Isolastics Mk3 vs Mk2

It is commonly held belief that the vernier adjustment on the Mk3 isolastics is a vast improvement over shimming the earlier style. Setting that aside, is the Mk3 style of isolastic rubber really an improvement over the Mk2 (and earlier) style with the individual bits as opposed to a single bonded unit? Anybody have any kind of real life comparision to validate it as an upgrade?

As I move through the various aspects of my 850 build I am challenging myself to pick and choose options wisely. Failing at that I would at least like to have some reason I can fool myself with. Most notably on this piece the original isolastics had three rubber bushes as opposed to two on the Mk3. Is more rubber better? Or is it another of those things that can only be speculated on with no real evidence to support either.

I should add that I am not the young whip I once was, and the poor thing is gonna have to carry the weight of my experience. I am tending toward the three bushes.

Russ

Rvich after installing nameless vernier kits front and rear I am dealing with enough dsappointment to commit to a teardown this winter . Vibration is through the entire range and am missing the way it was with a glass smoothness past 2700 r.p.m. Changed out the front internals back to stock,no difference so it must be the rear which necessitates teardown. Adjusting makes no difference to the rear. The motor does not hop up and down somewhat like it used to so if you have trepidations pay attention although I'm sure other owners have differing experiences. I have heard talk of drilling a few holes in the rubbers to achieve more softness but need some more info. before I would even attempt this. Plus rubber batches vary and harden differently.I have heard Hemmings adjuster ends allow you to retain the stock internals so you could consider this too . Good luck.

I stuck new MkIII vernier isolastics in my 1972 Combat a couple of years ago and have been generally underwhelmed by them. The bike vibrates, not terribly, but I expected better. I have fiddled around with the gap settings and found that there was little change in the amount of vibration. I have a low mileage 73 850 with its original (I believe) isolastics. It is much.... much smoother than the Combat. I'm not going to mess with them.
Mick

Russ,

My '74 had what I would say were original hardness rubbers, stock shims, etc. You could almost tell the RPM without looking at the tach. At 2,300 and below there was a definite throbbing (for lack of a better word) in the footpeg rubbers. From there up to 3,000 you could really feel it smooth out. It was as smooth as any Commando I've every ridden. Felt as smooth as a 1 liter BMW twin which I also owned at the time, and we rode those all over for miles on end, and never thought about vibration. They were smooth bikes.

My current '72 had shot Isolastics, and was a mess of rust when I got it. I bought a set of "super-soft" Norvil isolastics from Phil Radford at Fair Spares America. They had a personal note from Les Emery on how to set them up in the package, so that's where they came from. You also didn't have to shorten the front mount with this kit, a straight drop-in. The SS isos were advertised as being smoother in the low RPM range, and that's certainly what I found. It's hard to compare the upper RPM smoothness with the '74 - 850 vs 750 and all that, but I don't think the SS have quite the silky smooth feel of my '74 had. Rose colored goggles? Maybe. The '72 is very smooth, and very rideable at upper RPM. And running it down as low as 2,000 is where it's much smoother than the '74 - not a harsh type of vibe, but the footpeg rubber throbbing business. More range of usable RPM at low speeds. Commandos are super strong down there, and I prefer the lower RPM smoothness.

I also fit my MKIII with these SS isos from Phil, and I'm happy with the results on that one. Again, it's not as smooth as I remember my '74 being, and maybe just a little more vibey than the '72. But, different engines, etc. But, and very importantly, nothing on either of these two bikes are anywhere near uncomfortable to ride at higher RPMs, or highway speeds. Compared the the gnashing of a T140, they are both pretty frickin' smooth, and a joy to ride. Gold Wingers may not think they are smooth - you know they don't feel like an electric motor, but when you consider the engine configuration, they certainly are. You'll probably get all kinds of feedback on this, I think a lot of people I know have had a variety of experiences on this subject.

ETA - I've seen no mention of the "super soft" isolastic on either Phil's or Fair Spares web site. That was a term I first saw in the big Norvil display ads in the front of Classic Bike - maybe in the early '90s when I bought these? Don't remember. Maybe they only use the softer rubber on theirs, just never seen it discussed much. I think Dave Comeau had some sort of graph on the various hardness of these rubbers, but I don't remember much about it.

I have vernia type in my two 750's but stayed with the arigoanls in my 850 mk2a as they were in good condition, the 850 is noticeably smoother than either of the 750's,
I have seen a kit that I think came from mick hemmings which replaced just the shim adjustment- converting to vernia but retaining the o.e. rubber isos, appears to be best of both!
Al

I installed the original part number isos on my 69 from Old Britts. Only thing that changed was the new bushings with the circlips. My old setup did not have that. I did have a message from Phil that the original number items are softer, but don't have any scientific methodology to prove anything. Not sure if Phil uses Norvil donuts, the ones I got from Old Britts were Andover. I can say that I get more vibration than my 40 year old worn out, egg shaped donuts and the washers were completely missing (read powder) so the clearance was probably on the order of 0.1". There was a long thread on this maybe a year or 2 ago, but I never got the feeling anything was solved. Lots of discussion on the PTFE washer too.

Maybe if I have a chance this winter I'll take off the front and compare it with my old worn out ones as far as compression anyhow. I still plan on getting Hemmings adjusters but for now settled on .01" on both the front and rear with the old shims. I can say over the summer it seems to be settling down a bit. I don't get the buzz in the pegs any more, but doesn't really smooth out in the bars until past 55 in 4th, maybe around 3.5K, just guessing on the revs. 19 tooth sprocket.

Of course there those that say there should be no vibration over 1K?

Dave
69S

Why do they call these Screw adjustable isolastics "Vernier"? from my engineering background they are more like a micrometer. I'm not convinced the "vernier" isolastics I fitted to the front of my 70 Fastback, left the engine plates in the correct left to right spacing between the frame ears. But then the accuracy of the frame itself is questionable. That is the subject of another thread.

Hey guys, you have started this thread in the nick of time for me, as you may see in other posts, I now have 2 x 73 850 Roadsters and was due to take a good look at my ISO's on both.
Any idea as to the previous thread link that DogT mentioned.?
Like the idea of the MHemmings upgrade end caps using the original ones .
Regards Mike

I too recently converted to vernier isos on my '70 - the original front was missing bits and the rear plastic washers had disintegrated. I was happy with the improvement the verniers provided, but I had been told that the vibes should vanish "like flicking a switch just below 3k" which I found not to be the case. I reset my headsteady and added a bit more clearance to front and rear iso, but to no net improvement. Now I personally don't think the vibes bad, not as good as my TRX, but really not uncomfortable. In fact, quite acceptable. Same chap with the light-switch comment suggested my headsteady would be to blame. I've not ridden another Commando ever, so I have nothing to base a comparison against, but from what I'm reading here, it seems like it's set up as good as it could be.

Try these links for a start

iso-adjustable-non-adj-hemmings-t8055.html
isolastic-friction-washer-preference-t7757.html
engine-mounting-shim-t4998.html
hard-soft-isolastic-rubber-t4984.html

I'm not sure you will come away with any solid conclusions, I never did, but since I went with the original donuts and bushings, I'm going to use the Hemmings adjuster (vernier, micrometer, whatever, I prefer adjuster) since I don't have to do any machining and can use most of my old equipment. I think the Norvil, (GP), and the MKIII adjusters change your setup, but not necessarily to be machined except for the MKIII on the early bikes. I stand to be corrected. I would love to see a complete breakdown of all these components. It gets real confusing especially for a geezer. That's why I try to stay with original equipment (part numbers).

Dave
69S

If you can still feel a bike running under you after 2500 or so then its not really a fully fettered Commando. Also if you do not have brand new properly aired and fr/rr balanced aired to boot then you can not say anything definitive about why you feel a Cdo running under you with just a logo on the side telling ya it a real Commando.
In case I forgot to mention it, one Must Fit Perfect Tires First or end up trying to diddle dial out for them rather than basic engine vibiration.

I can say this because most of this year on 4th rebuild Trixie Combat I felt the proof I didn't have yet have her in velvet luscious matured state. I did my best learned on Ms Peel's full disapearing act, beveled the front doughnuts 45'ish to 3/8"ish rim left then put in two old large un-beveled doughnuts in the rear "thread adjustable" iso, got the head steady plate bent and bashed and holes expanded to set neutral strain on the Lords rubbers which I also waisted. Didn't Texas trip and back w/o annoyance and was still eager to continue on at the end of 9 hours almost sensation-less bliss. Wore out my old hard tires for two soft newish unused tires to get that ahhh so smooth sense - knowing riders can't get out of their bone and will do & spend what ever it takes for another high like it.

Then can install head and breast links to add another level of secure feeling grace.
The power unit suspension spring is also a good feature for lower nullification.

I remind thee that Norton had to cut the cushions thickness 3 times before they got acceptable nullification. More rubber equals what?

But that's as far as standard wisdom/tradition will take ya, as there's still a sense of a light 450-500 lb bike under ya that's flexy jittery jossltely from wind buffeting the forks and stem and by minor road texture annoyance up reflective marker size, feeding up the pegs and bar grips. No one believes me so far on a very rare modification so no one know's what I'm talking about saying ya don't yet know what's ya'll's missing out on. Planing a smart phone type vibration app to contest Ms Peel with fully loaded GoldWings that just may still transmit theres a busy valve train under ya, pshaw! I know so inconcievable, hehe tat ta.

Turbofan smooth thrust of the hand of God shoving your butt forward into the Future w/o even the sense of flying carpet's ruffles or its fringe in the wind -
just eyeballs and grin getting through.

Steve, throw some pics of you waisted (wasted!!!!) rubbers on here after beveling
Regards Mike

I remember going through this when I was getting stuff together for my rebuild - I'm with Dog T regarding sticking with the original part numbers. I can't vouch for Mk III 850s though.
I'm guessing that the type of headsteady would have an impact on how the motor behaves to some extent.
Mine has the Dave Taylor steady with the Mk III support spring fitted, and with the vernier adjusters set per Mick Hemmings' instructions it's smooth above 2500rpm. I went from a 22T to a 20T gearbox sprocket to make life easier - I was hardly using 4th gear until I swapped.
The real advantage to the vernier adjusters is they can be set by experiment out on the road to get the right combination of smoothness versus tautness of handling. Something I'm planning to do next year.

I found this instructional... shows how much the motor leaps about!

[video]http://www.youtube.com/watch?v=OQGQ8uK-pYM&feature=g-upl&context=G2ce4d7eAUAAAAAAACAA[/video]

Yes , my 750 Mk II spec ' Boinged ' at idle , but other than a chunter at 1800 trundling acceleration , was smooth . though you were aware of a throbbing at 100 knots , steadyy .

The copper impregnated friction washers , didnt like it set past 4 1/2 thou . So didnt .

Obviously chewed out Iso rubbers etc , and it ' might not ' work correctly .

Original blurb on Norvil head steady , stated TWO thou clearance .

The Triangulation and direct location laterally at the top , eliminate movement before it occurs , unlike the squash in the std. rubber top mounts. Alledgedly Theyre Exhaust pipe mounts of of a Mini .
But Cheap .

I don't have pix of the iso doughnuts as all are mounted and uninteresting to view. I just used a bench grinder to bevel the rim down till about half the rubber left to engage on the amount of engine hopping at the front. This action is a pivot on the rear mount so it don't need less rubber but more rubber to help stablize w/o vibes transmitted but still must be set proper gap or vibes. I aslo bench grinder'd a waist in the stubby rubberized mounts both on head steady and the muffler mounts. Engine vibes only move the mounts at most 1/8" either side of neutral, the rest up to 3/8" comes from road thrust loads. Video show the rear tire patch as one end of lever acting on the front iso with rear as pivot. A video of someone tugging side ways on the rear patch reveal the wisdom of Bob Patton's rear link to stiffle the side-side slapping at front into forks that onset hinged affairs.

If beveled bushes improved the vibration dampening, wouldn't this point toward using the Mk3 system with two bushes instead of three in the rear mount?

As a side note. The iso rubbers in my '74 are the original rubber, unless they were swapped out in the first couple years of the bike's life (not likely). To my amazement they look and feel brand new. They are soft, pliable and will bounce back into my hand like a rubber ball when I bounce them off the work bench. I should probably try to get a video of this and post it. I would not have believed this possible prior to tearing down this bike. I think it is probably due to a couple of factors. One, they were not installed with grease but most likely gasoline (as per original instructions) which evaporated off. The only blemish on these rubbers is on the outboard side of one of the rear bushes where something (probably oil from the tank) leaked into the end of the iso tube. The second factor is that the bike sat for a lot of years in a cool climate and probably never experienced anything above 80 degrees and that very rarely. I don't know what else to think.

And yes I am tempted to put them back in service. If nothing else I should get busy and order some new ones to compare the two.

Russ

I have found that the Taylor top steady with Mark III spring type isolastic and SS vernier Mark III isolastics provide the ultimate solution.

The Taylor unit is pre-drilled to accept the Mk III spring kit.

Have the Taylor headsteady with spring in my hand. Awesome stainless quality. Contemplating drilling say 3 holes equidistant into the vernier rear rubbers each setup to achieve more bouncey smoothness,anyone done this ? -or talk me out of it. One more week to go before friends pull/push Crazy up the stairs as a replacement for the Xmas tree. Also fitting the R.G.M. belt kit at same time. Then Mexico to springtime. Merry Xmas to all.

Torontonian said:

Have the Taylor headsteady with spring in my hand. Awesome stainless quality. Contemplating drilling say 3 holes equidistant into the vernier rear rubbers each setup to achieve more bouncey smoothness,anyone done this ? -or talk me out of it. One more week to go before friends pull/push Crazy up the stairs as a replacement for the Xmas tree. Also fitting the R.G.M. belt kit at same time. Then Mexico to springtime. Merry Xmas to all.

Click to expand...

If you haven't run the spring yet, DON'T MESS WITH THE RUBBER ON YOUR NEW ISO SET.

One thing at a time, or you might blame unanticipated results on the wrong thing.

Install and adjust per the instructions, or you might blame unanticipated results on the part(s) instead of the installer and/or person doing the adjustment.

I enjoyed doing this bit of technical measurement (maybe 10 years ago) and was not surprised by the results.
http://atlanticgreen.com/images/frontiso.jpg

I am not in the least interested in "upgrading" :? my iso's to what is being offered today unless they are exacticaly the same as my 72 combat ISO's as shown on the blue line in the chart. Shakes like crazy at idle, but smooth as silk on the road above 1500.