AJS Model 18 & Matchless G80

Heavyweight singles buyers guide


▲ AJS Model 18CS. The "C" stands for "competition", and the "S" stands for "spring" or "suspension". The Yanks, especially, liked these mild off-roaders and bought thousands. The gearbox is a conventional design (mainshaft-layshaft) Burman B52 as used on the AJS 7R OHC racer. The positive-stop mechanism was improved. The clutch too. Aluminium mudguards. Abbreviated fuel tank. Nice.

AMC wire wound pistons


AMC wire-wound piston detail


Wire wound pistons were introduced by AMC in 1948. These featured 18swg high tensile steel wire that was wound five times around an aluminium alloy piston skirt, welded in position (according to author Roy Bacon; others suggest it's merely an interference fit) and ground to size. The idea was to control expansion and allow tighter tolerances. Aside from smoother and more efficient running, the tighter clearances reduced piston slap when starting from cold. Today, most riders are fitting conventional aluminium alloy pistons, largely because no one currently makes replacement wire-wound items. But every once in a while they do turn up on eBay and elsewhere as new-old-stock and are perfectly usable if in good condition.

Other AJS/Matchless model names


In 1965, in an effort to bolster flagging sales, AMC tried to hang different, and clearly more exotic/commanding names on their heavyweight singles

These names included:


Matchless G3 Mercury 350

Matchless Major 500

AJS Model 16 Sceptre 350,

AJS Model 18 Statesman 500


The names appeared in both domestic and overseas catalogues, but they never really caught on. The old denomination had stuck, and it was too late in the day to change.

1951 Matchless brochure


1953 AJS Model 18/Matchless G80


Type: Air-cooled OHV pushrod single
Capacity: 498cc
Bore & Stroke:
82.5mm x 93mm
Power: 26-28bhp (claimed) @ 5800pm
Compression ratio: 6:1
Transmission: 4-speed, multi-plate, Burman

Brakes: Drum front and rear
Electrics: 6-volt, dynamo
Front suspension: Telescopic
Rear suspension: Swinging arm, twin shock absorbers/dampers
Wheels/Tyres: 3.25 x 19-inch front, 4.25 x 19 rear
Weight: 390bs (dry)
Maximum speed: 75-80mph

ajs-heavyweight-single-timing cover


"Badge engineering"? So what's the story, then?


That's the famous AJS logo adorning a Matchless timing cover (above image). That's how many of the Matchless boys view it, anyway. But we don't have a problem with this kind of "badge engineering", largely because it's not as simple as that.

Yes, AJS (founded by Albert John Stevens in 1909) went bust in 1931 and Matchless (owned by the London-based Collier Brothers) bought the spoils. That led to the creation of Associated Motor Cycles, or AMC.

But Matchless didn't simply throw out AJS's ideas, expertise and experience. Instead, they assimilated the Wolverhampton firm into their own outfit and benefited greatly from the acquisition.

In the 1914 Junior TT, for instance, AJS took first, second, third, fourth and sixth place.

In the 1921 TT, AJS took the first four places, and the company notched up numerous other wins thereby consolidating its reputation as a force to be reckoned with.

AJS also built cars, buses and coaches, and later produced the Stevens motorcycles.

In short, AJS was always "out there", and if the business failed commercially, from a technical and competitions perspective, the company was nobody's poor relation.



AMC factory plaque: 9th Sept 2007


That's the date that this plaque was finally screwed to an anonymous looking wall in Plumstead, South East London. It was put there to commemorate the 40th anniversary of the closure of the huge AMC factory. Note that AJS bike production at Plumstead actually ended in 1966. But the Matchless G85CS competition machine (not to be confused with the G80 roadster) continued there until 1969. There were other competition revivals, and in the late 1980s, Les Harris of Racing Spares Ltd in Devon produced a Rotax-powered bike badged as a Matchless G80.


AMC factory Plumstead


In any case, that was a bad time for the British motorcycle industry, and it wasn't a lot of fun for the local population, many of whom were employed at the factory and saw a radical change in their fortunes and expectations.

The knock-on effect also damaged or curtailed many other local businesses which depended on AMC for various forms of contract work.

The plaque was unveiled by Greenwich Councillor Peter Brooks. Also in attendance was Sammy Miller, Colin Seeley, and dozens of ex-AMC engineers, test riders, assembly staff, and club members.

We were there too.

Click the plaque image above for more information.

Fifty pound notes


Buying an AJS Model 18


If you're buying, you've got a fair choice of models, so buy with your eyes. For years—decades even—prices have been pretty reasonable for these 500s. Yes, there have been occasionally spikes (and dips), but the prices always settle back to "affordable" levels, whatever that means to your wallet.

At the present moment (May 2014), a sorted, on-the-road, 500cc AJS Model 18 (swinging arm) will cost around £2,995-£3,500. You might pay £4,000 for a very good one, and even a little more than that for a bike with interesting history/provenance. But we've also seen fairish (project or rolling restoration) examples on offer for just £2,500 The rigid framed bikes will demand another £500 or more across the board.

The alternator models are generally less desirable. The earlier magneto Ajays are more popular, both for their feel and in terms of their classic "quotient".


Living with an AJS Model 18


These singles are easy to live with, but evidently not so easy to fall in love with. Not by the wider biking public anyway. Yes, these motorcycles have their hardcore fans. Which marque doesn't?  But they tend to plod around in a dignified fashion rather than scoot around like Lords of the asphalt. That was all quaint and frugal once upon a time. But today, it presents a lot more challenge on the busy roads where many drivers take no prisoners.

Maintenance is fairly straightforward. All Ajays and Matchlesses have their idiosyncrasies, of course. Awkward nuts and bolts. Puzzling procedures. But nothing that will fox you for very long, not if you're even half-smart. Generally, however, pretty much everything on the bike is accessible, even when you're on your knees in your shed or garage struggling against failing light (don't ask us how we know that).


Parts supply


Parts supply meanwhile is very good. There's a busy AJS and Matchless Owners Club which can usually point you in the right direction for more or less anything you might need.

Tinware's a little scarce, of course. The Indian sub-continent is making some parts of dubious quality. It's not all bad. But it's not all good either. Expect to have some remedial work done after you buy. But if you're stuck for a fuel tank or a mudguard, this Indian stuff might get you back on the road.

Better still, if you can have the original stuff repaired (metal bashed) etc, that's a lot more satisfying.



"The front and rear brake shoes, springs and expanders are interchangeable. The two shoes in each brake are NOT identical, they are 'handed'.


"Harshness in the transmission can be caused by the drum retaining bolts and nuts being loose. Rear wheel spokes will break for the same reason."


— AMC, Maintenance Manual

and Instruction Book for 1954




The brakes, by the way, were never up to much on the early bikes, so try and forgive them. We certainly wouldn't call them dangerous. Just not ideal. That said, you can find more than one rider who's perfectly happy with the available stopping power. But if this is a particular concern for you, choose a much later bike with the Norton brakes and suspension.



Heavyweight singles


... and these bikes are not called heavyweight singles for nothing. They heave in at around 390lbs, which is not much less than a 750cc Triumph T140 Bonneville (for instance), and they stand pretty tall.

That's not necessarily a bad thing, mind. They have lots of road presence, and they leave you in no doubt of which way gravity lies. At Sump, we've always felt pretty confident riding these, and you should too.

But you won't much like regularly hauling a heavyweight single onto its stand if you're of a certain age and/or have a few loose bolts in your knees. If they were twins, of course, the weight wouldn't be a consideration. They'd be considered light. And old British sidevalve singles (say, BSA M20s or Norton 16Hs) weigh about the same, and no one complains there.

But AJS Model 19s or Matchless G80s are judged by a different (1950s) standard, and in that context, they're punching below their weight. There are much lighter options around.

Keep that in mind.

Overall, as we said at the start of this feature, these are great British singles. Mechanically, you'd have to be an idiot not to be able to keep one running. You'd have to be blind not to be able to find spares. And you'd have to be a pretty lousy or unlucky rider if you fall off more than once in a long while.

Forget investment, however. These bikes occupy that familiar space where nothing really happens too quickly or suddenly. Instead, they just plod along and get there in the end. And there's a lot to be said for that.


Specialists and spares


AJS & Matchless Owners Club



AMC Classic Spares





▲ Back to the top


THE 500cc AJS MODEL18, aka the Matchless G80, is arguably the quintessential English post-war heavyweight single. Solid, handsome, competent, economical and reliable, you might be forgiven for feeling the urge to wear a bowler hat and a bow tie when riding one of these about town, or even further afield. Because they'll take you pretty much anywhere you want to go without too much fuss and drama.

The half-litre thumper was a more or less direct development of the WW2 350cc Matchless G3/L, which in turn was developed from the long-stroking Matchless singles of the mid-1930s.


Don't we mean AJS?

No. Matchless (owned by the redoubtable London-based Collier brothers) bought Wolverhampton-based AJS (owned by the Stevens boys) way back in 1931. Seven years on, the Colliers formed Associated Motor Cycles, or AMC, the parent company for other marques that they subsequently assimilated.

Henceforth, AJS and Matchless soon became largely synonymous, or "badge engineered" to use the vernacular.


350cc Matchless G3 for 1946,  Teledraulic fork and rigid frame


AJS announced two OHV singles in June 1945; a 350cc model, and a 500cc. Matchless announced their versions in July, about one month before the Hiroshima bombs, which puts it into some kind of context. Is this Matchless G3/L (above) the prettiest? We think so.


500cc AJS Model 19 for 1948, Teledraulic fork and rigid frame


1948 AJS Model 18. A Matchless by any other name. Features include a patented "Teledraulic fork with three rate springs and shuttle-type hydraulic damping. No maintenance required." Tyres were 19-inch x 3.25 front, and 19-inch x 3.50 rear, both Dunlops, of course.

AJS heavyweight single big end


AJS Model 18 & Matchless G80 development


The recipe for the AJS Model 18 was straightforward enough. Stir-up a long stroking, 82.5mm x 93mm, 498cc, single cylinder pushrod engine. Peel an iron head and barrel for durability and cost control. Chop two ball bearings on the drive side (left side) for "load" and "location", and fit a single roller and a bush on the timing side (right side). Next, sprinkle double coil valve springs up top (hairpin springs after 1949). And season with a Type 89N/IED, 1-3/32inch Amal carburettor.



500cc AJS Model 18 for 1947, rigid frame


AJS Model 18 for 1947.Rigid frame. Teledraulic forks. All iron engine. Pressed steel primary cover. A simple, rugged, long-stroking pushrod (and twin cam) 500cc single served up British style.


Add a pair of heavyweight cast-iron flywheels. Tenderise the compression down to around 6:1. Spice it with a Lucas SR11 magneto (NR11 for competition bikes). Couple the engine to a Burman 4-speed gearbox, and bolt it all into a single downtube steel frame (with a rigid rear end) and let simmer.

Next, take the famous Teledraulic front fork from a 350cc Matchless G3/L. Lace up a pair of 19-inch wheels. Paint the cycle parts appropriately, and you're pretty much ready to serve, hot or cold.

Alternately, a 63mm x 93mm 350cc model (actually 347cc) was available for anyone on a diet. And although this was 1946 and the world was speeding up, the 350cc bikes (which were essentially the same dish on a smaller plate) were far more popular. They were (a) cheaper to buy; (b) adequate for the commuting working man; (c) gave marginally improved fuel consumption; and (d) were generally more docile.


Timing cover from a Model 18 AJS heavyweight single


AJS Model 18 timing cover detailing the chain-driven magneto. Until 1952, a Matchless carried its magneto under the carburettor. After that date, it was shifted forward.


But the 500cc Model 18 was the choice of the tearaway-to-be, or anyone who had red blood in their veins. Trouble was, if you were living in Britain which was still scraping by in full austerity mode, you weren't very likely to get your hands on either motorcycle because exports dominated. That was the price of victory. However, the important thing was that the motorcycles had at least arrived in the civilian market (as opposed to the military), and for eager AJS or Matchless men, it was just a question of time before they got their hands on one.


1950 Competition Matchless G80C, 500cc


1950 Matchless G80C.That "C" for competition, Now with an all aluminium alloy engine, bigger valves, and reworked cams. Two years earlier (1948), the 350cc bikes adopted the 500cc crankcase for improved manufacturing efficiency.


Alternator model Matchless G3, 350cc. !959


1959 Matchless 350cc G3LS.This is an alternator model as evinced by the absence of a magneto on the timing chest. More refined, but less attractive. The AJS 350cc version was pretty much identical, mechanically speaking. The 350s are far more common.



AMC gearboxes were fitted from 1957


1957 AJS Model 18S.Spring frame. Now with an AMC gearbox. A little staid, but ideal for the commuting man of the day. This was the last year of the steel primary cover. That cover was aluminium from 1958. Many riders feel this 1957 model is the perfect all-round choice.


AJS & Matchless heavyweight singles frames


A plunger frame was never on offer. AJS/Matchless moved straight from a (1946) rigid chassis to swinging-arm (1949)—or "spring frame" to use the company-approved terminology. And with it came the "S" designation or suffix, as in: AJS Model 18S.

The frame was a decent enough design, if a little over-engineered. But the AMC manufactured rear shock absorbers/dampers were less than ideal. They began with a slim "candlestick" design which, by 1951, had morphed into the fatter "jampot" type. Neither was up to much and leaked and displayed other irritating eccentricities. It wasn't until 1957 when Girling units gave AJS a rear suspension set-up worthy of the name.


Aluminium engines


An all-aluminium alloy scrambles engine appeared in 1950 c/w hotter cams and bigger valves. AJS had been fielding competition machines since 1946, note, and saw an opportunity to rework them with the all-aluminium power units (aluminium being in short supply until then).

The following season, the road-going models (the roadsters if you prefer), were fitted with aluminium heads as another concession to modernity.




In 1952, the AJS and Matchless marques became more homogenised, visually speaking, when Matchless shifted its magneto position. Originally, the Matchless mag had been located directly under the carburettor. That was an ideal spot for the device to catch stray fuel drips and, potentially, start a fire—or just dissolve the shellac around the wiring. Not good.

But that year (1952) Matchless shifted its magnetos to the forward position beneath the exhaust downpipe where the Ajay mag had always been. Not so great for cylinder cooling perhaps, but overall, it was probably as round as it was square. And suddenly, the livery and tank badges notwithstanding, it was less easy for the average aficionado to spot at a glance, or at least at a distance, their favourite legover.

The dynamo, for both bikes, stayed where it had been from the start, which was between the engine and the gearbox, nestling cosily in that far-from-deal-spot directly under the carb.




1960 AJS Model 18.Alternator engine. AMC gearbox. AMC fork. The pushrod tubes still visible. In 1964, these would be cast into an aluminium barrel (short stroke engine).



1953 AJS Model 18S.Burman 4-speed gearbox detail. Note the generator, top right.


The crankshafts were revamped for 1954 and became both stiffer and lighter, a move that didn't find favour with all fans. The earlier cast-iron cranks gave the bike their famous down-and-dirty slogging character which, arguably, was suddenly lost. Or, at least, diminished.

As post war fuel quality improved, so the compression ratio crept up from 6:1 to 7.3:1 (1956). Not a huge hike, but a welcome performance boost. However, once again many riders felt that something was lost.



Matchless brochure for 1958. Now 7.5:1 for the 350 singles, and 7.3:1 for the 500s.Centre stands only now. Side stands were optional, so check before you buy, especially if lifting one of these is likely to be a problem.


Burman gearbox or AMC gearbox?


Nevertheless, AMC pushed on with its project, slowly improving the recipe and in doing so they put more beef on the bone. The frame, for instance, was strengthened (1956), and AMC fitted a new gearbox of the firm's own design (1957). That meant goodbye to the Burman 4-speeder which had served the firm well for a generation (actually there were three types of Burman; the BA, the CP and the B52). But the new 4-speed AMC 'box was as good—or better according to many. And that same year, the clutch was upgraded for extra bite and efficiency.

Included in the transmission package revamp was a clutch (rubber) shock absorber a la Triumph. This made the crankshaft face-cam shock absorber redundant. Yet again, not everyone appreciated the change and, many riders couldn't feel any real improvement on the street. But the clutch itself was certainly better if only by controlling the oil with improved seals.


Alternator electrics, coil ignition


The following year, 1958, saw a much more obvious change. The old pressed-steel primary chain case, easily capable of turning a trickle into a small flood (if it wasn't fitted properly, which was as much the rule as the exception), was replaced by an aluminium alloy item. The move coincided with (indeed, was driven by)  the switch to alternator electrics.

That numbered the days of the magneto, and introduced more reliable volts with a coil ignition system.

Technically, AMC had done the right thing with this move. Alternators were clearly the way ahead, and ignition coils were cheaper than mags (whose days were numbered by firms such as Lucas, BT-H and Bosch).



AJS Model 18. Alternator model. AMC gearbox with lightened gear change. Note that the pushrods have vanished into the barrel/cylinder head casting.


Starting was now easier too. And overall weight was being cut. Or at least moved elsewhere. Nevertheless, the more conservative biker (small "C") often preferred magneto ignition and enjoyed the separation of lighting from sparks.

In 1960, the frame changed yet again and featured twin downtubes thereby providing a full dual cradle chassis. The alternator, which began as a two-phase unit, picked up an extra phase that year, and the cylinder head was redesigned and offered a hemispherical combustion chamber for improved gas-flowing and thermal efficiency.



AJS Model 18. Aluminium alloy primary drive cover from 1958. The primary chain is still single row. The alternator is a Lucas RM15 unit, good for around 80W. Lucas MA6 ignition coil.


Short stroke engines


In 1964, the engine's bore and stroke changed for the roadsters. The new short-stroke (or, over square stroke) dimensions of 86mm x 85.5mm weren't new. The earlier scrambler and competition models of 1959 had been manufactured with these vital statistics which had given AJS/Matchless a more sporting edge that in turn helped the marque keep up with, and often race ahead of, the competition.

 The cubic capacity was still 498cc, but the character of the engine had changed yet again. The older slogging feel was suddenly a little buzzier. A little freer revving. A little ... well ... younger. Vigorous even.

Over the next few years, AJS tweaked everything that was tweakable. Wheels. Mudguards. Tank badges. Knee grips. And brakes. It seemed as if the firm was on a mission to make its earlier (and much-loved) product unrecognisable in its new format, which it almost was.

Other changes saw the fitment of Norton Roadholder forks, wheels and brakes to these heavyweight singles. Why? because (a) the Norton gear was better, and (b) AMC had bought Norton in 1953 and could rationalise parts manufacture. The result was a much improved motorcycle with a similar 80mph top end, improved stopping at the other end, and slightly better handling in between.

But time was not on the company's side. Twin cylinder engines were in vogue, and big British singles were yesterday's bread. The last Model 18s were built in 1966. They came off the "Colliers" assembly line in Plumstead, South East London, and that was exactly where it all started. But the Matchless G85CS (a lightweight, high-compression, competition-ready G80) was still being built into 1969.


Triumph Bonneville:
World's Coolest
Motorcycle T-shirt


£14.99 plus P&P

Classic bike dealers, engineers, mechanics and experts


Copyright Sump Publishing 2014