Isolastic once again.

As you may remember, I overhauled the Isolastic on my Commando many moons ago. It was a very satisfying winter project that - as usual - took way too long even though I could have had it done in under a week if I'd had some free time.

The result was unquestionably a better motorcycle, an improvement measured in megaparsecs, simply put, a proper Commando.

Then Alessio decided to carry out the same upgrade on his Commando, going from the original shim type units, to the vernier adjustable that can be retrofitted to all Commandos.

Seeing as I had already done this on mine, we decided to try this together on his Fastback, which also has a belt drive primary and is therefore an almost identical set-up to mine.

Removing the primary was surprisingly quick and aided by the fact that almost everything that had to come off was barely finger-tight. Good grief!

We found an unacceptable amount of rust in the front mount, and although the rubber itself was showing some wear, I have seen much worse. The front mount itself came off the bike with no resistance, probably because Alessio's crankcases are the original ones and in all likelihood a hair narrower than mine (which are a contemporary reproduction).

A hydraulic press sure comes in handy for this (but isn't strictly necessary):

This particular bike is gradually returning to a "close to stock" look, and in that effort Alessio will be refitting the rear chain guard; to do that, he needs to go back to a 520 chain, and while we had the gearbox sprocket within reach, we replaced it with a new one (still 20 tooth). Again, the mainshaft nut came off with very little effort (i.e. worryingly it was barely more than finger tight).

Everything there is now back on, tight and properly secured.
Moving onto the rear mount, this is where things get trickier, and with one substantial difference from my Commando: Alessio's bike is a 1970 model, which means the center stand is mounted to the main frame, as opposed to the gearbox cradle as it is on mine.

Aside from the fact that he has actually removed the center stand altogether (you rebel, you!), we still need to consider a different way to support the engine-gearbox-swingarm-wheel as we separate that sub-assembly from the mainframe.

The exhausts being tied to both, we unbolted the Z-plates to let them move without the risk of damaging anything (or making things harder for ourselves).

The head-steady on this bike is the original type, made up of the same rubber mountings used for the silencers, as opposed to the actual Isolastic upgrade that's fitted on my Fastback. This too was unbolted to allow extra room to move, as were the ignition coils, rear mudguard, oil tank (actually removed), air filter, battery tray and rear shock absorbers. Yes, that is a lot of stuff, but the alternative would have been to remove the engine altogether and there was no way we were going to do that.

Because of the different position of the bracing tube on the 1970 frame, the operation to get at the rear Isolastic mounting was significantly trickier and harder than on my (1971) machine. This is something I was not expecting, although with some effort (see long list above) we managed to get it done.

Above: finally able to get at the rear mounting (only just), Alessio scrubs it clean of old rubber particles that were stuck on. The rubber mountings themselves were showing signs of compression (the metal tube being way off-center) and were probably not able to provide much in the way of cushioning anymore.

Below: the new unit in place (minus the dust cover).

The front Isolastic gets replaced on the bench and is obviously a much easier thing to do.

Meanwhile, these two keep guard on the shed:

Ferocious.
The grey one is (kind of) a Manx cat. He lost his tail in an accident but he has a good life nonetheless:

We can now begin to realign the mainframe and sub-assembly, bolting the front unit back on, the Z-plates with spacers, nuts, bolts and washers all accounted for, and finally the long mounting bolt/stud that links the whole motorcycle together.

Everything else that has had to come off or moved out of place goes back to its rightful place aboard the machine, ready to ride again at top speed. Fun fact: Norton Commandos are known to set off nearby seismometers due to the huge amounts of torque they unleash on the ground; however, thanks to the Isolastic system, the rider is unaware of the tectonic shift going on underneath the bike, and can concentrate on chasing the vanishing point to the next bend.

This was a good opportunity to give the clutch plates and basket a good clean; outside and in the winter sun:

Most of the plates were stuck together, the basket was predictably dirty (gearbox oil) and Alessio appears to be missing one friction plate, we'll look into that later on.

Below - Happiness is: wrenching on a motorcycle!

I'm glad we were able to get this done together, in a relatively short time and with no major mishaps.
Alessio now has to find the right setting/adjustment of the new Isolastic to suit his Norton and his riding style (hint: it's called a Fastback), and while adjusting the vernier units is certainly fiddly, it is far, far easier than dealing with shims.

Isolastic - part 3

Having to wait so damn long between each little bit of progress is  disheartening; I could have had this entire upgrade done in under a week if only I had control over my own time, but here we go.

☆☆☆ Adjusting front and rear Isolastic ☆☆☆ 

Whilst all Commando models can be retrofitted with the vernier upgrade, it should be noted that when it comes to adjustment there is a difference in procedure between pre-'71 and later variants: pre-'71 models have the centerstand mounted to the main frame, whereas in '71-on models it is bolted to the gearbox cradle.

When you adjust the Isolastic, you have to make sure the sub-assembly is not "under load", so if you have a pre-'71 you can support the bike on the centerstand, however if you have a '71-on you need to retract the centerstand and support the bike with a jack, on the lower main frame rails:

It's commonly mentioned that to measure the clearance of the front and rear units you should shift the engine to one side, so that all of the "gap" is on one side of the engine and you can get a more accurate reading, but I prefer to not put any stress or load on the sub-assembly, and measure the gap on both sides instead. It's probably not as accurate, but much easier to do.

The adjuster for the front Isolastic is located on the right side (starboard) of the bike; the adjuster for the rear Isolastic is located on the left side (port) of the bike. The reason for having the adjusters on opposite sides is that it helps center the sub-assembly in the frame - at least it seems so to me: when you turn the adjuster, you're essentially working against the frame so doing this from both sides (front and rear) seems like the right thing to do.

Yes, it's all a bit fiddly with the rubber gaiters, but absolutely doable; there is easy enough access to check both sides with feeler gauges, front and rear. With the through-bolt torqued to 30lbs./ft, I started from virtually no clearance on the left and on the right. To adjust the gap you slacken the through-bolt, turn the adjuster using the tommy bar that comes with the kit, re-torque and measure again. This will take a few attempts to understand how much of a turn corresponds to how much of a change in the gap; and anyway the ultimate test is riding the bike where and how you want, and noticing how it feels. Then take it from there.

In the end I settled for 0.25mm (or just under 10 thou) at the front and rear.

☆☆☆ Fixing the head steady ☆☆☆

As far as I know, the Commando was always meant to be put into production with three vernier adjustable Isolastics, but time and money constraints meant that the factory had to do the best it possibly could (I won't say "cut corners" because that's unfair), hence shims instead of the vernier adjusters, and simple rubber mountings for the head steady.

An actual Isolastic head steady became available later on, for the production racers, and was eventually manufactured and sold by the usual suspects; it has been a very common upgrade for many people, and one I would recommend.

Truth be told, I made a mistake when originally fitting the Norvil head steady years ago, in that I did not shim it at all, I just bolted everything up and left it at that. That of course was a mistake, and there was no way this could have worked properly if fitted improperly!

After all, we have the same exact one on the Interstate and it works well there, which is what made me think there must have been something wrong with mine as opposed to something wrong with the head steady's design, which is actually quite good!

So, the first thing was to remove the outer plates and clean up the rubber bushings' housing, as well as the end caps (or shim cups, whatever you wanna call them). This is when I noticed the first, glaringly obvious problem: the shim cups had not been machined properly and did not fit over the main body of the head steady; instead, they were just partly pressed on but not at all square with the outer plates, in other words there was no way this could work. I spent some time taking measurements and filing away at the shim cups until I got a proper fit, so that's one thing done.

I have new rubber bushes that I bought from Andover Norton and will probably replace these as well at some point. For now the existing ones are fine, and I also want to try making some sort of comparison between just the old and new Isolastic (meaning the front and rear mounts).

I then replaced the PTFE washers with new ones, and discovered that I had assembled the whole thing so poorly (years ago) that one of the washers was all torn to bits. Mea culpa!
After that it was "just" a matter of trying different shim thicknesses to get to a supposed ideal clearance (at the moment it's just over 10 thou). It took about four attempts, which means assembling and torquing everything each time. This is time-consuming and fiddly more than anything, but access is easy; shimming the rear Isolastic (the one above the gearbox) on the other hand must be some form of punishment in Tartarus, where Commando owners who neglect their machines are sent to shim and reassemble the whole engine-transmission-swingarm-wheel, only to find that the clearance is always wrong and having to start over, for all eternity.

As I mentioned earlier, tightening fasteners to the correct torque is very important; this is not only so the system can work as it was designed to, but also so that in between various attempts at shimming to the correct clearance, you can have a fixed point of reference when checking with feeler gauges.

☆☆☆ Test ride and verdict ☆☆☆ 

Test ride indicated expected performance of critical vehicle systems. A less dry way of saying that is "WOW this bike has never run so well!"

Time to see if all I've done is worth a damn: as I wheel the Fastback off the lift and onto the driveway, I don't hear any squeaks, rattles, clangs or any other unacceptable noises... except I can hear the rear chain rubbing against the primary chaincase ever so slightly: to be honest I don't think there's much I can do about it (without removing the chaincase again, which ain't gonna happen), so I might just wait for the chain to "find its place" after a few miles. I'll keep an eye on it.

It fires up easily enough and I take a moment to let it warm up, while checking that nothing is falling off (you never know!)

It had occurred to me that it would be prudent to check the primary and clutch at idle (with the cover off obviously), but at least from appearance it all seemed to work fine. That said, I noticed something of a wobble at the clutch that had me a bit worried at first; on closer inspection however, the clutch basket is running nice and straight and what I saw was actually the diaphragm spring slightly off-center. I could try to re-assemble it (again) to remedy this but I suspect it's not a big deal.

When you disengage the clutch with the roller needle conversion, you get this extremely satisfying little chirp, followed by a Ducati-like chatter of the clutch plates, very audible with the cover off. The point of this conversion is to give lighter clutch action, less drag, a more square lift on the diaphragm spring, but most of all it is to annoy your friends when you brag about it, which is priceless.

Engaging first gear is not as smooth as it should be, I think it's to do with the rearset linkage more than anything else, and only something I notice from idle, otherwise the gearbox is perfect as always. I can try adjusting the linkage itself but it's never going to be as refined as the original footrest/lever set up.

As I mentioned before, clutch action is light, quick and smooth, no complaints there.

The bike feels firm, taut, lean and light-footed; overall there's an immediately appreciable difference with how it was before.

There are two things I want to focus on here as I accelerate and use the gearbox along the typical twisty country lane, that is to say the Isolastic, obviously, but also how the new sprocket works: what I mean by that is whether or not the lower ratio lets me be "on the cam" sooner and longer.

Trying to separate the two things and rationally making mental notes, while the bike is running so well  and is such ridiculous fun is actually difficult and a bit strange, and also the point is that it all works together to deliver such a fantastic ride, that that's the indicator I should really be focusing on!

So, as strictly related to the new gearbox sprocket, comparing it with the previous 21-tooth item, this now feels "quicker" for lack of a better term, and it definitely unlocks the 4s camshaft much sooner and much more easily than before. Exiting a corner I twist the throttle as I normally do, but now acceleration is definitely different, and it has changed to be a little bit nasty; I think to myself "hey... where did you come from?" as the needle on the rev counter hits 5.000 and the bike rights itself with a little flick of the front end, then levels out pointing straight at the following corner.

Moving on to perceptible vibration through the rev-range, I am relieved and enthusiastic to report that the Isolastic upgrade works.

I'm in second gear approaching an indicated 2.800 rpm when suddenly, there it is, the magic switch: there is no change whatsoever in the exhaust note, no drop in acceleration or upset in handling. Rather, the very physical perception of vibration disappears and is replaced by a sensation of riding on air, as Peter Inchley said:

The Commando is smooth as a magic carpet and just as fast.

I wonder what the Norton development team must have felt like when they tested the Commando for the first time and were the first to experience the Isolastic; that must have been a good day at the office, for sure.

Just thinking about the handling now, it is so smooth, there is a familiar feeling of unending torque and constant acceleration, but finally unmarred by vibration; the term "GlideRide" immediately comes to mind. Power delivery is now absolutely effortless as the machine glides over the road enveloped by a soundtrack that is equally smooth and full-bodied. Wow, wow, wow, what a bike!!

"Suddenly we've started a revolution on two wheels - It's called the COMMANDO 750. Inclined engine, better cooling. GlideRide frame—goodbye vibration" - Motor Cycle News 1968

Since 2013 I have been much more involved in the maintenance of this motorcycle, personally taking care of most tasks except for those that require specialist equipment or skill beyond my own (e.g. when I sent the cylinder head to SRM to be refurbished). Since then, I have gradually and significantly improved the Fastback's overall performance: you mustn't take this to mean solely speed, but also reliability, ease of use, handling and things of this nature.

Already a couple of years ago, I got it to the point where the bike was very much in a sweet spot, and have continued to improve it with things like a clutch overhaul, different tires, new exhaust silencers, etc.

Every step has brought me closer to that WOW moment I mentioned above, and now with the 20-tooth sprocket, and with the upgraded and properly adjusted Isolastic, this motorcycle is an absolute dream to ride.

Simply put, the Fastback has never run so well in the fourteen years I've owned it; I couldn't be happier.

This process of constant improvement, with discernible steps and stages, closely mirrors the path of liberation from karmic matter as understood in Jainism. It's obviously an oversimplification, but the moment I decided I was going to take over the maintenance can be equated to the point where one stops the influence of karma, with every subsequent improvement as a way to gradually shed said karma until the attainment of Moksha, i.e. a properly sorted out motorcycle.

Once you've wrapped your head around that we'll then expand on what motorcycles actually are... but I'll leave that for another day.

The little snippet below from a now old copy of Classic Bike sums up perfectly what this motorcycle feels like to ride:

Test complete.

☆☆☆ Assorted musings ☆☆☆

The workshop manual specifies an ideal clearance of between 0.006″ (0.15mm) and 0.010″ (0.25mm) but there is something to be said for a "trial and error" approach, especially after a rebuild. Just as for clutch stack height, in the end what works best for you may not be exactly what is specified in the manual. I may well end up revisiting the adjustment on mine after I've had a chance to take it on a proper ride.

Check the clearance by placing the feeler gauge between the PTFE washer and the shim cup.

Set the clearance for the front and rear units first, then move on to the head steady.

At the moment I'm at about 0.010″ front and rear, and just over 0.010″ for the head steady. This seems mostly just right, but I think I noticed some vibration creeping in around the 5.000rpm mark during the test ride, so I may try some further adjustment to see if I can iron this out.

Besides from setting the correct clearance (whether it be with shims or vernier adjusters) another thing that is very important is the torque setting for the various retaining bolts. You must get this right, or the whole system just isn't going to work. Also, checking and adjusting as needed may be something to add to a yearly service.

Torque the Isolastic locknuts to 4.15Kg-m (30lbs./ft) for the front and rear units, and to 3.4Kg-m (25lbs./ft) for the head steady.

If clearances and torque settings are all correct but the Isolastic still won't kick in when the engine is around 2.500/3.000 rpm, check for something in the rubber mounted sub-assembly (engine-gearbox-swingarm-wheel) touching something not rubber mounted (e.g. main frame, Z-plates, side stand).

Related to the point above, you should always keep in mind that, when fitted on a Commando, rearsets introduce a problem that's hard to circumvent: the gearshift linkage effectively connects the mainframe to the sub-assembly, but without any sort of rubber mounting, cushioning or other flexibility built in. This creates a point where vibration is transmitted and can negatively affect the effectiveness of the Isolastic.
By contrast, the original set up has the gear lever bolted exclusively to the gearbox, while the footrest is bolted to the Z-plate and there is nothing connecting the two, other than your right foot.

Seeing as I run a belt drive conversion, is this now a beltcase rather than a chaincase? Ah, the laughter.

You may have noticed in some of the photos that bits of the frame look like they could use a touch-up or even a full on paint strip and re-spray. I want to address the lower yoke, which is not looking good, but other than that I'll leave things as they are and the reason for that is that 'done' is better than 'perfect'.

An Aladdin blue flame kerosene heater is of course the only appropriate means of heating the shed when working on a British motorcycle (a cast iron wood-burning stove would otherwise be acceptable for a Harley-Davidson or other machines).

Isolastic - part 2

At long last, I was finally able to get back to this and make some progress.

Oh, hello gearbox sprocket, my what big teeth you have... 21 to be exact. Hmm...

Yes, I know the sprocket has nothing to do with the Isolastic, but this was the typical "while you're at it" scenario, and I've been meaning to improve the gearing on my bike for a while now. More often than not, that would mean fitting a larger sprocket, but this time we're going for a smaller one.

First, the small retaining screw comes off, then the locking plate.

After that, the mainshaft must be prevented from turning in order to loosen the left-hand thread nut (in the photo above, on the right); I ended up doing this by placing two wooden chocks under the wheels and tying heavy duty straps from the frame to the lift, otherwise if you're working with just the gearbox on a bench you can use a length of chain locked in a vise. Andover Norton also sell a nifty tool to help you do this.

The retaining nut measures a whopping 1½″ across the flats (AF) or about 37.5mm. Because the mainshaft is in the way, a conventional socket just won't work, and even a deep well type may not be enough to reach. You need a tube wrench, but then the issue becomes finding a tommy bar that will hold up to the torque needed to undo the nut...

I ended up using the thumb and index finger of my left hand... because, shockingly, the nut was completely loose. I find this alarming and I've been wondering how this could be, so I've thought about it a bit and this is what I reckon:
1) the nut cannot come off if the locking plate is on; that, it was, and the securing screw was nice and tight.
2) I dug around my archive of photos taken during the rebuild many years ago, and found that I must have installed the sprocket, locking plate and screw, before handing the bike over to someone else who then finished the primary and other things for me.
3) What I think happened is that, at the time, I fitted the sprocket but didn't have the right wrench to properly tighten it (and the rear chain wasn't on, so I couldn't lock the wheel either), so I must have thought "I'll do this later" and then forgot.
Obviously this is a big deal and something like this should not just go overlooked. In those heady days there was a lot of activity but also long delays in getting from one stage to the next, so this must have been one of those things that fell between the cracks.
On the plus side, it has never been a problem and there is no damage to be seen anywhere, so all in all this was not as bad as it could have been.

The new sprocket was a nice snug fit on the mainshaft, I drove it in place using a large aluminum pipe. It can be tricky to lock the rear wheel in place, but you have to tighten the nut enough to align the lockring with the hole in the sprocket itself, for the securing screw.

Here's a very large spanner (thanks dad) that was perfect to get this done - remember this is a left-hand thread nut.:

Ah, one of the most reassuring sentences in the English language...

I used a new screw with just a drop of thread-lock.

One tooth may not seem like much but it was enough that I had to remove one link from the chain for a proper fit.
This is now done and I can move on to...

☆☆☆ Refitting the primary drive ☆☆☆

First things first: the crankcase has to be clean and free of any bits of old gasket or sealant:

I thought this would be an ideal opportunity to check all the various fasteners in the sub-assembly, that is to say the through-bolts that secure the engine and gearbox in their cradles. Shockingly, they were all loose, at least two of which dangerously so. I tightened everything down as it should be and I reckon that between the new Isolastic kit and this important bit of maintenance (for sure to be added to the yearly service before the riding season gets under way), this motorcycle should show a noticeable improvement in terms of handling and vibration.

I have high expectations from this upgrade, perhaps I shouldn't but I really want this to turn out well. 

At this point, if you're undertaking a complete rebuild of the bike from scratch, you ought to check that the crankshaft and mainshaft are in alignment (i.e. actually parallel to each other). In this case, I hope I'll get away with having refit everything as it was, seeing as I didn't disturb anything other than the primary chaincase during disassembly, and didn't move the gearbox at all. It looks ok, I'll find out for sure when I actually get to ride this thing.

New sealant goes on, then the new gasket and then the inner primary cover.

Alessio had noticed a big ugly hole in the inner chaincase and was wondering what the hell had happened; this was back when I had to replace an engine mounting bolt but didn't want to dismantle all of the primary chaincase, and obviously something I was only able to get away with because I run a dry belt drive with no oil. I tidied it up with a reamer and sealed it with a rubber plug; much neater now.

There are three retaining bolts with locking tabs that secure the inner chaincase to the crankcase - it's worth taking your time and doing this very carefully and being as gentle as possible: a mistake here could be bad news as you're threading directly into the crankcase.

The locking tabs come already pre-bent to help you during final fit; neat!

The front pulley, rotor and stator go back on without a hitch, I just replaced the woodruff key for the rotor with a new one, as the old one was showing some signs of wear.

Before reinstalling the belt, I cleaned it and inspected every tooth looking for tears or damage: all looks well. The clutch basket also got a good clean and I put everything back in place, with a new tab washer for the center nut.

I faffed around with the clutch pushrod way longer than I should have (I've fitted the RGM needle roller conversion, which is cool and all, but is a bit of a pain to set up) and finally refit the diaphragm spring and gigantic circlip, then, at last, the outer case. Done.

Oh except that now I have to actually dial in the vernier adjusters; so join me again next month (at this rate!) when I go over the front and rear Isolastic units, then the head steady.

In closing, a word of gratitude and appreciation for the late Bob Trigg, who passed away recently and whom every Commando owner will always thank for his brilliant contribution to this fantastic motorcycle.

Isolastic

Rivers of ink have flowed for half a century (not to mention the countless bytes within the virtual world) to describe the Norton Commando and its revolutionary Isolastic system, arguably mankind's greatest achievement of all time.
I would hazard that any article written about this bike mentions it at least in passing, often flirting dangerously with plagiarism of what's come before...

So, since you already know all there is to know about the Isolastic, I will instead tell you about my machine.

As you may know, I got this bike as a... well, the word that actually best describes the state it was in, is the French épave.

The restoration effort we undertook was very thorough and not without its hurdles, however the result was well worth it. At some point with these endeavors you can reasonably claim to be finished with the restoration, and begin actually using the damn thing in the real world.

This is where we enter a much more subtle realm, that of maintenance and improvement: since the whole thing actually works, it becomes easier to isolate (no pun intended) those areas that can be improved, and it's usually possible to be far more surgical and focused. This is where my motorcycle has been for a good while now, and whenever I do bring it in for maintenance, it is for very specific and relatively easy things.

There is a vast repository of knowledge available when it comes to the Norton Commando, and most problems have already been encountered and solved by someone else, so you're hardly ever in uncharted territory.

Of all the things that have been said of the Isolastic, in my opinion two in particular really capture the feeling of a properly set up system: it has been described as a "magic switch" (source unknown, but a common enough idiom among Commando owners) and as "floating drive" in Cycle magazine's September 1969 test of the 750 'S'.

There is a point in the rev range, usually when hitting 3.000rpm, where all perceptible vibration simply vanishes. What's important is that this is not a progressive, gradual thing; it is a sudden (but predictable) on/off magic switch, unmistakable and impossible to ignore, it just never goes unnoticed by the rider. The next thing you immediately realize is that no other motorcycle in the world behaves this way, and by the time you're done thinking that, you're usually tearing through the gears and accelerating hard, surfing a tidal wave of torque and horsepower that is, in a word, addictive.

That surge is entirely down to the Isolastic being in perfect shape, otherwise the ride will be mediocre at best, and downright dangerous if not addressed quickly.

During my rebuild I decided to fit the vernier upgrade, as I didn't want to faff around with shims, especially for the rear unit which is harder to service. It seemed like a good idea at the time...

What I didn't know, was that the kit I ended up fitting was a poorly made reproduction using a very hard rubber compound, and just bad engineering at its core. Repeated attempts at setting the right clearance never seemed to produce much of a difference, and I feel it is now time to get back in there and sort this out once and for all.

☆☆☆ Disassembly ☆☆☆

The first thing to do is to study the original Norton Workshop Manual thoroughly, and then peruse the excellent accessnorton forum if there's anything that's not quite clear.

Overhauling the Isolastic (plus a little extra, bonus task while you're at it - more on that soon) is a fairly big job in terms of the amount of stuff that needs to come off the machine; you also need a couple of special tools and pullers, possibly an air/impact wrench or a very long breaker bar.
That said, it is absolutely doable for the home mechanic.

Let's get started!

Because the Commando is essentially made up of the main frame and the powertrain sub-assembly, you need to support both independently at different times. You can do this with a jack underneath the lower cradle tubes of the main frame, and the centerstand which is bolted to the gearbox cradle on '71-on machines. You may need another jack to support the front of the crankcase when the front Isolastic mount is removed.

The primary drive has to come off, no point dancing around this. Get stuck in there and remove the crankshaft nut, remove the stator and rotor, then dismantle the clutch and pull the whole basket off.

Yes, it's a wee little breaker bar and it worked a treat. After all, as Archimedes famously said "Give me a lever and a place to stand and I shall remove the crankshaft nut."

The tinfoil was a precaution in case there was any oil, but since none seemed to have seeped past the crankshaft seal, I will use it to make a hat, as the one I'm currently wearing is a bit tattered.

Needless to say, keep all the parts neatly stored in clean containers, don't lose anything and pay attention to woodruff keys and various shims and spacers throughout. I won't get too specific here because if you're thinking of doing this on your Commando you really need to read the workshop manual.

Once the alternator and the actual primary drive have been removed, all that's left is the three retaining bolts around the crankshaft: these are threaded directly into the crankcase, so take a moment to control your breathing, visualize the parts moving as you undo them, and treat everything with respect. Gentle hands, ok?

And that's it, that's the primary chaincase removed, easy, right? Actually, provided you have all the tools available and you know what you're doing, getting to this point is lightning quick; LIGHTNING QUICK, you guys.

Some of these parts look a bit dirty, I'm going to give everything a thorough clean and it's going to look like new in here when it's all back together.

If removing the primary drive is a relative breeze, what follows is a descent into madness, as you remove more and more parts from the motorcycle (gas tank, complete exhaust system, at least one Z-plate and both side panels) and a balancing act worthy of a Chinese acrobat as you lift and move the powertrain and the frame, then the frame and the powertain, up and down, back and forth, sideways and oh crap it's gonna fall! Have someone there to help you. Thank you dad.

We can now remove the front engine mount. You'll also note that the head steady and the air filter will come off to gain some wiggle room.

There's nothing else left to remove around here, so it's time to stop procrastinating, bite the bullet and get stuck in with the rear mount.

The rear Isolastic housing is now visible but still not fully accessible, so we have to either lower the sub-assembly in the main frame, or lift the main frame off the sub-assembly. Oh, and the rear shock absorbers may need to come off for this part, just to keep things interesting.

Once the old Isolastic rubbers are removed by whichever method you see fit, it's important to clean the housings and use a lubricant that will not damage the rubbers: this is crucial or your nifty new kit will perish within a short time and you'll have to start all over.

In my case I first lifted the front engine mount out of place (not without difficulty I must add) and clamped it in a soft jaw vice, then bashed the crap out of it to get the old kit out.

For the rear, since the gearbox cradle stays where it is, I rigged up a puller using part of the clutch tool and some bits of rubber to protect the frame. Surprisingly, it worked well:

☆☆☆ Defects of my kit - comparison with Andover Norton parts ☆☆☆ 

I now want to bring your attention (if you're still reading, that is) to a comparison between the badly made kit and the proper new one by Andover Norton.

You can see that the old kit's metal tubes are far too big for the bolts, and only held by two abutment pieces, but only one at the front/left and one at the rear/right... not even one on each side for each mount! Supposedly, the torque setting would bring the whole thing in alignment and somehow work... This is just complete lunacy and it clearly cannot work.

To confirm my suspicion, I then found this: https://www.accessnorton.com/NortonCommando/isolastic-conversion-kit.5053/

The metal tube itself is shocking, it's a crappy seamed pipe that I wouldn't use for a toilet roll hanger.

By contrast, the one in the Andover Norton kit is fully machined and a proper fit for the retaining bolt:

Another glaring difference, and perhaps the most important, is the hardness of the rubber compound:
The inferior quality kit is definitely harder and even the shape of the rubber bushes, and the overall finish is just off.
Andover Norton's is soft and squishy at the front, a little firmer at the rear.

☆☆☆ Reassembly  ☆☆☆

I started by fitting the new rear unit, it is obviously a tight fit and you have to compress the rubber to get it started, but with careful use of a flat blade screwdriver, it is possible to guide the first bush into place (this is where some grease is also essential):

Once in place, the end caps, PTFE washers and rubber gaiters go on:

Getting the front Isolastic in the housing is a lot easier:

After installation, it's just a matter of lowering the main frame on the powertrain and bolting them together using just three bolts: front, rear, and head. Although the image below is very familiar to Commando owners, when you see this in the flesh metal it's really striking, to see that this motorcycle has been engineered and built like this, a very gutsy move by the Norton team, and one that will never cease to impress me, and that I'll never cease to praise:

Before bolting too much stuff back on, this is a rare opportunity to give this bike a deep clean, something dad did using a compressor-assisted sprayer with kerosene/gasoline. It's essentially one spark away from being a flamethrower, ok?

The next phase will be refitting the primary drive, actually adjusting the Isolastic, then refitting exhausts and bodywork; that may have to wait until February (!) but this post will surely keep you busy until then...