1950 500cc AJS 18S

Frame No.          47806

Engine Nos.       50/18   14359,    50/18S 12535

Burman gearboxes, Nos.      G88 J 46,  G79 B49,  G2  D47

This is the bike that I rode in the 1960’s – and never thought to photograph! The only visible difference of the original state of my 18S and the 1949 version above is that mine was fitted with a spring pillion seat rather than a bum pad.

Part numbers for the finished version of this machine will depend on which of the various available pieces are chosen for the final re-build.

Originally the bike was bought complete for £25 from McIntosh’s wrecker’s yard in Geelong in 1959. It looked only a bit weathered, however it turned out on close (and seriously alarmed!) inspection to have a broken left-hand lower frame member and had also broken a piston, which was still in fragments in the crankcase tearing up the main bearings and oil pump; a new piston had been fitted without cleaning out the wreckage!

A spare frame was bought from Belton’s, Elizabeth Street, Melbourne and the wreckage of another rigid frame version which a local farmer had crashed into a loco at the Irrewarra railway crossing (and survived!(barely)), was bought for £5 and some of these parts (essentially the crankcase) served to get my machine going again. The bike was on the road for the beginning of the 1962 academic year.

Surplus parts (including the original frame, of which I had later neatly sleeved and brazed the lower member), were appropriated, not entirely with permission, by my younger brother Keith to build up a surprisingly effective ‘chook chaser’ for paddock use.

His semi-larceny must however be forgiven, as somewhere along the line it seems that he has acquired various other parts, which may help considerably in maintaining our machines.

My intention with the bike had been to build a ‘café racer’, so the compression was raised to about 8.5:1 by removing the compression plate that the factory had fitted under the cylinder barrel to cope with the noxious ‘pool petrol’ of the WWII/early 1950’s period and fitting a higher-top piston. It already had an alloy head, so this was ported & polished, a slightly bigger bore Amal carburettor and a set of ‘CR’-style high-lift cams were acquired for the job.

Early shuttle damped Norton “Road-Holder” forks and front wheel were fitted, with later model ‘Jam-Pot’ rear suspension units in place of the 1950 ‘Candlestick’ version.

The frame was laboriously scraped down and chrome plated. Painting the tank, chain guards etc. in matte black, fitting alloy mudguards, and a “twin seat’ instead of the original saddle completed the décor. At that time second-hand ‘cling rubber’ Avon road racing tyres could be acquired from riders returning from the European season, and a pair of these gave it superb handling (well, for its time!).

I was no end proud of this bike, and with a little justice, as it did attract favourable attention. It also went like the clappers, and could easily crack 90 mph on the flat. It is a pity that I never timed it properly or took a photo’ of it.  For a short time I had the compression up to about 9.5:1 and ran it on 50/50 petrol/benzole, but it was too intractable for city use and tended to oil the plug in traffic. In later decades, looking at the work done, the job was really a little rough (but honest!) Let’s see if I can do better this time.

The bike was ‘blown up’ later in the 1960’s when a piston circlip came adrift. It was dismantled for a full re-furbish, which never actually happened due to distractions such as work, marriage, etc. A full set of parts are here, with a number of extras acquired over the years, but they need to be picked over and selected  (with any necessary reconstruction and repairs) for a complete rebuild, with the intention of going further along the 1960’s period ‘café racer’ theme this time. One plan that was never realised in the original project was to rebuild the front hub (including parts from a spare that is available) to house twin brake drums á la Vincent HRD. Alloy rims fore and aft would be desirable to complement that job.

In 2008 a friend gave me a number of parts he had not got around to using for a café racer himself; an elegant jelly-mould fibreglass tank, a racing seat frame and headlamp fairing, a pair of alloy rear-mount foot pegs & gear change and a pair of alloy guards.  Some or all of these should be adaptable for the project.


3 comments on “AJS 18S

  1. Gary Calvert says:

    Hi Colin
    Thanks for the reply, yes its always good to keep what spares you have as you never know when you might need them.Are you still in Darwin and are there many old scoots up that way (Vintage M/C clubs) my bike is still running OK at present but sometime in the future I would like to overhaul the motor so will probably need to re-skirt the bore & new piston as I would like her to keep motoring for another 60 years. Do you do most of the major repairs yourself or do you know of a reliable mechanic that is still upto working on such machines
    If you know of someone who is good with these types of motors please let me know as there are a few people in the AJSMOC in Aust. who could benefit from there work. Again many thanks for replying and for any hep you can give.
    Gary C

  2. Gary Calvert, Sunshine Coast Qld. says:

    Hi Colin
    Fascinating stories and great that you relay the history of each machine.
    Your stable of bikes is quite impressive, some I have and some I would love to own also (Honda CX500T or CX650T )
    The reason for my contact with you is to ask if you still have your 1950 AJS 18S, as I have my fathers bike also that he owned from new. I was wondering if you still have the old candlestick rear shocks or any other parts that may be surplus to your requirements that may be taking up valuable realestate in your workshop and weather you would consider selling them.

    Many thanks

    Gary C

    • Colin De La Rue says:

      G’day Gary,

      I still have the 50/18S AJS (in pieces) but I am afraid the candlestick shocks were traded off for a set of jampots
      in my original rebuild as they really were rather frail and not very reliable. Of course it didn’t occur to me that they
      might become a desirable rarity in the future.
      I do have some parts, but as my brother and cousin also have AJS’s of that vintage we tend to be very parsimonious
      with our spares. Perhaps we could swap some emails over this.
      Colin DLR

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