MK II Rear iso rebuild

I want to renew all the rubber parts in my '73 850's rear iso. There is a vernier adjuster in place by the PO. I don't know whether it's an aftermarket adjuster or one from a MKIII. I have read all the info re doing this without the disassembly covered in the Norton service manual but I have a question. The following is a quote from the method described in an archlived post by Mike Taglieri:

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.

I don't understand the above. If you raise the rear wheel it appears to me that the frame will not move, the engine/swingarm/plates/centerstand will move (upward). If you move this assembly up so that the centerstand almost comes off the floor, what's holding the rest of the bike upright? Maybe I'm just having trouble visualizing it and if I just did it, it would become obvious but it doesn't sound right to me. It seems that SOMETHING has to be holding the bike's frame upright while you jack up the engine/centerstand plates. OTOH, if you removed the shocks wouldn't the bike frame (rear fender) just tend to sit onto the rear tire which would accomplish the same thing (making the iso mount clear the frame tubes) without "lifting" anything?

I apologize if I'm just to obtuse to understand the instructions but Ive read and re-read the article. I then thought maybe if I got looped, that might help (OK, it was actually just an excuse to get looped). But both sober and looped and I still don't "get it."

Any explanation or reference to other material would be greatly appreciated.

I recently did this and this is what I had to do to make it work. I first replaced to front Iso. It sounds like you don’t need to do this so I will skip over it. I put the bike on a bike jack that supported it under the frame tubes but was open under the cradle. I then ran a tie-down strap around the rear iso tube and up over the backbone tube. (I had the battery box out at the time, I don't know if you could do this with the box in place, you would have to look). I put tension on the strap to unload the Iso and withdrew the bolt. You can then drop the engine and cradle assembly down, hinging on the front iso, until the inner primary case rests on the frame tube. In this position the rear iso tube will be about 85% clear and you will have enough clearance to remove or replace the old style multi-piece isos. I think this is the position that is referred to in the article you sited. However, you (or at least I) will not be able to get a MKIII style iso in due to it being all one piece. You can get the rubber bonded part in with one abutment installed but you will not be able to get the other abutment on because of the length of the tube. The tube will clear the iso mount flange but you will not be able to screw on the adjustable abutment because the flange will be in the way. If you were to remove the primary you could drop the motor and cradle assembly down a little bit farther and completely clear the rear iso tube. If I had to do it again I would probably do it this way. But, I don't have a puller (yet) and so couldn't remove the whole primary drive. So I ran a second strap around the front iso tube and over the small tube the head steady bolts into. I tensioned the strap and withdrew the front iso bolt. I then tightened the front strap and lifted the front of the motor about 2 or 3 inches. I was then able to shift the whole motor/cradle/swingarm/rear wheel assembly forward in the frame far enough to clear the rear iso. Once the new rear iso was installed I shifted the motor back, lowered the front back down and reinstalled the front iso bolt. I was then able to lift the rear iso into alignment and insert the rear iso bolt. I did have the head off when I did this. I think I would have had the clearance with the head installed but I'm not sure. I was also able to do all of this without any help and without doing anything to the rear suspension. This is just the way I did it, I am fairly inexperienced and there may be a better way.

Hi Mike, I am right above you in Albuquerque, New Mexico!
I have a 73 850, and three months ago replaced the rubber donuts in both front and rear isos.
No need to touch anything on the primary.

Twice now over the past 15 years I have replaced them, and both times did the rear entirely in the frame.
It is not difficult at all. No big deal, do not let it scare you.
I put the bike on a lift just so I could be standing up working on it, off the centerstand, held by the front wheel vise.
But, I have also done the rear on the sidestand only, both instances using a small floor jack under the engine plates to support the rear.
You are welcome to call me with any questions, my number is area code 505, then 459-5494.
Remove both nuts from the main stud on the rear, have a jack keeping slight upward pressure on the engine plates rear of the motor.
Remove head steady.
With a wood drift work the main stud back and forth, hope it is not galled in there, I had to use penetrating oil and slowly work in for a couple days the first time.
With the stud out, working from the right side remove the spacer, shim, end cap, etc, then remove the end rubber donut, a little fiddly to get out, but not bad.
Remove the left side end everything and remove the big end rubber donut.
Remove the inner rubber small donuts.
Clean the iso cradle good, and try to lube it and the new rubbers with silicone spray lube, silicone will not deteriorate the rubbers.
Put the new rubbers in from each side, you will need an assistant to grab the cradle plates to pull the unit to one side to while fitting the other side's threaded
iso adjustor.
Give me a call, I can give you ideas along the way, do not be afraid of this, two people takes about two hours to do the rear, all in the frame.
John

Thanks guys - great stuff!!!!

I recently took mine apart. I had the head steady off, put the bike on the center stand and then lifted the back of the frame by using a come-along on the grab bar. I lifted until the center stand was just starting to lose contact with the floor. This allowed plenty of room to drift the bushings out with a piece of PVC pipe.

I've believe I've discovered that the vernier adjuster which was installed on the rear iso of my MK II by the PO is the MKIII adjuster, not an aftermarket adjuster (like Hemmings, etc) A pic is below - so please verify if my "discovery" is correct and that it is, in fact, an oem MK III vernier adjuster. It seems to match the parts book pics. If so: In looking at the parts book for the MK III, it does not show the individual donuts as it does for the MK II. So...I assume one orders the entire "Isolastic Bush Assy, Mk3, Rear" as shown on Old Britts. Is there any other better parts or recommended way to do this other than putting in a new bush assy. The old one is not in bad shape, unlike the front which was absolute mess, but the donuts are compressed rather noticeably off center.

I pulled it with the bike on the side stand. I had to pull the inner chaincase but that was no big deal because I was going to do that anyway. Thanks to all the instructions from you guys, it was quite easy and took maybe 90 minutes from start to taking the picture of the mount.