Isolastics (confused)

Thanks for that Keith, there was no sign of any circlips anywhere in the assembly and no mention of circlips in any of the workshop manuals. Still don't understand why the front middle rubbers would not be a fit to the outside diameter of the internal central spacer. I did suspect that the inner rubbers were to prevent excessive movement and can see that the Mk3 type, with bonded rubbers, is possibly a better design.

Isolastic mounts do appear to be a bit of a black art, I don't believe I've read one definitive article on what is best. I think a little experimentation is in order.

Ta for that Allan, sounds to me like the isolastics don't just need adjustment in the end float, but somehow need to be adjustable for the amount of damping provided. I guess all engines will differ in the amount of out of balance they exhibit, thus requiring differing shore hardness of rubber damping to compensate.

Thanks Keith. Picture not too clear but looks as though it could be No.46, 2 on front and 4 on rear iso. Is there somewhere online I can view the original diag? I've a feeling I have mongrel rubbers on mine, I can't believe that there would be 5mm play between the rubber bore and the spacer on the front assy, even two circlips would not stop these floating. I was surprised when I stripped mine. I was expecting to have to press the inners out, but they just dropped out onto the floor. I will figure out a way of keeping the rubbers from moving if I decide to retain the original shimmed design. I should just say sod it and buy a MK3 adjustable set, however I am reading so many different views, with some saying the original design was better, that I'm just thinking hold the expense and try what I have.

Thanks Keith. Picture not too clear but looks as though it could be No.46, 2 on front and 4 on rear iso. Is there somewhere online I can view the original diag? I've a feeling I have mongrel rubbers on mine, I can't believe that there would be 5mm play between the rubber bore and the spacer on the front assy, even two circlips would not stop these floating. I was surprised when I stripped mine. I was expecting to have to press the inners out, but they just dropped out onto the floor. I will figure out a way of keeping the rubbers from moving if I decide to retain the original shimmed design. I should just say sod it and buy a MK3 adjustable set, however I am reading so many different views, with some saying the original design was better, that I'm just thinking hold the expense and try what I have.

sorry about last post done twice. I got a server error the first time i posted and then hey ho I got a double hit on the second effort.

Interestingly I have just been looking at spares on the Noc site and there is a picture of a center spacer. This looks a larger diameter than mine and has 4 circlip grooves. Maybe I just have a rouge center spacer. Elementary Watson.

Thanks for advice David, so not the mongrel I thought i had. Front spacers were a sliding fit, if you class 5mm clearance as sliding. I have bought a newer spacer with grooves for the front, so that should be sorted. Will fit a Hemmings adjuster to the rear iso as its more inaccessible. I note your advice on the engine/cradle being parallel. How is this sorted if it's not? More shims or machining?

I have just received new front iso rubbers in the post and guess what? The center front buffer rubbers have a bore of around 18mm which makes them a nice tight fit on my existing 19mm dia spacer. What the 25mm bore rubbers that came out were, is any ones guess. Anyway thanks for all contributions, mystery solved I think.

Thanks for that Henry, I did try to balance the shims when I reassembled. I have to admit however to putting the last 10 thou shim offset on the left side of the front iso, the rear being equal both sides. Will this really put the handling that far out? Having never ridden a Norton however, I have no intention of riding 'hands off' in the near future.

Thanks Henry, I'll leave be for now. It will probably need re-shimming after a few hundred miles anyway. I'll balance it then if there is a problem. If you've read my question on the front forks, I can see those being more of a problem. All good fun though, I love a challenge.