Saving the Rears Iso's?

I have been thinking about the rear iso's (dangerous territory... I know!)

The front ones are good - especially now that I have fitted one of the Mk3 head-steady springs. Each service I loosen the bolt and check that I can slide it back and forth by hand. Means that the front ones aren't preloaded vertically.

The rear ones are a different story - and more complicated.
1. When on the road the rear of the cradle is probably trying to sag down, under its own weight, between the front iso's and the rear axle.
2. On the centre-stand the iso loads will be reversed, pushing up to support the rear of the bike - back wheel off the ground

The bike spends most of its life in mode 2 - so I was thinking how the relieve this load.
If the bike is lifted by a small scissor-lift (jack) immediately in front of the centre-stand, the loading scenario would be the same as mode 1 above, albeit with the rear wheel off the ground.

I guessed that this might be less vertical load than when on the centre-stand so decided to test it.
I loosened the nuts on both sides of the rear iso's and, in stages, tapped the stud back-and-forth as I gradually raised the jack - expecting there to be a "sweet spot"
What I found is the stud slides most feely when both wheels and the centre-stand are off the ground.

Does any of this really matter? Maybe not - but reducing static load on iso's can't be a bad thing.
So, I'll be using the scissor jack more often.
Cheers

Hi Rob, Im new to norton bikes , I am a first timer, just doing the swing arm bushes and clamp mod , rear wheel bearing , and I suppose it's the time to slot the rear iso in, I can lift mine with a gantry, hope that isnt going to be too bad , sheds a bit messy . Cheers .

Have you tried it with a paddock stand for the rear?

gortnipper said:

Have you tried it with a paddock stand for the rear?

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If you're asking me - no, but that will also simulate mode 1 (better and lower loading than centre-stand)
I used the scissor jack because I could vary the lift gradually.

Hi , don't want to hi jack robs post , but might help him to , can the guys chime in on the rear iso replacement , mine is mostly apart now , so can I just disconnect the top unit , lift the rear of the frame , not sure if there is carb to air Cleaner clearance ? Or just remove rubbers and front plate of air Cleaner, Which will let the cradle pivot down exposing the iso ? .

Shelby-Right said:

Hi Rob, Im new to norton bikes , I am a first timer, just doing the swing arm bushes and clamp mod , rear wheel bearing , and I suppose it's the time to slot the rear iso in, I can lift mine with a gantry, hope that isnt going to be too bad , sheds a bit messy . Cheers .View attachment 99048

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Depends on how you rig the lift.
Definitely seems a bit overkill to me

robs ss said:

Depends on how you rig the lift.
Definitely seems a bit overkill to me

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They were going to throw it away at work , I put my hand up , they delivered it with a ½ tonne block , it's what I have , I will just soft strop the rear frame .

Rob,
Front Iso
You say you loosen the bolt so that it slides back and forth.What bolt are you talking about and how tight are you setting the MarkIII spring?
Thanks,Mike

YING said:

Rob,
Front Iso
You say you loosen the bolt so that it slides back and forth.What bolt are you talking about and how tight are you setting the MarkIII spring?
Thanks,Mike

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If the Mk3 suspensory spring is adjusted to remove the loading from the front Iso. then the through-bolt should slide easily back and forth.

L.A.B. said:

If the Mk3 suspensory spring is adjusted to remove the loading from the front Iso. then the through-bolt should slide easily back and forth.

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Thanks Les,
Then should the spring be adjusted so that there is no load on the front iso?
Mike

YING said:

Thanks Les,
Then should the spring be adjusted so that there is no load on the front iso?
Mike

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Yes, that's the idea.