Isolastics discovery

Guido · Feb 5, 2012

I have been doing the Kegler mod thing this morning when I discovered this:
First off, I removed the oil tank, battery tray, fender etc. to expose everything for the swing arm mod. Thats when I noticed this.

As the bike was resting on the center stand the collers for the iso shims were misaligned.

When I have the bike supported under the frame it goes back to the original position.

Since the iso mounting bolt is not cinched tight there is conciderable side play.
I placed my long pry bar under the engine and pry up between the cradle and frame and the whole engine and cradle just moves up and down the distance you see in the pictures.
It doesn't take much effort to move it.

Should it be firm or is this time to replace the rubbers?
I ordered new gaiters and PTFE washers for the rears and fronts.
Is this normal?

Guido · Feb 5, 2012

I also imaging I will need the special tool for installing the rubbers, right?

swooshdave · Feb 5, 2012

Guido said:
I also imaging I will need the special tool for installing the rubbers, right?

Mine went in with the only tool being the one pushing them in. :mrgreen:

Dish soap.

But those look like they are worth pulling out and taking a look at. Just be aware that they may not come easily. Have a new set at the ready.

Does the bike vibrate a lot, you know, for a Norton?

john robert bould · Feb 5, 2012

Yes! the rubbers look shot, and yours look like none adjustable, mayby a change to them?

Guido · Feb 5, 2012

swooshdave said:
Guido said:

I also imaging I will need the special tool for installing the rubbers, right?

Click to expand...

Mine went in with the only tool being the one pushing them in. :mrgreen:

Dish soap.

But those look like they are worth pulling out and taking a look at. Just be aware that they may not come easily. Have a new set at the ready.

Does the bike vibrate a lot, you know, for a Norton?

It is rather smooth past like 2500rpms. Since I don't have a tach cable I am only guessing but at cruising rpm speed it is smooth.
I thought some silicone grease would be used to keep them lubed when all together.

Flo · Feb 5, 2012

If you think about it, rubber gives. Therefore, the weight of the bike on those rubbers will move. So, a bike on a centrestand will probably look like the first photo.
I am thankful I invented a swinging arm mod that can be fitted without removing anything.

Hobot · Feb 5, 2012

I will have to stew on what your geometry load tests imply. Rubbers are likely softened and off set so worth while to remove and reset them in reverse and even add a couple more big cushions back there. Ideal is to spring lift engine so stays about centered. If should be easy to move iso's about 1/4-3/8" as this is the combined motion amounts from both engine hopping on front iso and road loads shoving fr/rr on both iso's at once. Its as much bugger to do mounted in frame as removing power unit to discover other stuff that now at hand vs finding it the hard way and needing to remove power plant. I'm pleased by two Combat's front sets of iso doughtnuts I bench grinder'd a 45' bevel leaving ~1/4" intact flat rim.
Sillycon grease is good practice.

My way to remove and set cushions now after hand working and socket drifting is just lube by power/graphite or soap water and bang the center tube sharp as I can with a wood protective block for 3 lb sledge to strike. BAng mostly all in one swing and fine tune from there.

Guido · Feb 5, 2012

Flo said:
I am thankful I invented a swinging arm mod that can be fitted without removing anything.

Yes, we are too. Thank you, thank you.
Just messin wit ya.
I took all that stuff off to do other things. I'm going to be ripping into the tranny, replacing the horn, which never seemed to work, with one from a Dodge Ram like the one in my truck.
Damn loud horn. Since you can't see the horn anyway, why not.
Primary cover comes off as well because the clutch center needs to be replaced and the gear box sprocket.

Seems like every nut and bolt I remove cost me $50 in new parts. $50 X all the nuts and bolts= lot of bucks.

I wish all I had to do was the swing arm mod.

Guido · Feb 5, 2012

I'll be pulling the cradle I guess.
Steve, you said to stuff extra rubbers in there along with what is required?
There's room for that?
I've never took one apart so this will be fun. (sarcasm)

rvich · Feb 5, 2012

This is like being a judge on X Factor or something. I am going in the opposite direction in that rubbers get hard when they are old and the concensus in the past has been softer rubber is better. So unless they are gone soft is good. The misalignment while on the stand is exactly why you don't adjust your isos while on the center stand. It is also why bikes that have been stored for a long time on the center stand report deformed rubbers.

With that being said, since you are already reporting that you have torn into the bike far enough to get to the horn, you might as well at least pull the rod and have a look at the end rubbers. FWIW, a reputable source says those rubbers should not be sliding around in grease once installed and that they are better off to stick into place. That is why the original recipe was to intall them with gasoline so it would evaporate and leave them in place. The modern alternative is something like P80s "Grip It".

That last statement will undoubtedly draw fire. If the original poster wants to get on here and defend the position they may, otherwise a search on isolastics will find it somewhere.

Russ

Hobot · Feb 5, 2012

Rubbers can decay like people, some harden up while other soften up depending on what they were exposed to. I've found used ones in both states but the hard ones don't allow wiggle ease as soft ones so just assumed what your may be now.

i sliced then peeled off two large doughnuts from old front set and then spread the slice to put them on either inside next to the new outer doughnuts on a supplied iso kit. I figure they are trapped tight as needed by 360' contact with outer iso tube. Could glue me but don't think it matters. With small about useless doughtnuts removed I hear 6 large ones can stuff in to delay the fairly too soon to re-occur sag factor.

Worth while to check flat/squareness of frame tabs and beat file till mostly right. I had to have Trixie's front mount milled back - twice till test fitting allowed mostly hand force to slide in when narrowed below runing clearance.
If ya have front tabs exposed it educational to stick a screw driver in and see what happens on fairly mild levering,ugh. Load corners harsh enough and I think this is the extra torsion spring kick back source that can fish flop off the deck faster than human arms can react to.

DogT · Feb 5, 2012

I've heard some say that silicone makes rubber deteriorate. I haven't a clue, but I used insul-grease on mine which is a silicone based grease for insulating transistor heat sinks. There was some talk about some magic solution that is available on line that is a super slippery lube, forget the name. Heard the gasoline thing too.

My bike was smooth as a baby's butt when I put it away in the late 70's as far as riding. I installed supposedly original (soft) donuts from Old Britts in 08 and it has taken about 500 miles to get the buzz out of the pegs. Seems pretty good at 3K and up, but can tend to put your hands to sleep at 2500. This is with the original 69 setup and .01 clearance for the Isos.

When I pulled out my old donuts, they were pretty oblong, but still soft. I didn't do any comparisons as far as compression and I'm sorry I didn't. I still have them.

I'm sure this doesn't help, but just though I'd throw some more info out.

I didn't need any special tools, I drifted the old stuff out with a socket that fit close and think I pushed them in the same way. Much easier getting them in than out because they were pretty stuck to the cradle tubes.

Dave
69S

Flo · Feb 5, 2012

Spray on chain lube helps the rubbers slide in very easily. Loosely place fully assembled shim carrier, thrust washer & carrier on each end to test for central. It is a quick check.

komet · Feb 5, 2012

Jim Comnoz recommended P-80 Thix for fitting the iso bushes, it's a rubber lubricant that dries afterwards. Go to International Products Corporation and click on free samples. Mine took a week to arrive, USA to NZ; excellent service considering it was Christmas time and sent no charge. Haven't been able to use it yet but specs look good.

Graeme

Guido · Feb 5, 2012

I've been reading some post saying they change out the rubbers only to find it vibrated, something they want to cure or avoid.
I've come this far as far as disassembly goes. I'd hate to button it all back up only to find the vibes from new rubbers are an isolated situation experienced by just a few.
Remember, I am doing the trans work too so it's not just the iso's I am working on so if someone has changed they're rubber out I would like to know how long it took to settle down and smooth out.

DogT · Feb 6, 2012

Well, I've got 500 miles on my new isos and it's a bit better, but I want to get the Hemmings adjusters and see if I can't get the lower speed buzz out of it. After 3K it's fine. I still think the original donuts were softer. I'm thinking it's just a crapshoot what you get, Phil at FairSpares says he sells the original style soft ones. I think the 850s had a harder compound. hobot was talking about drilling holes in the donuts to soften them up, atlanticgreen had a chart of iso distortion as I remember. You might want to compare the old ones to any new ones you get.

Dave
69S

pete.v · Feb 6, 2012

Guido said:
I've been reading some post saying they change out the rubbers only to find it vibrated, something they want to cure or avoid.
I've come this far as far as disassembly goes. I'd hate to button it all back up only to find the vibes from new rubbers are an isolated situation experienced by just a few.
Remember, I am doing the trans work too so it's not just the iso's I am working on so if someone has changed they're rubber out I would like to know how long it took to settle down and smooth out.

My experience is around a 1000 miles. Give or take.

For what it's worth, NOS is not a good option here.

Stillreel · Feb 6, 2012

I've just put the iso assembly on my 71 750 and found the opposite problem. After torquing to 25ft/lbs, there is virtually no gap. 0.001 - 0.002" both front and rear. The bike was literally a basket case and I have yet to fire up the engine (hopefully later this month). But with zero clearance between the collar, cap and PTFE washer, I am anticipating a rough ride. Having said that, my other bike is a 68 Triumph so I well used to vibration.

BC

Matt Spencer · Feb 6, 2012

Very Naughty , ZERO Clearance is a No No . BUT Slackening the bolt as in nipped , for the first ' Ground Runs ' may let it free off / knock the high spots off .

I Consider 5 thou on the wrong side of to much , but 2 a little tight . 2 1/2 to 4 1/2 the set and let to range .2 itll free of smartly , in service.Run In .

PROBABLY youres will free off smartly , BUT , the Idea is ' They Work ' if theres harsh vibes see theyre bunceing at the unit , for the road .
Otherwise remove a thou or two shim . The Frames not up to SOLID Mounted , so some movements essential.That said , If a lever moves it up & down,
like as not its ok .But if ' JAMMED ' at least slack the bolt a notch for start up , please . :mrgreen:

Guido · Feb 8, 2012

I talked to Phil @ Fair Spares and he said that I best leave the rear iso alone. He didn't think the deflection was abnormal and since it doesn't vibrate I should be fine.
One less thing to screw with.
Got all my bits from RGM today and since I tore the primary off to look at the front chain sprocket I noticed it is hooked. Time to replace.
Originally, the bike was a Dunstall with a wide 18" rear wheel, full fairing and clip on set up.
I hated it so years ago I swapped all the Roadster parts from my 73' and put the 74 back to stock.
Now here is my question. The gear box sprocket is a 21 tooth. Is that small for a stock Roadster.
I need to order a new one so if someone knows the stock size, let me know.

Isolastics discovery

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