How to adjust those isos?

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Apr 15, 2004
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My Hemmings vernier collars came in. I've got the front mount sitting on the bench, all cleaned up and ready to reassemble. But now I'm confused. I've read several conflicting methods for setting the clearances. Some say to just measure the designated side (left for front, right for rear) and adjust as required. Others say you have to measure the total clearance and that means measuring and adjusting both sides. And a third method calls for measuring total clearance but just at one side, using big freaking prybar to shove the engine over and take up the clearance on the other side. (hopefully without breaking something!) So what's right?

Also, the instructions say to remove all the shims if possible when installing the vernier collars. But with the shims removed and new PTFE washers installed, and the center bolt torqued, I've got .050" clearance on each side. Shouldn't some or all of that be shimmed out? Should I shim the right side to zero clearance? Or should it have a little?

I'm not a mechanical engineer but it seems to me there should be a little clearance on each side, preferably the same. Or will the mount center itself when you install it and torque it to spec? But if I did allow it to "self center" wouldn't that force the engine/swingarm/wheel out of alignment resulting in sub-optimal handling?

Sorry for the long post! TIA,

confused as usual

You may get 5 different answers to this question.
People all have their own experiences with different bikes.

My method is to have "0" clearance when you first assemble.
It will settle soon enough & then you can "try" different clearances until you find that "perfect" setting for your particular ride.

This method has always worked for me.

Isolastic adjustment

Hi Debbie,

There really isn't a right and left side when adjusting since the whole isolastic mount moves side to side on the central mounting stud or bolt. You should adjust total clearance at one side. I don't use the vernier type on my '72 as the shims don't really bother me. The front mount is easiest to do when off the bike and in a vice.

With the vernier adjuster I agree you should start with zero clearance then back off to what you want. That's the only way to crimp down all the parts first. You should not have to use shims with the vernier setup. If you can't get to zero clearance something else must be wrong. Are you using new PTFE washers?
Yes, the PTFE washers are new. I don't see any obvious signs of wear in the parts so I don't know why the clearances are so large. I'm thinking some shimming will be good so I don't have to crank the vernier down so hard.

BTW do they mean it when they say to use silicone grease? I'm having a hard time finding it. Would normal grease work ok or will it cause problems? I did find a tube of "plumber's grease" at the hw store but don't know if it's silicone, the package doesn't say. The stuff is translucent with a yellow-green color. Does that sound right? I have so much trouble finding all these oddball supplies at the hw store! Drives me crazy.

adjusting Isolastics

It couldn't hurt using the shims.

I get a little packet of silicon grease with new disc brake pad kits from Ford or GM. There's always more than needed, so that's what I use on the shims in the isolatics. It is sort of clear. The only reason to use this is to keep the rust out and the silicon grease doesn't attack the rubber.
Look for di-electric grease, it's normally silicone grease.

I have Mk3 style iso's in my '72. I set them up with 0.008" clearance at the tightest spot on the diameter, using a feeler gauge and the prybar method. I check the clearance once a year.



Ditto the use of di-electric grease; you should be able to find it at most auto parts stores.

I'm confused about your gap problem and the fact that you have to "crank down on the vernier so hard." You should be able to snug up the vernier by using a small punch or round bar. Simply insert the punch or bar into one of the holes in the adjuster and pry clockwise.

The tighter the adjusters, the sharper the bike will handle. However, this sharper handling has a price: increased vibration. And this vibration may cause some fatigue failures. For instance, one of the mounting tabs on my oil tank broke from vibration induced by a too-tight iso.

Finding the optimum adjustment may require some trial and error, letting the seat of your pants be your judge.

Silicone grease is available as "stopcock grease" from scientific supply houses. It is also available from scuba dive shops as lube for o-rings on regulators or cameras. This source is the most convenient for the non-science employed. Online you can order from Leisure Pro ... D=AQUSG125

It doesn't take a lot, so a tube will last many years.
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