Vernier Isolatic adjustment

I've got my '74 back into one piece with Andover Iso conversion. It wasn't a horrendous job but it sure takes a lot of steps and some bit patience, not having done it before.

Just setting up the clearance. I did the front by levering the engine sideways with a long bar between the frame tube and the engine-case bolt right above the Isolastic. Am I overdoing it? I didn't really crank on it. Just curious about how aggressively one needs to push the engine to the side.

I'd say it set to a tight .010 inch at the front. Going to do the same at the rear.

Do we lube those fancy washers at all?

Thanks for the help.
Mark

Fair breath holding leverage effort w/o any grunt sounds escaping is plenty to get slack out for a measure, which should still be what gap you set on the bench. Air up tires pretty hard to get best sense of isolation and help iso's bed in some hundreds of miles before getting serious about fine tuning unless just enjoy the tedium, which ain't a bad thing in the long run.

O, I am a huge fan of tedium...

Wasn't the same as on the bench after I torqued the big bolt to 25 ft.-lb., so I tediously loosened the big bolt, turned the adjuster, re-torqued the big bolt and measured again and repeated until I got the ten thou.

Ok then hope your tedium tolerance rubs off on me, part of why touch in on basics as need examples for my own encouragement. You got it set to manual starting point, then must ride and diddle ride and diddle until you get sense of best compromise smoothness vs handling tightness. A smooth set set of isolastics still handles like a dream, until really getting wild on sweepers or a flat. Vary air pressure to see that effect on isolation too.

I think this is a Hemmings tome, not sure.

The workshop manual calls for a clearance of 0.010" (0.25mm); for a more comfortable ride you might let this go up to 0.020" (0.50mm) or for better handling at the expense of extra low speed vibration try 0.005" (0.12mm). On any Commando that's been "used" the clearance is often not the same at the front and back or top and bottom of the adjuster, so check all the way around. Remember to push the engine over in the frame away from the side you're checking and torque the mounting bolts to 40lbft. Whatever you do don't over tighten the Isolastics. The frame is not designed for a rigidly mounted engine and it will break. If one Isolastic unit is tight and the other is free then the frame will break very quickly indeed.

For racing, it is possible to tighten the Isolastics so there is effectively no measurable clearance. Do this by adjusting back from a tight setting until the thrust washers can be rotated by pushing them with the end of a screwdriver.

The engine essentially rotates about the rear Isolastic mounting. Consequently, the front unit moves more, wears more and has a greater influence on the transmission of vibration. Any play in the rear mounting is doubled at the rear wheel, play in the front mounting is simply matched in the rear wheel. Therefore it is possible to tolerate more play in the front mounting than the rear and get a more comfortable ride. Try varying the clearances a little and see what suits you best.

Good Luck,
Dave
69S

I find I hit home runs with iso setup when I finish by loosening the 3 bold into the head from the headsteady. Then while sitting on the bike off of the stands, snug up the headsteady bolts. Recheck the isos clearance.

A tight .010 on new stuff should be good.

Thanks for the help. What about some type of lubricant on the PTFE/bronze washers? I wouldn't expect any, but...

Mark

Whitworth Ranch said:

Thanks for the help. What about some type of lubricant on the PTFE/bronze washers? I wouldn't expect any, but...

Mark

Click to expand...

Go down to your local hardware store, go to the plumbing isle and look for "Silicone Faucet Grease".
That was the only place I could find any.
I smear it on all the shims and the PTFE washers.
Of course, I do all my measurements dry before applying the grease.

For those of us without the venier adjustments (such as myself): a 1/4 turn on the ISO mount bolts = approx. 0.015" ??? I'm asking here. Does that sound about right? I can't find the pitch data on these bolts (distance between thread, or one whole turn).

BC

I believe there is a torque setting for the iso bolt. The clearance is specified at that torque setting. Adjusting the clearance with the bolt tightness is not the right way.

Roger that, but when I torque the bolts to the correct setting (25 ft/lbs), there is zero clearance. And I'm certain these machines must not run rigid in the frame. I've use the pitch distance adjustment technique on valve lash adjust quite successfully and so would like to apply the same principles here.

Stillreel said:

For those of us without the venier adjustments (such as myself): a 1/4 turn on the ISO mount bolts = approx. 0.015" ??? I'm asking here. Does that sound about right? I can't find the pitch data on these bolts (distance between thread, or one whole turn).

BC

Click to expand...

No, this is wrong. It's a shim kinda thing. The pitch of the screw may be whatever, but not used when adjusting the clearance.

For those without Vernier Iso, the through bolt has nothing to do with the adjustment. If you have no clearance with the bolts to proper torque, then pull out shims until you do have clearance with the bolts torqued. Adjust as needed. Be sure to have the bike supported on the frame and no the center or side stand.

Do this enough and you will more than likely invest in the Verniers.

Got it. Thanks
BC

Still kinda boggled by iso shims, or, as in the current arrangement, the lack of. I've tightened the front & rear iso bolts to 25 ft/lbs and even with no shims, the is no clearance between the PTFE iso cap and collar. The assemble feels very rigid and will only move with significant effort. Perhaps this is correct or maybe the PTFE washer is too thick? It's my first time assembling this bike so perhaps I'm missing something.

Any thoughts here would be appreciated.

BC

I think you are missing something.
Did you clear all the paint off the ends of the tubes? You might want to relax the headsteady bolt too.

If needed, start re-working the front. It is easy to take it right off the bike and you can set the clearances while mounted in a vise. Once you see where you are at with the front, you can relay this learned info to the back.

A little interesting history to add to the mix:

In the early 90s, while on a ride back home from a Four Corners Norton Rally here in the southwest USA, Brian Tyree of New Mexico was loping along the highway musing about isolastics.

He thought to himself, self couldn't I go home and machine a set of threaded adjustors?

He did so, got a US patent, and went to England to meet with Mick Hemmings to handle the marketing.

Now, I live in Albuquerque along with Brian, and this is the story he told me many years ago.

The first sets of threaded adjusters had a nylon tip on the securing allen bolt, and this could randomly tighten down right on the leading edge of a thread, thus sheering off the nylon, and of course being on the thread's edge have little holding power.

When I talked to Brian about wanting a set back then he told me he did not make them and I would need to order from Hemmings. When i got my set way back then, the isos kept tightening to no clearance because of the above.

I mentioned this to Heinz Kegler and Heinz and I removed my threaded isos and Heinz milled off a couple of unneeded threads, creating a flat spot for the allen bolt to come down on securely. Heinz also felt the holes and the allen bolts were a little too small so he bored out my iso holes and put in larger allens to bear on the newly milled flat spots, thus eliminating the need for the nylon tips. Problem solved, now when set the allen bolts the isos do not move, can't loosen or tighten.

I have no idea if these improvement of Heinz's have been incorporated into the threaded isos you guys are buying nowadays. But if not, that is the solution.

Just a little history for your idle reading!

John Schmidt

For those without Vernier Iso, the through bolt has nothing to do with the adjustment. If you have no clearance with the bolts to proper torque, then pull out shims until you do have clearance with the bolts torqued. Adjust as needed. Be sure to have the bike supported on the frame and no the center or side stand.
Do this enough and you will more than likely invest in the Verniers.

Click to expand...

Amen on above true seasoned wisdom.

The mounting bolts and the long iso bolt torque should have nothing to do with the gap, unless something bent or over size, about un-heard of in Norton-doom huh

The frame tabs can be bent or missmounted some, but very hard to bend square though the frame tubes will twist with just a screw driver leverage in the mount tab hole. This is where I think the slap you down level of hinged handling comes from. Any who you may need to trim one side of the iso rubber tube face so it just slips in between the front tabs with the clearance you want or a bit more so can shim down clearance. Some relieving of the tabs may help too. Realize the chain pulls the front of engine to the LH so iso's tend to wear on front LH and rear RH side skewed, so logical to check those sides for clearance.

I'm pleased with beveling big front doughnuts to 45' bevel till only 1/4" of rim remains in contact for faster progressive isolation onset. You should practice on low aired tires to find out how much your iso gaps can upset you in surprise hinge onset, while going at rates its easy to recover and learn from. Then open or close gaps per vibration protection vs handling security.

You must have on new-ish hi aired tires to really feel what your isolastics are doing as iso's need hard road surface reference to stabilze against. I get full vibrations when catching air time or the second or so it takes for a blow out to fully deflate, so bike ain't being supported by tire till hits the rim, then smooths out again. Harder tires means less vibes but harsher ride, off road at least, sheeze.

As I understand it now, the through bolt tightens against the rubber through tubes and not the cradle or engine mount. As such, when torqued to 25 ft/lbs, the end cap should be free to spin if there were no shims and enough clearance. Shimmed to 0.010 will snug it up to provide the the proper setting.

Sound right?

Wrong! The rubber are mounted onto bushings and the three units are equal to the width of the tube. The shoulder on the end cap and the teflon washers make the adjustable space made proper by the shims.
This is the internals of the front iso. If you just have the rubber stuffed in the tube without the bushing, you might as well go ridged.
I suggest you get that front mount pulled and get some photos online for us to see.

Sorry, that's what I meant. The rubbers mounted onto bushings arranged onto the through bolt. But thanks for the comments and image. Its a great help. I'll get in there again tomorrow and get some accurate measurements.

BC