The mechanical masterpiece – the AJS Big Port – is without a doubt, one of the most famous Wolverhampton-inspired machines of all time. It was a bike that packed a punch, and was revered for being a potent force on the track. This is a short trip back in time to look at this iconic machine that had one heck of a competitive spirit.
Photo credit: Richard Wray
The first overhead-valve creation surfaced from the Stevens Bros workshops in 1920 as a 349cc racer for the Isle of Man TT. The machines were unreliable that year, but showed some serious promise. AJS went back to the drawing board and in 1921, the bikes were back to their AJS-type reliability. The result was an outstandingly nimble and fast machine that monopolised the 1921 Junior TT. Eric Williams won the race and AJS-ridden motorcycles secured second, third and fourth places. The most impressive achievement, however, were the exploits in the Senior race. AJS factory rider Howard Davies rode the sensational 350 in the big boy race, and took the chequered flag, beating the 500cc Indians of Dixon and Le Vack. Davies remains the only rider to win the Senior TT on a Junior machine… this was the start of the journey of a very special motorcycle.
A 1923 AJS Big Port. Photo credit: John Tindle.
In 1922, the diameter of the big-bore exhaust was enlarged to a diameter of 2 inches, and in November the firm announced that their race-derived, and race-proven 350cc overhead valve machine would be available to the general public for the 1923 season. The catalogued road-racer was a hit, and, characterised by its enormous exhaust port and pipe, it was quickly nick-named the “Big Port” – a term coined by Joe Stevens Junior. The name stuck and became associated with the roadster versions which followed. The bike was quick and nimble, and a favourite for club racing, being good for 80mph +. The standard sporting machine had T.T. pattern handlebars and footboards, and the stripped sporting machine had no kick-starter or side valance to the front mudguard, but included a lighter chain-case.
“More than once criticisms have been heard owing to the fact that the makers of AJS have repeatedly won the Tourist Trophy Race with an overhead valve model which was not available on the open market” remarked the Motor Cycle magazine. “Nevertheless the manufacturer acted wisely, for they felt that until the experimental machines had been reduced to a form which was safe in the hands of the public it was better not to sell them”.
In 1924 the 349cc OHV was appointed as the “B3”, a motorcycle ready for fast road or racing use. There was another option, where customers could specify the limited production B4 – a super sports mount with a higher compression ratio and no kick-starter.
A 1924 AJS Big Port. Photo credit: Yesterdays
The 1925 production machines were prepared in readiness for the Olympia show. The models were given a new letter prefix, starting with the letter E, and the Big Port was listed as the E6 and the E7 – the standard machine, and the racer. The new Big Port had a modified cylinder head, which featured a reduced exhaust port diameter, and a wider inlet port. A binks carb replaced the earlier Amac version and lubrication was improved with a positive feed to the big end. There was also the optional extra of a new mechanical Pilgrim Pump. The more sporting E7 could be customised to suit the rider, which could include a straight through pipe for that extra bark. The 1925 T.T. was an upbeat year for AJS. In the Junior, Jimmy Simpson had the best race, finishing in third on a race-derived Big Port.
A 1925 AJS Big Port. Photo credit: Andy Tiernan Classics
For the 1926 season there were no less than three Big Port options – a standard roadster (the G6), the Sports Special (the G7), and one very special bike set up for pure race mode (the GR7). The standard machine used plain bushes to run the main-shafts and timing gear, whereas the hot models used ball and roller bearings. The raucous GR7, created for competition work, received two pistons – the first which was fitted to the bike, featured a less-pronounced dome for long distance events, while the other was more suited to short speed events such as sprints and hill-climbs, and was intended to be used with alcohol based fuel.
A 1926 AJS Big Port (G6). Photo credit: Bonhams Motorcycle Department.
AJS continued to have strong results in events on the continent for the next couple of years, with thanks to the Big Port.
In 1927, the catalogue featured two versions of the 350 OHV – the H6 roadster, and the racing version, the H7. The H featured a reconfigured cylinder head – work that seemed to have become an annual ritual for the Wolverhampton works. There were updates to the inlet and exhaust ports and a mechanical Pilgrim oil pump now came as standard. The gearbox had also been uprated and the frame modified, with the headstock being enlarged. The H7 racer featured a specially tuned cylinder head, a higher compression ratio, and ball-race bearings for the timing gear shafts. There were was also an options list for the components such as the handlebars, exhausts and tanks.
A 1927 AJS Big Port. Photo credit: Paul Jenkinson
In the 1928 the Big Port was coded the K6 and KR6 and this was to be the final year before AJS moved to the more popular and fashionable (at the time!) saddle tank. At this point in its life, the fiery machine was up against the new overhead-camshaft (OHC) bikes – in true AJS style, these were fast, raucous beasts and a mild threat to the iconic 350 OHV.
The factory still put time and effort into the K series Big Port, which received modification to the top half of the motor, primarily the shift from a strapped down head to a four-stud fixing. There was also an update to the bottom end which now had plain phosphor bronze bushes housed in a wider crankcase; and as such there were modifications to the frame to accommodate the new assembly.
In its relatively short life, the Big Port was a mainstay of AJS and kept them on the map of world competition in the early 20s, when the scene was fierce and competitive. It was also a handy tool for the clubman and privateer with its racer-on-the-road performance.
As Ludwig Mies van der Rohe once said, “less is more”.… and this quite nicely sums up what the Big Port is all about.
an article by The Girder Club
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