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Bike Review - Posted 28th November 2012
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AJS Model 20 / Matchless G9

Almost all the major British motorcycle marques built heavyweight parallel twins in the post-war period. There's always plenty said about the 650s, but the 500 twins tend to be overlooked...

Think AJS, or indeed Matchless twins, and most folk instantly conjure visions of coffee shop racers and the 650 CSRs, fast and famously fragile if unmaintained. AJS in fact built a longer line of pushrod 500cc twins, the Model 20 and Matchless G9, and they offer truly good value to today's classic rider.

Mathless seats always look too big to me... Matchless G9 on sale privately for £4250

There are no rigid twins, and AJS never went down the bodger's blind alley that is the plunger frame, which maybe makes your choice a little easier. Early twins bounced their rear wheels beneath a pair of AMC's own 'candlestick' rear units, changed those to their own tubby jampots in 1951, and finally went the Girling route in 1957. The later the year, the better they steer, generally speaking, although they also accumulate more mass as the years roll by.

The 498cc OHV engine's design was good right from the start; separate barrels and heads, the famous centre main bearing, no external oil lines; alloy heads right from the start and capable of being really rather good, making the most of 26bhp or thereabouts. Gearboxes were by Burman until 1957 when the famously fine AMC four-speed gearbox appeared (and stayed in production until the last Norton Commando in 1978 or so).

At least the front mudguard fits... Matchless G9 on sale privately for £4750

Notably comfortable, long-range riders let down by styling which was restrained and which failed to fit decent brakes until 1964, by which time the Model 20 was out of production. 60mph cruising should be fine; 90mph might be available to the mechanically insensitive. Inevitably slower than its 600 and 650 siblings, the 500 twin was considered by many riders to be the sweeter machine if a little less lively.

Said Cyril Ayton; 'though it had a true top speed of no more than 84mph, a late 1940s / early 1950s G9 was a prodigious before-the-wind or downhill revver. In the right conditions - for example, during a long descent of a Highland pass - it would reach 100mph. Following several of those highland flings at around 100mph, the G9 had the good sense to blow a gasket and was returned to London from Inverness by train…'

Token AJS. Only one photo, sorry... 1957 Model 20 AJS at Yeomans
AJS 500s on

When seeking a Model 20 or G9 to buy you will find squadrons of 600 and 650 twins and 350 and 500 singles, but rather fewer 500 twins to choose between. So sellers tend to be firm on price and while a roadworthy Model 20 isn't worth as much as a Model 31 (ditto a G9 and a G12) it will fetch upward of £3000, with smart ones selling for a grand more. G9s are more common than Model 20s, so red bikes tend to cost a little less than blue ones.

Yeomans Motorcycles unearthed a 1957 Model 20 in autumn 2012 which had been stored for three decades and needs minimal attention to return to roadgoing condition: yours for £2950. Or you could buy a recently restored to concours condition (but not taxed or MoT'd) 1954 G9 from a private seller who was asking £4750 for it. That might have been asking just a touch too much…

Wrong seat fits better than standard one... Bitsa on sale at Bonhams

Meanwhile, a rather smart, ready to ride, taxed and tested 1952 G9 was offered on eBay in November 2012: the seller was hoping for £4250 for it after a full nut-and-bolt rebuild but the bidding stalled at £2350. Or if you fancied finishing off the job yourself, an almost-finished project, recently painted in a quite remarkable shade of red, sold at Bonhams auction earlier in the year for £1500.

A right bitsa which comprised the frame from a 1960 350 single, the crankcases from a 1961 AJS Model 31CSR, G9 internals and a 1950s Burman gearbox, bizarrely painted a brilliant shade of blue, fetched £1150 in autumn 2012, again at a Bonhams auction. (Bikes like this one really should come with a barge pole included in the price, but might suit someone handy with spanners who enjoys what we euphemistically call 'a challenge').

Change the oil and off you go. Probably... Nicer Project on sale at Bonhams

A much nicer project was sold in February 2012 at Bonhams' Shepton Mallet sale. This handsome old beast fetched £1955 and last changed hands in 1978. Let's hope whoever restores it manages not to destroy all that originality - although we will concede that perhaps the saddle needs re-covering, and the tyres might benefit from a breath of fresh air…


Words Frank Westworth and Rowena Hoseason
Photos: RC RChive,

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