Lower norvil isolastics?

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Feb 20, 2008
I upgraded to the norvil adjustables, Im happy but wondering if anybody outhere has found the perfect adjustment for smoothness?
I have mine set at ten thou, it handles like its on tracks, but on the highway the vibes are to much for my bones. For safety reasons Im asking how far out (20, 30 etc.) can I go where it wont get real snaky?
I don't bother with all that measuring stuff with my vernier isolastics, I do as Norvil instruct below;

Taken from Norvils tech talk;
To adjust either unit, when fitted to the machine, loosen one of the ¼” UNF nuts on the through stud. This will release the adjuster, which should then be fully screwed in, (the abutment with the 2BA grub screw should be left fully tightened at all times). Now, loosen the adjuster by approximately ½ turn, which will automatically set the gap. Finally, retighten the ½” UNF nut to 25ft/lbs to complete the adjustment.

After adjustment, I usually check that the carrier isolastic end cap will still spin/turn by hand and is not locked solid , when the through bolt is tightened.

If your bike is vibrating too much, then just back off the adjuster say 1/5 of a turn more?
Interested to see Reggie using the Norvil procedure. I tried that and ended up with a huge gap, around 0.015 to 0.020". I since had the tubes squared off but still got the lower figure. Mine are set at .010" with the adjuster screwed in hard and backed off 2 holes front (1/3 turn)and 3 holes rear (I still get a buzz at 4000 rpm which is worse thru the gear lever. Thinking maybe a bent mainshaft.
If MCNS is already at 0.010" and it's high speed vibes that are the bother I wouldn't go much more than 0.012". Even at 0.010" mine felt a little 'rubbery' until I made a Taylor type headsteady. That really tightened things up but surprisingly didn't increase vibration.
Try increasing the front first, then the rear and see what makes the biggest change. In my experience a tight front really puts the high rpm vibes up.
an issue that I found and dyno Dave's site confirmed is that the rubber is a LOT harder than the original.I modified mine by narrowing the main buffers and it softened it up quit nicely. I ride mine anywhere from 100 to 650 mile's at a time and at 4000 RPM it is SMOOOOOTH.

My Norvils seem quite soft last time I looked but was thinking about narrowing. How much did you remove from all 5 rubbers? Didn't someone try drilling the rubbers also? I read that somewhere. Thanks.
I removed about 30 percent of the width on the two outer rubbers ( the large diameter ) I think dyno Dave was thinking of trying drilling them.

I had my mainshaft put on a lathe, it was under half a thou. Besides that the whole tranny and primary is slicker than I remember, so tomorrow I will loosen of thr front by a third turn.
In the back of my mind because I went to 20 thou over with pistons should I have gotten the crank balanced?
The Commando will stand quite a bit of variation in crank balance, certainly more than a little extra piston weight.

If the isos have ten thou clearance, it is reasonable to assume that the vibration is not being transmitted via the end plates.

Hard rubbers could be a cause.

You haven't said which head steady you're using. Have you gone the Norvil route there as well ?

As Keith says, a rose-joint head steady will tighten things up without increasing vibration. In fact it will transmit less than a Norvil type.
Keith1069 wrote
Interested to see Reggie using the Norvil procedure.

Yes it has always worked for me. I did once think that things were a bit slack using this proceedure, and so adjusted out a bit less than Norvil recommended, and then I instantly got a lot of vibration, and drew the conclusion that it was about spot on. As I said, I don't bother with the feeler gauges, just check that there is play on the end cap.

Keith1069 wrote
Even at 0.010" mine felt a little 'rubbery' until I made a Taylor type headsteady. That really tightened things up but surprisingly didn't increase vibration.

Interesting about the head steady. The handling on my Commando is OK, not up to modern day standards for obvious reasons, but I think I might try one of these Taylor head steadies, and see if I notice any improvements.
Yes I am using the norvil head steady, I am using only one shim so I have about 20 thou up there and thinking of taking that shim out. I did set the front lower out to 20 from 10 thou today but something came up and I couldnt get out.
If all fiddling around doesnt do it Ill just put the old head steady on and see if that helps.
Exactly how do you narrow the rubbers on the isos and still keep it square?
I have to say that whilst the Norvil type headsteady provides an admirable chassis stiffness, for me personally (a bit of a lightweight) the thing let so much vibration through that I couldn't counter-steer anymore. I suspect this varies from bike to bike and occurs mostly if there is an alignment problem pre-loading the steady in one direction or another but I'm damned if I could find it.

The obvious solution for this bungling amateur and compulsive tinkerer was to try something different :)
Just finished putting new MkIII iso's in the cradle and the front mount but noticed that the rear is made of a little softer rubber than the front. Should they be the same? I purchased them from RGM. Bike is a rebuild from tires up so I have time if these should match. Thanks guys, Chuck. :?: :?:
mcns said:
Exactly how do you narrow the rubbers on the isos and still keep it square?

I put the tube assembly in the lathe and used a die grinder with a cutoff wheel. It was a messy job but it worked. another less messy way would be to freeze the rubber in dry ice than machine it.

PS this is on the front and not the rear mount. I left the rear as bought.

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