Isolast Adjusting Screw Location

Since I had my engine rebuilt and remounted (not by me, not that I would have prevented an issue) I've noticed quite a bit of vibration and very unsettling handling. Vibration is much more and handling seems very questionable over what I experienced for the previous 4 years or for that matter before I had the vernier type. Vibration is more than just a buzz and seems to build throughout the RPM range. Handling just feels unsteady at all speeds, especially at 70-80 mph. Previously I never felt unsteady up to 95 mph or so but now!

I figured I needed to adjust the isos but when looking at the Norvil site I noticed that it says very clearly that the adjuster screw for the front needs to be located on the right side and the rear screw on the left. As currently mounted both of mine are on the left side of the bike. Does this actually make a difference? First thought is why should it make any difference. The point is to provide clearance for the whole assembly. But I figured that the statement was so clear that maybe adjusting them to open the clearnace may not address the root of the issue.

Any thoughts anyone has would be welcome. I've gotten to the point that I don't want to ride (might be a question of being 65 and becoming a chicken shit but I don't think I would feel this way without cause).

My vernier adjusters are both on the LH for ease of access.
I'll also be interested in the rationale for the front one being on the RH.
Ta.

Yes always wondered why too. :!:

I put rear adjuster on LH d/t oil tank and hoses and front on Rh d/t primary case in the way and good isolation and normal thoughtless handling. Something in a bind to conduct vibration and why I consider Commandos the thinkng mans manhood tester. The handling issue is weird report as police and racers close gap for better control at expense of nerves jangled. Cdos can be pretty skewed and still track well so to me implies something more than major alignment which would be obvious and more something sticking preventing free motion to comply with road going. Fork swing free and not locking up d/o over fill of fluid pump down of air pocket? If one piston left out the horizontal balance rock would vibe but not harm handling. This could be interesting lesion session for the rest of us. When I had rear leak get much lower than front the steering begins to fight back at me.

It depends.....

I have Mick Hemming's ISO adjusters. The both sit on the left hand side. I believe the front ISO adjuster on the Norvil and factory adjustable jobs sit on the right hand side.

Cheesy said:

It depends.....

iso-cradle-frame-alignment-t12034-15.html

Click to expand...

Hadn't noticed that thread before. From what it says that if you had to machine to accept the vernier mount the front mount adjustment should be on the right side. I know that to install the adjuster machining had to be done to accept the front mount. If my adjuster is now on the left side does that mean I need to flip it? If installed opposite should it make a difference?

The amount of vibe is such and has a linear increase throughout the RPM range which wasn't consistent with my previous experience. The handling issue may be my imagination brought on by the unusual vibration and heightened sensitivity.

Should I back off the adjusters some, front and rear, and see what happens? That's what I was going to do until I noticed the arrangement of the front adjuster.

JimR said:

Hadn't noticed that thread before. From what it says that if you had to machine to accept the vernier mount the front mount adjustment should be on the right side. I know that to install the adjuster machining had to be done to accept the front mount. If my adjuster is now on the left side does that mean I need to flip it? If installed opposite should it make a difference?

Click to expand...

The drawing (viewed as if looking from front to rear) shows the front RH 'adjustable' end cap of the MkIII vernier (the one that requires the RH end of the tube to be machined down) is significantly wider than the 'fixed' (LH) end cap.

If the end caps were reversed, it would force the front Isolastic mount over to the right, therefore putting the engine, cradle and swingarm out of alignment.

Thanks LAB. I suspect this would account for the high vibration and unsteadiness that I have been seeing.

Of course I had an aha moment but didn't really read the post completely. So looking Front to Rear, right side would have the front adjuster and left side would have the rear adjuster. If my front adjuster is on the right side, looking front to rear, it would be in the correct position. Does it matter if the rear adjuster is on the same side?

Topical thread. I too have the hemmings adjusters installed on my 71. Makes life simple.

Having no experience with the factory vernier setup, I'm wondering whether the adjuster on this unit is locked by a grub screw (like the hemmings) or by the main bolt/nut? Reason I ask is because on the hemmings unit you can loosen the grub screw and turn the adjuster collar in or out to achieve clearance without ever loosening the main bolt.

JimR said:

If my front adjuster is on the right side, looking front to rear, it would be in the correct position.

Click to expand...

The front adjuster is on the left on the drawing, looking "front to rear", which is the right hand or 'timing side' of the machine as you would sit on it.

acadian said:

Having no experience with the factory vernier setup, I'm wondering whether the adjuster on this unit is locked by a grub screw (like the hemmings) or by the main bolt/nut?

Click to expand...

= The main bolt & nut.

On the MkIII Isos. the grub screw is there to lock the non-adjustable caps (abutments) to the tubes.

Both MkIII adjustable caps (front & rear) are one-piece items, so the only way to alter the MkIII Iso. clearance is to screw the adjuster either in or out after the main bolt has been slackened.

L.A.B. said:

acadian said:

Having no experience with the factory vernier setup, I'm wondering whether the adjuster on this unit is locked by a grub screw (like the hemmings) or by the main bolt/nut?

Click to expand...

= The main bolt & nut.

On the MkIII Isos. the grub screw is there to lock the non-adjustable caps (abutments) to the tubes.

Both MkIII adjustable caps (front & rear) are one-piece items, so the only way to alter the MkIII Iso. clearance is to screw the adjuster either in or out after the main bolt has been slackened.

Click to expand...

Got it. I lost the original instructions that came with the hemmings units years ago, and no online version to be found. Recently got around to adjusting them again and could not remember if I had to loosen the main bolt, as the collars do rotate once the grub screw is loosened. Was not sure if the same with the Mark III's

L.A.B. said:

JimR said:

If my front adjuster is on the right side, looking front to rear, it would be in the correct position.

Click to expand...

The front adjuster is on the left on the drawing, looking "front to rear", which is the right hand or 'timing side' of the machine as you would sit on it.

Click to expand...

Than my front adjuster is on the wrong side. I assume this accounts for some or all of my problems that I have been experiencing. Thanks much!

Vernier Isolastic Adjusting Screw Location

From reading this thread, it seems that I have the symmetrical vernier adjusters rather than the earlier factory type.
When installing a newer gusseted swingarm and cradle recently, I fitted the rear isolastics (with zero clearance) and tightened the through-bolt finger tight. To facilitate engine fitment, the dampers were not fitted so the cradle could pivot around the through-bolt. The swingarm and cradle had no lateral movement other than isolastic rubber compression. When I fitted the engine to the cradle, the front isolastic (with zero clearance and the adjuster to the left) fitted cleanly into the frame mounts so I only needed to push the isolastic and engine through-bolts easily to complete the assembly.

Misalignment:
One thread mentions a 3/16" (approx. 5mm) offset if the adjuster is installed on the 'wrong' side. From my recent experience, this would have required substantial force to lever the engine and/or cradle across during assembly. From other threads, it seems some people have had great difficulty installing their front isolastic mount. In light of this current thread, I suggest those people now examine their front vernier isolastic for type, offset and fitment and correct if necessary.
Ta.

Note: left or right are per rider position in this post.