Shimming the Isolastics- A question

I am shimming the isolastics on my '72 Combat. I chose not to spend the money on a vernier conversion, so am working with the original design. Everything I've read indicates that the goal is to have a total clearance of .010". This makes it fairly tight but everything can spin freely. So here's the question: With available shims I can work in increments of .005". I set the first one up and can choose between .008" or .013". I'm leaning towards .013".... or should I go to the trouble of grinding down one of the internal tubes and try to remove .003"? Overthinking it perhaps? Thank you for your time.

I like the conversion , $ well spent , much easier to use , anyway for me I would try the smaller one first , if not for you try whatever you think best until you find the magic …..

Definitely no to any grinding of the tubes. Just give it a go at the higher clearance see how she goes, make further adjustments if needed.

What is your riding style?
Do you have the stock headsteady?
If you are a scratcher go for the 8thou

I’d go for 8 thou for sure. It is still going to allow movement, but will reduce sloppiness.

At the end of the day you’re talking a few thou either way… and this is a Norton…

Thanks to all for your input. I think I'll pull back to .008" and be careful to confirm I've still got movement once I get the engine back in the frame. I don't plan to ride this bike all that much. I probably won't put much more than a few hundred shakedown miles on it. Then I'm planning to sell it as a good runner, ideally to someone a bit younger than most of us. I always like to see some younger blood get into the vintage bike game.
As for riding style, I've slowed down plenty since I attended both Keith Code's and Reg Pridmore's track schools many years ago. I do at least one or two interstate tours per year, and a fair number of day trips on my Harley. I'm at the point of watching for clues that it may be time to hang it up, unfortunately.

Just curious - what was the price difference?

Even at minimum wage, you'll make that up with one more adjustment, I expect...

I actually didn't even do the math, just made up my mind to go the way I did. With my mechanical capabilities, the top rate I can command is about $.05 per hour, so that's not a factor.

I have ran my 1969 Fastback for 40 odd years. The clearance on the iso`s is- if you can just turn the shim with your fingernail,go riding.

I have the vernier version, as it's a mk3. I had vibration below 2600rpm, but was not totally happy at revs above that. I was planning to adjust the verniers, but tried tightening all the engine mounting hardware first. A couple of the bolts / nuts weren't fully tight, particularly the front Iso bolt. That fixed it. The difference was night and day.

Mart UK said:

I have the vernier version, as it's a mk3. I had vibration below 2600rpm, but was not totally happy at revs above that. I was planning to adjust the verniers, but tried tightening all the engine mounting hardware first. A couple of the bolts / nuts weren't fully tight, particularly the front Iso bolt. That fixed it. The difference was night and day.

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Good point.

Engine to cradle fasteners should be checked once in a while on a Commando.

If they come loose, the cases can / do crack.

If the cradle has been powder coated, check them more regularly.