When to replace an Isolastic suspension

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Joe Schlaberdowski

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I to my first long ride today. There was a bit of buzzing in the grips. I wondered when do you know when you should replace the rubber inserts on the Isolastic suspension?
 
If you look at the position of the end cap compared to the end of the tube and see that the it is way off center then you should replace them. Otherwise replacing them may result in more vibration.

Normal resaon for extra vibration is iso's that are adjusted too tight or a headsteady that is off center and binding the lower mounts. Or carb balance will do it too.
 
no expert, but my thought process was the age of the components. I decided at 45 years old, time and the environment had taken it's toll on the those rubber bushings. my front gaiters were in sad shape and when I tore down the mounts, the rear iso's were severely off center, and the left front bushing was actually dry rotted. didn't check the original lateral side play of the mounts in the rear, but in the front, I had .045". replaced front and rear with AN Mk3 vernier upgrade kits. set the clearance at .010". no experience on any vibration before replacement since my 74 Mk2 was DOA when I bought it. we'll see how things are in a couple months. ;)
 
Just did front on my '74..... Vibes were getting out of hand & when I looked down and saw the tube jiggling about I figured it was due. Rot & wear had taken a toll and done them in over the years. The Vernier mounts are money wisely spent.
 
FYI , My front MK3 ones were toast after 60k miles ,but they are easily replaced. I replaced my pita rear ones later but they were actually in real nice shape , and I am wondering if I should left them as the new rear rubbers seem to be giving me more vibration.( common problem with replacements rubbers) My low mileage 68 and 74 are real smooth and have their original shimmed rubbers.
 
jimbo said:
FYI , My front MK3 ones were toast after 60k miles ,but they are easily replaced. I replaced my pita rear ones later but they were actually in real nice shape , and I am wondering if I should left them as the new rear rubbers seem to be giving me more vibration.( common problem with replacements rubbers) My low mileage 68 and 74 are real smooth and have their original shimmed rubbers.
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I had the same experience, replaced the iso rubbers, the front ones looked like crap, and the rear ones did not show any sign of wear, I replaced both, but unfortunately the thing vibrated more than ever before, I was told that the vibs would "smooth out" over time, but unfortunately it did not.
 
I replaced mine a couple years ago with the CNW kit. Lovely. Lo vibes.

This is the old. Glad I did.

When to replace an Isolastic suspension
 
Buzzing in the grips can be caused by a dry stiff or worn out drive chain.
 
All the above may be true but I find the new rubbers are less compliant than the old. Now who exactly made them and when matter Im sure. How tight they are matters. Does your frame have any alignment problems?
My original mounts were definitely smoother than the current ones. Also notice that you have to be over 3K to get satisfaction. At
highway speeds they are fine.
 
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2.8-3k and my old ones (no idea when and if they have been changed) smooth out, less than this and she's a bit vibey
 
My new ones have what I consider normal vibration at 2400-2800, and it really clears away approaching 3000 to become very smooth. The bike is then running as it did when I first bought it years ago, so I've got no complaints.
 
The best rubbers I've run were genuine AN and for the 70 model. You could stand back and watch the engine happily hop up and down. Go for a drive and she smoothed out like glass over say 2700 R.P.M. They were soft.
 
Many years ago. The 70 has been sold for 5 years now. Blew the money in Bali on massages and Bintang beers.
 
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Ah yes. I sold my 72 eons ago as well. Blew the money on an 850. ;-)
 
I changed my early '69 iso's for some AN I got at Old Brits for the 71 model in 2007 or so with the clips and spacers, same layout though. The vibration was more noticeable and to date there's still a small buzz on the pegs and bars. It took maybe 3 months for the front iso's to take a set towards the bottom by at least 1/4" because I took them off, reason forgotten, so I turned them over and in another 3 months they were set towards the bottom again. I did install the spring on the head from my home made head steady and it helped the low rpm vibrations, but that's all. It's my opinion and just that, that the early iso donuts were softer than any new ones you can get. hobot used to experiment with drilling the donuts to soften them up.
 
my original early 68 ,never rebuilt goes dead smooth at about 2500-3000 rpms (btw for sale)
 
The Titanic's original '73 iso's make it a magic carpet ride over 3K rpm, but I have noticed a bit of sideplay, so some shimming may be in order. Has anyone ever tried to mitigate the dreaded rear wheel offset by fiddling with the iso's?
The SS clone has the adjustable Mk III iso's, which I set rather tight for sharper handling.
 
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