Characteristics created by Incorrectly adjusted ISO (Too tight & Too loose)

Hi Guys
I Have my front and rear vernier ISO set to the spec supplied in the literature from AN. i'm curious to know what characteristic are evident when riding for both Too loose (excessive clearance) and too tight (not enough clearance) ??
I'm pretty happy with my settings, but interested to know what to expect if/when the settings go off

My understanding is that too loose and you’ll get that sloppy handling ‘hinge in the middle’ feel. Too tight and you’ll get increased vibration.

Thanks LAB. That's the criteria that I used when I set up my vernier isolastics. I found that the default settings recommended were too buzzy and backed the adjusters off "a hole at a time" until they were as I liked.

Mine doesn't do well at .010" clearance.... I believe to dump vibes and maintain no slop I've got them about .012" in front and .010" rear. .. You'll know thee sweet spot.

Like Maylar, I set mine as tight as possible. Tighten them until is vibrates in the pegs, then back them off one hole at a time until the vibration subsides. Should be vibration free above 3000 RPM.

I can tell you from experience that having too much clearance in the rear iso gives very vague handling, and a feeling that the bike has to be continuously "steered" in order to hold a line, even when going straight - no fun at all in corners.

Fast Eddie said:

My understanding is that too loose and you’ll get that sloppy handling ‘hinge in the middle’ feel. Too tight and you’ll get increased vibration.

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When racing with Isos some of us deliberately set them tight, definitely felt vibration immediately through the foot pegs! (Mirrors? )

But after all, it is what the Isos are there for!

My bike seems happiest at .008 clearance to the front and rear isolastics.
Mind you the PTFE washers , they need to be periodically greased , which is often neglected , then remember that this measurement is TOTAL clearance , not measured per each side. The way to achieve this for me is to put the machine on it's sidestand , not center stand , slacken off the 2 main bolts , push the motor/gearbox over to the left side by boot , wooden lever stick or whatever works to achieve zero clearance on the left , then measure and adjust the right side with shims as per needed. MK 111 vernier system is a different cat .

upgraded to the Mk3 vernier types on my 74 Mk2 - front and rear. set them to .010". some minor vibration at 1500-2500 rpm - less noticeable during acceleration, but fairly smooth at 3000 rpm and above. seems to handle OK. no complaints.

You've hit your sweet spot..... Ride, ride, ride.

When I got my Commando it vibrated badly at the 3k ish mark, especially when decelerating, so much so it actually felt like something was very wrong!

Whether it was hard isos (they’d been replaced by PO) or a badly balanced crank by the factory, I’ll never know. But with a balanced crank, AN isos and Comstock head steady, the transformation was staggering.

I believe the factory got sloppy with crank balancing, and different cranks require very different iso settings. Being smoother definitely allows tighter iso settings. If I’d have adjusted my iso‘s then like I do now, I think vibration would have cracked the frame!

What I now do is nip them up tight and back them off just a tad. I get a lever and pry the cradle and adjust that ‘tad’ so the cradle is able to move in the isos freely, but only just, with very little actual play in the isos.

I’m of the opinion that the isos were so successful the factory abused them. Meaning that they were so good at absorbing the vibes, the factory stopped caring about the source of the vibes, and cut corners when it came to crank balancing etc.

A well balanced Commando engine shouldn’t vibrate that much as proven by the many solid mounted specials. Seems to me the isos were designed for / work best with a well balanced engine, where all they have to do is take the edge off what vibration is left and NOT as a way of saying ‘balance doesn’t matter becasue we’ve got isos’.

All only IMHO.

Totally agree with post #8 re adjusting. I use .006 because it seems to work best on my Commando as a balance between handling/vibration BUT it vibrates a bit more than it will at .010 (factory spec).

Torontonian said:

My bike seems happiest at .008 clearance to the front and rear isolastics.
Mind you the PTFE washers , they need to be periodically greased , which is often neglected , then remember that this measurement is TOTAL clearance , not measured per each side. The way to achieve this for me is to put the machine on it's sidestand , not center stand , slacken off the 2 main bolts , push the motor/gearbox over to the left side by boot , wooden lever stick or whatever works to achieve zero clearance on the left , then measure and adjust the right side with shims as per needed. MK 111 vernier system is a different cat .

Click to expand...

I dont recall reading that the PTFE washers should be periodically lubricated??

As Torontonian said, the bike can’t be on the center stand when adjustments are made.

"I dont recall reading that the PTFE washers should be periodically lubricated??"

I don't either. I thought the whole point of PTFE in this application is that it never requires lubricant, being one of the slipperiest solids made. I recall reading somewhere years ago that it's one of the only materials a Gecko lizard cannot "stick to." Good to know in case global warming initiates a world wide gecko plague!

I use dry film PTFE lubricant.

The workshop manual says to grease everything whenever you have the iso's apart for inspection or shimming.

Re PTFE (Teflon)

From Dupont re a question about lube for a PTFE washer/spacer: "In general against a flat clean metal surface, a PTFE washer shouldn't need a lubricant to function for the type of movement implied. In fact some lubricants might soften the washer and diminish the performance."

Were the original OEM spacers PTFE? I have no idea.

Just as an aside about isolastic shimming -

I remember being very anal about maintenance when my Norton was new. The dealer gave me a choice of a cheap helmet or a factory service manual with my purchase of the bike. I chose the manual. Followed recommended shimming and kept it at 0.010 per spec. The iso's were like a switch - at 3000 rpm vibration just stopped. Thank you, Norton.

About 2009 I did an engine-out rebuild and installed vernier iso's that were given me for Xmas. I was very disappointed that the vibration wasn't as sweet as before (there was discussion here about buffers being harder back then), requiring wider adjustment to be livable. Handling was still OK, but my mirrors were a useless blur below 3000 and I do a lot of 35-50 mph riding here.

Last year I put a cNw head steady on the Commando. Not only did the handling tighten up, but as a side benefit the vibration at 2500 rpm (40 mph) just disappears. Mirrors are totally clear. I have one of the MKIII head steady springs but I'm not gonna install it - I don't want anything to change from what I have now.

With the CNW/Jim Comstock head steady I backed off the vernier adjustments until it was smooth at all revs. This head steady maintains the alignment, hence, no hinge in the middle and makes it a delight to ride.