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'74 Commando Isolastic mount issue

Discussion in 'Norton Commando Motorcycles (Classic)' started by BCMike, Jun 12, 2019.

  1. BCMike


    Apr 1, 2018
    Hey all, anyone ever have this issue. I have a '74 Commando and went to check on my front isolastic. Looked suspect so I began to remove for inspection. Bottom mounting bolt fine, top can't budge. Work, Work, Work, nothing. Can't move it. Heat, gentle hammer, nothing. Can't remove the nut without moving the bolt back. Got my impact wrench figuring I'll rattle it free. How stuck could it be? Proceeded to shear the head off of the bolt. Figured fine I'll get my impact hammer with a pointed tool on end and drive it out. Nothing. For a month now I've been dealing with this. Cut the mounting bracket off today to get access to the stud figured I could vice grip it and work it free. Nope! I'm tempted to drill it out but fear with the hardened bolt the bit will drift and F%$&-up my casing. You can see from the pics how I already chipped a hair off(kills me). Short of pulling the motor and getting it on the bench and splitting the cases any ideas? Thanks in advance ZIViIgiQQ4SBFDk8Sdn47w.jpg eUw2sRvURm2fAePfSu2Y7w.jpg
    Last edited by a moderator: Jun 12, 2019
  2. rvich

    rvich VIP MEMBER

    Jul 25, 2009
    Could you even split the cases without getting it out?

    I'm for lots of heat. One problem with banging away on it in the frame is that the motor is mounted in rubber. Get it up against something so that when you get it good and hot that you get a good solid whack.

    (I would qualify that I consider lots of heat to be 300 F or so, applied such that the entire area is heated)
  3. concours

    concours VIP MEMBER

    Dec 29, 2011
    Bolt is not hard. That said, hand drilling that far, straight is not likely.
  4. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    That is a tough one!

    What about making a bath from plasticine or modeling clay and soaking the thing in penetrating fluid oil oil or similar for a few days

    And then heat
  5. Lineslinger

    Lineslinger VIP MEMBER

    Feb 26, 2017
    Pull the engine, strip it down as far as you can then take it to a machine shop.
    Save yourself some grief and money by eliminating any further damage.
    Dances with Shrapnel and baz like this.
  6. jbruney


    Jan 5, 2019
    To stay on the safe side I'll go along with the machine shop motion. If not heat it and let it cool completely several times to let it soak and break up corrosion. Then tap back and forth to get it moving, but don't crowd it.
    I wouldn't want to bang on it whilst the case is still hot, also as it cools heat goes to the bolt expanding it. I'd allow ample cooling. That's just me..YMMV.

    IF you heat go to welding supply & buy a temp stik. 300-350F. Or quick kick to the shop at far lower risk. I know I know...but the potato is hot.
  7. MexicoMike


    Jan 31, 2010
    WOW! What a PITA!!! At this point, despite my usual nature of, "by God, I can fix this myself," if (plenty of) heat/penetrating oil didn't work, I'd give up and do as other have suggested and strip the engine down and take it to a machine shop. :(

    When you get it back, anti-seize is, of course an absolute must, especially for steel into/through aluminum (or through that similar metal, aluminium) :)

    Good Luck!!!!
  8. kommando


    May 7, 2005
    If heat will not do it then its dismantle and take to machine shop. When you do the heat then heat the alloy and not the stud, cool the stud ends if possible before starting to hit, you want the alloy to expand greater than the steel to break the bond.
  9. lardygitTVR


    Dec 3, 2011
    I had the same problem years ago when the engine was out of the frame. I tried heat with a blowtorch and hammering which didn't do much, then I drilled four small holes in the crankcases down to the bolt and spent days and days squirting all manner of anti-seize chemicals in the holes alternating with loads of heat and loads of more brutal hammering (making sure the cases were as well supported under the lug as I could make them). Eventually it moved though it took a small chunk out of one case on the mating surface, I had that welded then I filed the outer bit of the lug back to shape and it's fine now. I can honestly say it was an utter b*st*rd of a job and I should have taken the engine to a machine shop but idiocy and pride prevented me ha ha.

    Good luck, hope you get it sorted.
  10. baz

    baz VIP MEMBER

    May 26, 2010
    Often you can get studs like this out by welding a nut on the end
    The heat/ expansion and contraction often breaks
    the grip of corrosion
    Don't ever use anything pointed to drift a bolt out, always use a parallel drift
    Also use a bfh , a lead one is preferable
    Don't use a small hammer because pecking at it will make matters worse
    You need the momentum of a big hammer
    concours likes this.
  11. BCMike


    Apr 1, 2018
    Thanks all for the ideas and support. I know that the strip down and machine shop is the smartest idea and in the end will probably be exactly what I will do. This has been a bear. A routine inspection turned into to his nightmare and the worst part is the isolastics were actually in great shape and probably had many more years in them. I'll update when I finally get it figured out...Cheers
  12. jbruney


    Jan 5, 2019
    I'd not feel low for I've been wrestling 45 yrs. of stuff assembled on mine without anti-seez having been used. The Al areas are by far the most difficult. Have had some luck with heat & some backfires also, so's I lean more to the shop rather than primrose path. Good fortune in your endeavor.
  13. Craig

    Craig VIP MEMBER

    Dec 20, 2005
    Yes , good luck , when I first saw your post that’s exactly what I thought too , just nasty .... but you will win through perseverance !
  14. baz

    baz VIP MEMBER

    May 26, 2010
    Better to sort it out sooner rather than later
    It's just aswell you found the problem because it would only corrode more
    Best of luck with it
  15. Onder


    May 11, 2010
    So often doing it the long right way is shorter than the short way.
    Machine shop it is...
    998cc and Craig like this.

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