Wednesday, September 03, 2008

AJS 'BIG PORT'

John de Kruif sent me a lovely little book, 'Zo Was De Tijd Motoren' (Spaarnestad Fotoarchief te Haarlem, 2004), photographs of motorcycling in Holland from 1913 - 1960. I was especially intrigued by an intimate shot (above), titled 'Klunder inspects his motor before the Assen TT, 1927'. The motorcycle is a 1927 AJS H8 'Big Port' 500cccc racer, complete with pannier petrol tanks bolted together, and an auxiliary oil 'pump' on the separate oil tank. I've always been a fan of the Big Port (so called due to its relatively large exhaust pipe), and owned one a few years ago, which I'll discuss later.

What struck me about this photo was that Brian Verrall had a really nice racing AJS, which wasn't included in last weekend's auction, as an English collector had already 'spoken for' the machine before Brian's untimely death. I had taken a photo in a very similar position to record the bike, as it was such a gem, with all the right period racing goodies. Brian's machine wasn't a 'works' racer, but it did have some racing history. 'Pannier tank' AJS Big Ports are fairly rare (I've only seen one other, at Ivan Rhodes' house - Ivan isn't a one-make man, and has always had an AJS or two around the house). I apologize for the lousy view of the Verrall machine - it was crammed into the garage with a lot of other bikes, and I did the best I could.

As you can see, the pannier tanks bolt together laterally, clamping onto the frame tubes, which makes for a cobby but race-sexy (have I invented a new word?) look. There are a few notable differences between the two machines - Brian's bike has a 3-spoke steering damper knob (of unknown make, but I have an identical one which has a W S on the underside), whereas the Assen machine has a brass Andre damper. Klunder's bike also has a tin toolbox on the tank, rather than the leather item, and a Rexine covered saddle, again instead of leather.

These early Big Ports use an inverted U-shaped steel stirrup to hold down the cylinder head and barrel - there are only two nuts to loosen when removing the head, making top end inspection literally a 5 minute operation. There are no cylinder barrel base nuts, it all comes free very easily. The secondary oil pump on the side of the oil tank is operated by a small foot pedal on the timing side of the machine, and is used when the bike is being run hard and need an extra shot lubrication. A standard Pilgrim type oil metering device is attached to the engine as well, which under normal touring use is all the oil needed. The standard H6 (as seen below, taken at the Banbury Run) has no separate oil tank; only racing machines, or motorcycles with racing pretensions, used the oil tank. The Pilgrim oil pump is clearly seen on the timing chaincase.

The legend of the Big Port began in 1921, when Howard R. Davies (later to make his own racer, the HRD) had the gall to win the SENIOR (500cc) Isle of Man TT on a 350cc machine - a unique event. Howard Davies deserves his own post, as he began his competition career at age 18 for Sunbeam, tying for 2nd place at the Isle of Man. He was competition manager for AJS after WW1, and as AJS didn't make a 500cc machine (and they wouldn't let him race another marque while in their employ), he simply used the same 350cc engine in both the Junior (where he won 2nd, due to a puncture) and Senior TT's, installed in a different chassis (that was one special engine!).
In 1922, AJS again gained 1-2 in the TT, using machines with an even larger exhaust (2 5/8"), which gained them the nickname 'Big Port' (actually coined by Joe Stevens Jr, in charge of racing at the factory). AJS refused to capitalize on this catchy name, and finally introduced a replica of their racing machine for the 1923 season as the '2 3/4hp Three Speed Overhead Valve TT Model', listed at £87. Some claimed it was 'about time', as the Ajays had raced ohv machines since 1920, but had only sidevalves in production. This first Big Port used an Amac carb, but subsequent models used a distinctive screw-on brass Binks carb. In 1926, the GR7 Racing used a stiffened crankcase and ball main bearings (rather than the plain bushes of all other models), plus goodies like alloy clutch plates, racing handlebars, and a special cylinder head, plus two pistons - one for alcohol, one for petrol. The special racing pannier petrol tank became available in 1927 for the H7 Racing model (which doesn't appear in catalogs), holding 3.5 gallons, and including a metal toolbox on top.

In 1928, the 'K6' model had a more conventional bolted-down cylinder barrel, using 4 studs to the crankcase with the head bolted to the barrel, and a revised rocker arm system (alloy rockers were used instead of the previous steel), and a special racing model (KR6) was introduced very late in the season when the factory reverted to the ohv Big Ports at the Isle of Man TT, after discovering their new ohc K7 racer was underdeveloped (a result of ignorance regarding cam timing - AJS used the old ohv cam profile in the overhead cambox, but found a decrease in power... eventually they realized that 'valve float' accounted for much of the Big Port's good breathing, and the ohc mechanism 'cured' the float. It wasn't until Eugene Goodman at Veloce used a strobelight on a K-series engine that ohc valve dynamics were revealed) .
I owned a standard K6, which can be seen in the last photo. It was my first 'flat tanker', and the light weight made for a very lively and fun bike, as the handling was excellent and acceleration was very good for such an old machine. The brakes were pathetic, but better than some 20's bikes (at least they're drums!) - they didn't see much use anyway. I found that my Big Port would top out at 72mph (equalling the catalog claimed maximum for this model), and could be hustled right along on level swervery, but the bike lost urge on our many hills, and I was impatient at the time. Wanting to remain with 20's machinery, I began to seek out pukka racing motorcycles, and found they did in fact possess a more pleasing turn of speed... a pukka racing Big Port would be just the thing...

2 comments:

1967 R50/2 said...

Great article. They carb just looks so tiny in comparison to later carbs.

Anonymous said...

Hi Paul, I thought you would like [the book] as the pictures are great and were all taken in Holland. The Dutch must have been very keen motorcyclist a
century ago as there seems to be a never ending supply of pics of people riding quite expensive bikes such as Harleys and Indians. I have a pic of my granddad riding an Indian with his uncle. Sadly, my dad could only afford an NSU
twostroke and I only have a pic of myself as a baby sitting on that thing.
John de Kruif