if you pound on the central rubber with an ordinary drift to get it out, the rubber absorbs the shock of the hammer blows before they get transmitted to the edges. The best way is to pound on the edges of the rubber by using a very large socket on an extension as your drift).

    REMOVING THE HORN: As anyone knows who has tried it, this is one of the ultimate bastard jobs on the bike. You can do it with the rear wheel in place by unbolting just the front part of the rear fender (two bolts near the top, two nuts on studs near the bottom), and flexing the fender enough to "pop" it off the studs and move it down. These studs turn out to be the bolts that hold the horn mount, which you remove (teaching children in the area several new words in the process). Finally, you can squeeze the horn out of the space between the frame and the fender -- moving the rear axle as far back as you can will help.
     
  11. Towner

    Towner

    Joined:
    Feb 22, 2013
    Hi,

    you have to get it like this:
    [​IMG]
    [​IMG]

    Ralf
     
  12. nortonspeed

    nortonspeed Guest

    "Not sure I mentioned this before, but I am replacing the old style with newer vernier style isolastics."
    Towner did you really manage to fit the complete rear vernier style MK3 isolastic this way or did you only replace the existing pre MK3 isolastic :?: As far as I remember you have to dismantle the complete primary to lower the cradle even further to fit the MK3 rear isolastic.
     
  13. Dennis C

    Dennis C

    Joined:
    Aug 18, 2013
  14. Towner

    Towner

    Joined:
    Feb 22, 2013
    Sorry, you're right. With the primary in place, you can't lower it enough to get the MK3 isoalastic in. What you can see is the lowest position with the primary in place. I mounted the old MK2 isolastics. Once adjusted it needs not much maintenance.

    Ralf
     
  15. spelky

    spelky

    Joined:
    Oct 4, 2009
    And when you come to put it all back together find a better place to mount to horn
     
  16. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    Thanks for the confirmation, Ralf. This was my suspicion as well. I ordered the parts to remove the primary yesterday. I hear it's a pretty easy job to take it off, though I've never attempted it.

    -Kevin
     
  17. Towner

    Towner

    Joined:
    Feb 22, 2013
  18. FreeRadical

    FreeRadical

    Joined:
    Dec 5, 2014
    Thanks, Towner -- just what I needed!

    Kevin
     

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