Isolastic adjustment and front to back engine movement?

At anything over idle my bike is smooth as silk but at idle the engine does shake front to back a lot. Been running one of Jim's headsteadies (CNW) for around 5 years & love it. My Isos are on the loose side at about .015 front but .030 in back so I'm going to shim them tomorrow time willing to tighten them up. Never had them apart so can't say what condition the internal rubbers are in. My question is does tightening up the clearance in the Isos do much for front to back movement or is that dependent on the internal rubbers??? Thanks. Glenn T.S.

The gap only matters on how soon isolation onsets and how soon weave/wobble/hinging/horror can onset if pressing turning loads long. The hip hop amount is dependent on how hard/soft the cushions, which can take a set compressed in major oscillation loading so gradually allows more and more of it. They can decay either harder or softer than new depending if oil got into em or not. Ancient Commando owners concluded better to shim both iso's on same side but you will have to shove-lever and observe/measure to decide on ease and trany sprocket to rear sprocket alignment. I prefer more open smoother running gaps over a bit longer-faster stability pressing luck on non-tri-linked Commando. Basic motion is up/dn at front pivoting on rear while parked with some fro/aft shifting added riding from rear thrust and suspension loads.

Hi gtsun.
The rubbers soak up the fore/aft movement. The side iso movement controls the lateral drivetrain movement.
In my experience, a rough guide to knackered iso rubbers is the kick start arm scraping the right header pipe. This resolved when new rubbers were fitted. I recommend vernier adjuster iso's as an upgrade if you are replacing rubbers.
Ta.