Who is Thomas Dunstall?

This is "a tale of people and British bikes", but within a gorgeous Mediterranean setting that makes me jealous every time I see photos of them rebuilding engines "al fresco" under their lemon tree (see this, this and this).
These guys are big into their (many) Nortons, but they also have other very interesting rides, including a BSA Rocket Three, not exactly something you see every day.
Their hands-on approach is encouraging for anyone thinking of getting involved with the joys and sorrows of British motorcycle ownership, and their enthusiasm in sharing what they do and learn is refreshing.
Do yourselves a favour and check them out, here: http://thomasdunstall.blogspot.it/
Hopefully we'll be doing a joint feature just as soon as I get my Fastback on the road again...
Bravi ragazzi.

Copper (Cu), atomic number 29.

Long story short, the name is derived from Cyprus, and if you've ever been there, you've probably seen the rocky cliffs over the Mediterranean, exposed to the elements and boasting a remarkable display of verdigris. If, however, you've never been to Cyprus, I highly recommend it.
But I digress. I started thinking about copper when I received this parcel from JS Motorsport:

This is a thicker copper head gasket than the standard one, and it even comes with a little bit of very thin copper wire (that's a story for another time). Neat!

I won't get into the "copper vs. flame-ring" gasket debate, which will likely go on ad infinitum, however there are reasons for why I chose a thicker gasket, but we'll discuss all that when it's time to fit this thing.

Fitting the cylinder block; for real this time.

More progress. I started by borrowing Witold's circlip pliers and some Versachem Mega Grey.

As I mentioned, the rings compressor band I have is near-useless, so I did it oldschool and used my fingernails to feed the rings into the grooves one by one, as I lowered the piston into the bore.

Time to fit the first "inner" circlip.

The other "inner" circlip, on piston 2, goes in before I fit the piston into the bore, or there'd be no room to do it otherwise. Piston 2 goes into its bore, again just using my fingernails. At this point I'm thinking of how I can repurpose that ring compressor as a toilet roll holder.

Ok, both pistons are a good fit, they rotate freely and the rings are all where they're supposed to be.
Now for the fun part: using whatever I had around the garage, I propped up the cylinder block just long enough to line up the conrods and insert the wrist pins. Total time? 2 seconds for each side.

Honestly, I don't know why you'd go to the trouble of doing it the other way 'round, installing the pistons, rings and circlips on the conrods and then trying to fit the whole cylinder block over them. That's just nuts. Instead, the way I (and countless others, of course) did it, means that you can keep a close eye on each single ring, take your time and avoid any sort of stress (mechanical or otherwise) for a much neater fit.
Then, the "outer" circlips and that's it, the block is ready to be lowered down.

This particular cylinder block is to be fitted without the conventional paper gasket. You could use a copper base plate if you wanted to, especially to lower compression, but in this case the aforementioned Mega Grey should be all that's needed. Whilst omitting a gasket here may seem unorthodox, I have seen it done successfully in the past, specifically on our Moto Morini 500. Provided the surfaces are true, and that the sealant is applied correctly, there shouldn't be any leaks. Unfortunately there is only one way to know for sure, so... watch this space.

I used one of my trusty luggage straps to hold the cylinder in place while the sealant set, then I went about bolting everything down. Here's an inconvenient truth: because of the shape of the flange, fins and some of the fasteners, I don't think you can use a torque wrench here.
Perhaps some exotic type of tool exists (an extended 12-point crow foot insert?) that allows you to do that, but I don't have it. Instead, what I did was to follow the tightening sequence and go around it a few times (a lot of times to be honest) progressively and as carefully as I could.

I could see the excess sealant gradually being squeezed out, and I reckon I was careful with the quantities I used around the oil return hole, as well as all the way around the inner edge of the mating flange. Again, only one way to find out if I've done a good job or if I've really messed up.
So, right now the cylinder block is snugged down, I don't think I've forgotten anything (cam followers, locating plates, bolts, "safety"wire, pistons, wrist pins, circlips... what am I missing?) and I even managed to put the pistons in the right way around!

Trust me, getting them mixed up is easier than you might think...
If all of the above is correct, I'm one step closer to putting the motorcycle back on the road. Incidentally, I've carefully tried the kickstart and everything is rotating freely.

All of this really didn't take long, which goes to show that if I had time (and all the parts ready) I could have had this all done in just a few days, a week tops, including all the other touch-ups and small fixes I have on my list. Anyway, even doing a little bit at a time is enjoyable, so I can't complain.
Next up will be getting the cylinder head ready to fit, and we'll also have a stab at annealing a copper gasket, oooh!

Finally, some progress.

I've started by putting some lockwire through the four bolts for the cam-follower locating plates, although this isn't actual safetying, in aviation terms. That, I must confess, rubs me the wrong way, but unfortunately because of the extremely narrow gap between the bolts, there simply isn't enough room for anything but the half-assed job you see below (although, shockingly, I have seen much worse):

At least you can see the nice cross-hatch finish on the bore.
Now, if you want to understand what proper lockwire is all about, do yourselves a favour and have a shufti here: Jet Tech: Lockwire  (I know, it's awesome).

Then I fitted the piston rings: always pay close attention to any markings (usually dots, or the word 'top') and/or any bevels on the rings, and always refer to the manufacturer's instructions. In this case it was very easy, and the rings were clearly and conveniently packaged according to their location on the piston. Naturally, you should stagger the gaps as much and as evenly as possible to ensure optimal oil retention and prevent blowing smoke. That would be very annoying.
Look, in general, just read the damn instructions and do what the manufacturer says. When you start making your own parts, then you can do whatever you want, but until then, that little instructions sheet is smarter than you.

I'm using a really crappy rings compressor to get the pistons into the bores, on the bench - as opposed to fitting the pistons on the conrods, and then trying to fit the cylinder block on free-flopping pistons whilst trying not to snap the rings. To me, at least on paper, this sounds like a neater approach, but I can always do it the other way if I don't like it, we'll see. Anyway, like I said, this is a really low-quality tool that I bought online for very little money. I might end up using my fingernails instead.

"Ah, nuts!"

This is why it pays to keep a close eye on your motorcycle folks:

I was removing the crankcase/cylinders studs the other day when I noticed this little fella waaay out. I instinctively pushed it back in as if it were nothing, but then thought "hold on a second".

And then I went over to the timing side and noticed that this other nut disappeared:

That one isn't too much of a problem, I can just replace it (it's the one for the stud holding the primary chaincase), but the rear engine mounting bolt is a problem: because it has been rattling around in there for who knows how long (hundreds of miles? Thousands of miles??) the threads have been totally flattened and the bolt must be replaced. The problem is that the only way to get it out is to remove the ENTIRE primary chaincase, transmission, clutch, alternator, etc.
It is a huge load of work (potentially dangerous as you're messing around with the three retaining bolts in the crankcase, not to mention crankshaft and layshaft alingnment, rotor nut, woodruff keys, diaphragm spring, etc.) and all just to replace one bolt.
I mean, there's no other way to do this properly. But anyway, one thing at a time, I'll finish the top end first and then see what I can do about this.

I may need to get creative here, purists be warned.

So, let's not forget that just because you don't feel vibration on a Commando, that doesn't mean all those horses aren't constantly trying to break free of the pen.

Fitting the cylinder block.

I was just about to fit all the various studs and bolts for the new cylinders when I thought it might be interesting, if not necessarily useful, to point out where each part goes.

Disclaimer: I think this is correct, but of course I could be wrong, so if in doubt contact the manufacturer.

Anyway, as you'll see the fixing kit that comes with the cylinder block is very comprehensive and there's really no mistaking where everything goes.
First of all, you have to remove all the crankcase studs except for the three at the front: since the mounting flange on the new cylinders is the same as the old, there would be no point changing the hardware.
This is also a good time to really get that crankcase flange nice and clean, by the way.

Now for the rest of the fasteners:
ß The two stepped studs (3/8"unc on one end, and 5/16"unf on the other) go at the very rear of the cylinders/crankcase and come with their 12-point locknuts (you'll notice that they're slightly ovalised to provide resistance);
ß The four long Allen bolts go at the sides of the barrels, securing the cylinder block to the crankcase. Note that no washers are provided here, as only some oil under the bolt heads and on the threads is required (on a standard 850 cylinder you would use washer 016213);
ß The three large dark studs go on the underside of the head, two at the front, one at the rear, and are secured with the exotic 12-point nuts. These are probably made of Unobtanium;
ß The two smallest studs with conventional nyloc nuts are threaded into the cylinder block, in front of the pushrod tunnels;
ß The four shorter Allen bolts go at the sides of the head, securing it to the cylinders. ; and
ß Finally, the single dark Allen bolt is the number 1 in the tightening sequence and secures the center-most point of the head to the cylinder block.

Incidentally, the two really big holes are for the pistons... just sayin'.

Fine work.

Check it out, I got the cylinder block back from SRM!

The parcel arrived ages ago, but I've only been able to get to it now, so in fairness it took them no time at all to send it back to me.
Something else worth noting (I should have taken photos as I opened it, sorry!) is that it was all packaged really, really well: plenty of shockproof chips and bubblewrap, reinforced tape everywhere, cardboard "plates" around the cylinders, etc.
There are also the pistons, rings and cam followers.

So, what was all this for? The boys gapped the rings for me, and honed the bores for the correct clearance (0.005").
They also honed the cam follower tunnels so now everything fits as it should. The more keen-eyed will have noticed that the four retaining bolts are not safety-wired, don't worry, I'll get that done properly.
This is a close-up of one of the bores, where you should be able to see the plateau honed finish (don't worry about what looks like imperfections, those are actually just WD-40 bubbles).

And this is a (blurry) close-up of the oil return passage, behind the number 2 cylinder: no witchcraft here, it's just a tunnel, but you must make sure it is perfectly clean, free of anything that might obstruct oil, and that it lines up with the corresponding passages in the head and crankcase.

It all looks and feels really good, and really clean. The peace of mind of knowing the job has been done right will be something I'll always enjoy when riding.
That way I can be confident with the throttle, instead of worrying about how close I might be to catastrophic engine failure.

Well worth the short wait and highly recommended to anyone looking for a proper engineering shop.

Patina.