Updating / Replacing Isolastic Mounts

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As for vernier kits, I wonder if somebody is going to carry on with the Mick Hemmings kits? I notice that Andover-Norton has a pre-Mk3 vernier kit available. Anybody have experience with it?

https://andover-norton.co.uk/en/shop-details/17047

Anybody have contact with Mick or Angie? Do they still have some kits on the shelf?
 
Fullauto said:
The CNW headsteady (by Jim Comstock) works very well (over 50,000 miles on mine) whereas I'm led to believe that the DT top mount has a non sealed bearing which can wear out over a relatively few miles. The CNW headsteady is plug and play with no adjustment needed.
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I believe Dave Taylor head steadies from RGM have been updated for that reason.
 
rvich said:
If you don't have a workshop manual, buy one or download a digital one from the tech section here.
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A workshop manual is normally considered as methods expediter for a fully trained mechanic. This, more or less, was printed in the preamble of one manuals I read.
The simple basic information is often very brief. The shop manual is NOT a step by step beginners guide to do rebuilding restoring critical inspections and evaluation. I does help.

Welded 1/4-28 nuts on the rear of the cradle was the cheap fully effective fix... to fix 72 combats where the cradle swing arm pin hole was made sloppy. So norton supposedly made +.002" OS pins for repairs.
It was in the INOA tech digest in 1987.
15 years later before I heard of the Kleger clamps.
 
I have run my DT head steady for over 50,000 miles with no ill effects. I re-lube the joints about twice a season. I use the Mk3 spring type.
Cheers,
 
Last year I replaced my original front iso's on my 850 with the heavy duty ones form RGM. The originals were almost non existent but no vibes at all. I was disappointed with the result of the H D rubbers, Vibes through the foot pegs till about 55 mph 21 tooth sprocket. Stuff it, I removed the rubbers and trimmed them down to get a loose fit in the tube. Vibes are a lot less now but more than the were before. I will be ordering the softer ones this week to replace the ones in the 750 which are still original but give vibes through the handlebars. I still run shims, but have had special hard with plastic cushion washers. These have been on the bike for about 6 years and I have never had to adjust them from the 5 thou they were set up with originally. I did not change the adjustment when I renewed the rubbers. I also have a Ludwig style head steady. So simple and light. I used an original pair of P T F E front cushions in the head steady mount. A great idea. Both bikes have the same head steady now.
I dont recommend changing the front iso system as it is so easy to remove and adjust if necessary. The rear is a different story but with the hard plastic cushion/spacers, I dont have to be concerned about adjustment.'I think the plastic I used looked the same as Ludwig used in his head steady but cant be certain.

Thanks again Ludwig.

Dereck
 
Appreciate all the thoughts. Definitely not in a hurry. Mine doesn't vibrate much at all versus what I'm hearing. This is primarily a California / Arizona bike so not sure if that matters but it doesn't sound like something to mess with. Perhaps inspect but until it gets bad no reason. It handles fine. I don't have tons of vibration below 3,000 at all.
 
Tornado said:
There was/is an adjustable rear iso option from Mick Hemmings that uses just a cap and the stock multi piece rubber components. This can be installed without removing the rubbers and it runs about $50 I think.
Not if you are converting front to vernier, you need to get the version made to fit the markII frame, otherwise the bracket needs cutting down.
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in Jan 2019 Angela found 2 or 3 set that mick was hoarding, i got one of them. Angela said she still had some end caps for the rear but not the front, best to contact them directly... the machinist was retiring and so their source dried up, but that was a year ago, so best to call them if thats what you want.
 
kerinorton said:
Last year I replaced my original front iso's on my 850 with the heavy duty ones form RGM.
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Sounds heavy duty alright might be suitable for a big interstate gas tank with loaded tanks bag, big guy/heavy rider, long distance rally goer, loaded his commando down with camping gear.

One group rally trip a friends bike broke down and we ended 2 up on my commmando for the parts chase. I was much heavier back then, almost 200lbs, and my friend was probably over 225. I could immediately feel the iso's were compressing to the point the secondary buffers were fully compressed and loaded and it felt like a rigid BSA or Triumph.

GVWR may be 880 lbs for mechanical limitations but, as I describe to folks, a stock commando is better if not used as a pack mule. This also rules out a side car.
 
dynodave said:
Sounds heavy duty alright might be suitable for a big interstate gas tank with loaded tanks bag, big guy/heavy rider, long distance rally goer, loaded his commando down with camping gear.

One group rally trip a friends bike broke down and we ended 2 up on my commmando for the parts chase. I was much heavier back then, almost 200lbs, and my friend was probably over 225. I could immediately feel the iso's were compressing to the point the secondary buffers were fully compressed and loaded and it felt like a rigid BSA or Triumph.

GVWR may be 880 lbs for mechanical limitations but, as I describe to folks, a stock commando is better if not used as a pack mule. This also rules out a side car.
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?
I don't see how the weight of rider and gear can compress the isos.
 
FWIW, the originals on my 74's rear was severely "off-center" although the rubber seemed fine. I did not check the lateral movement prior to R&R. the fronts on the other hand, had (as I remember) about .045" lateral movement. my gaiters were rock hard, brittle, and overall in sad shape. the internal steel bushings were badly rusted, and the LH outer rubber bush was dry rotted. replaced with the kits designed for pre-Mk3 retrofit - AN kits purchased from old britts. seems everything, including new head steady rubbers was around $300. installation, not too bad (and i'm a novice) - no surprises, however my oil tank and battery tray, and most other things were removed and out of the way. I would say, actual (noob) clock time was in the neighborhood of 8 hours (over 2 or 3 days).

on originals and condition - i'm nowhere near an expert on the subject, and this is just my 2-cents and opinion, but I can't believe 45+ year old rubber still has the same "bounce" as new. time, the elements, and the environment takes it's toll on all that rubber stuff. when I disassembled my originals, there was no signs of any kind of lubricant used at the factory - I suspect they may have just used soapy water as an assembly lube. I assembled my new mounts with generous amounts of high-end silicone grease.
 
with the shocks at the angle they are the more weight you add the greater the force is to push the power train to the rear in the isolastics. you could put the shocks at a more vertical angle to counter the effects of more weight.

ludwig said:
?
I don't see how the weight of rider and gear can compress the isos.
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ludwig said:
? I don't see how the weight of rider and gear can compress the isos.
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I'm surprised you make this statement OK if you never thought about a commando's dynamics. I would not expect your question to be as a troll.

The thrust analysis due to load is as follows:
A featherbed rear shock angle is approximately 12 degrees, BSA A-65 approx 18 degrees, commando is approx 30 degrees.

A load on the bike frames, primarily the rear, causes a rearward thrust.
Take your rigid bike. Disconnect the chain and rear brake cable/rod. Remove the rear swing arm bolt/shaft, insert your fingers than drop the bike with an added 500 lbs. Any idea why your fingers were cut off? rearward thrust is the answer.

On a commando the shock absorber rearward thrust load triangles are 3 fold. front iso, rear iso, top iso. Top iso is eliminated with the DT head steady.
the three iso's all contribute to restraining the load from the horizontal thrust from the rear shocks. The thrust will be at a rate of sine 30degree X verticle load. A 500lb load makes 250 lbs rearward thrust. The 3 iso will share in resisting this thrust. The normal frame is the obvious 3rd leg of the triangle.

Rear thrust is always demonstrated on a commando with no engine or tansmission when only the rear iso is supporting the cradle. The rearward thrust on the cradle by the swing arm which is below the iso support makes the front of the cradle push down pivoting around the top rear through bolt.

More weight makes more load therefore more thrust through the ISO's and the rubber will deflect more. see chart in post#6
 
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chart in post#6

https://www.accessnorton.com/NortonCommando/updating-replacing-isolastic-mounts.29872/#post-462936

Updating / Replacing Isolastic Mounts
 
dynodave said:
I'm surprised you make this statement OK if you never thought about a commando's dynamics. I would not expect your question to be as a troll.

The thrust analysis due to load is as follows:
A featherbed rear shock angle is approximately 12 degrees, BSA A-65 approx 18 degrees, commando is approx 30 degrees.

A load on the bike frames, primarily the rear, causes a rearward thrust.
Take your rigid bike. Disconnect the chain and rear brake cable/rod. Remove the rear swing arm bolt/shaft, insert your fingers than drop the bike with an added 500 lbs. Any idea why your fingers were cut off? rearward thrust is the answer.

On a commando the shock absorber rearward thrust load triangles are 3 fold. front iso, rear iso, top iso. Top iso is eliminated with the DT head steady.
the three iso's all contribute to restraining the load from the horizontal thrust from the rear shocks. The thrust will be at a rate of sine 30degree X verticle load. A 500lb load makes 250 lbs rearward thrust. The 3 iso will share in resisting this thrust. The normal frame it the obvious 3rd leg of the triangle.

Rear thrust is always demonstrated on a commando with no engine or tansmission when only the rear iso is supporting the cradle. The rearward thrust on the cradle by the swing arm which is below the iso support makes the front of the cradle push down pivoting around the top rear through bolt.

More weight makes more load therefor more thrust through the ISO's and the rubber will deflect more. see chart in post#6
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bill said:
with the shocks at the angle they are the more weight you add the greater the force is to push the power train to the rear in the isolastics. you could put the shocks at a more vertical angle to counter the effects of more weight.
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I am well aware of that, and Dynodave's explanation is correct for a static bike.
On a moving bike, the forward thrust of the rear wheel ( through the swingarm into the engine cradle ) compensates that rearward thrust in the isos. The heavier the bike, the harder the rear wheel has to push.
I wouldn't be surprised if the 30° angle of the rear shocks is an essential element in the Commando frame design for exactly that reason.
 
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Pretty sure comnoz fiddled with the 30deg & said something positive about less angle, but then went with original.

Also, prob not relevant, but the speed record norton went with an extended swingarm & a very small angle for the shocks.
 
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Loading and thrust are seemingly extreme when thought about...in a engine shaking transmission lump being used to propel the front rolling chassis and attached engine trans rear wheel assembly whether stationary or down the road.
Of course the job of the iso is to decouple the two halves
Commando from static to light cruise iso's are being gently pushed forward and up to propel the bike down the road.

Do a front wheel lifting hole shot and see the additional upward lift/thrust on/through the front iso to raise a good part of 400 lbs toward the sky. I bet the secondary front buffers are well compressed. The engines head steady (if any) has upward movement. The stress on the chain is contained within the trans/rear wheel assembly and I'd guess must have well over 1 thousand pounds of force between the gearbox sprocket pulling on the rear wheel sprocket.
 
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in talks i have had with jim on this he stated he had handling issues with his race bike loading and unloading. he moved the shocks to a lot more vertical position and it was a huge help.

84ok said:
Pretty sure comnoz fiddled with the 30deg & said something positive about less angle, but then went with original.

Also, prob not relevant, but the speed record norton went with an extended swingarm & a very small angle for the shocks.
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the issue is it is defanatley not a one to one ratio.

ludwig said:
I am well aware of that, and Dynodave's explanation is correct for a static bike.
On a moving bike, the forward thrust of the rear wheel ( through the swingarm into the engine cradle ) compensates that rearward thrust in the isos. The heavier the bike, the harder the rear wheel has to push.
I wouldn't be surprised if the 30° angle of the rear shocks is an essential element in the Commando frame design for exactly that reason.
Click to expand...
 
For the OP here regarding your isolastics. You are going to get a lot of advice here, some good, some bad, and that's just from me.

What I think you should do before being concerned about your isolastics is read up on layshaft bearings. Then make plans as to how you are going to verify whether its ever been replaced. If you can't verify that its been changed out since new then you can plan ahead for that project. While you are doing that there will be plenty of opportunity to examine and replace iso's.
 
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