I have recently bought and just picked up an Ariel square four from 1949 according to the logbook that came with, I am not sure if I will go for a full restauration or try and keep the cosmetic state as it is.
I would like to ask here if you can recommend any sort of documentation that can be of help during the disassembly and rebuild.
Also I am wondering about the siamese style exhaust system on it, as I can only find pictures of square fours with twin exhaust systems.
That looks like a nicely original 1950 model to me. These would have been on sale
from the last couple of months of 1949 on so the 1949 logbook date could well
be correct. As to the siamese pipes I expect it spent a good part of its life
hauling a sidecar in which case you may well find quite a small engine
dprocket when you open things up and rather stronger springs in the forks
and plungers. The registration is from Northampton.
Some more pictures would be interesting too.
I can recommend joining the owners club as a source of information as they have
online copies of all the works manuals and a host of other information too.
I can confirm that it is a 1949 model from the numbers that were listed by H&H, although as Will says it has the short headlamp ears and steel speedo mount that were features of the 1950 models. There is lots of info on this forum and much literature in the club's library, free to members. Siamese pipes were standard fitment on the 1939-40 4G (iron model) but not available from the factory for the MKI. Try not to restore it, give it a good clean and a mechanical restoration. I have several bikes like this and they are always admired by the general public more than shiny restorations.
Roger Gwynn, caretaker of the club's works drawings and machine register, membership secretary 2015-26. Director of AOMCC, Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired. (roger@arielownersmcc.com)
Ignoring whatever else might, or might not, be needed on the bike, it is vital that you strip the engine completely and clean out the tiny sludge traps in the crankshafts. You also need to get all the engine internals as clean as you possibly can do and fit a filter in the oil return line.
This is standard advice for all new Square Four owners. From time to time someone ignores it with the result that the engine blows up within about 500 miles when the black coating within the engine makes its way into the sludge traps, blocks them and starves the engine of oil.
A Square Four is, in my opinion, unbeatable once it is properly sorted out.
Paul Jameson
34 OHC 4F 600 (project), 35 LG 250, 37 RH500, 52 ex ISDT KHA, 54 KH(A), 75 Healey 1000/4.
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist (but not Machine Registrar), Gauges and Clocks Spares Organiser.
JacobD wrote: Mon Nov 02, 2026 7:48 pm
...I would like to ask here if you can recommend any sort of documentation that can be of help during the disassembly and rebuild.
The nearest to a workshop manual are the Waller 'Ariel' books (originally published by Pearson). These were always a bit behind new models, I expect you'll need a 3rd edition (March 1952) or maybe even a 4th edition (November 1952). Originals 'Wallers' come up fairly often on ebay UK.
There are also new reprints of these available via Clymer/Veloce, see for example: https://www.ebay.co.uk/itm/297333441048
And there's always Drags' website (if you've not stumbled across it already) ! https://draganfly.co.uk/
Thanks all for your time to respond, I have found the Draganfly webshop and ordered a manual for the bike.
I will first do a bit of reading before I start working on the bike, I have given it a good spray with WD40 so far and managed to free up the fuel filler cap, which was full with a black tar like substance, may it was put in there for preservation purpose, I have poured in a few litres of fuel to loosen it up.
The bike is complete and other than a slight bend in the fron fender and a damaged primary drive cover there is no damage, so I think I will keep the cosmetics state as it is as much as possible, and yes the engine will fully stripped down and cleaned and serviced where needed.
Last edited by JacobD on Tue Nov 03, 2026 7:05 pm, edited 1 time in total.
I only had a quick look when I saw this on the auction site but now I see that in addition to the later fork parts it has a pre-1949 rear number plate fastened to a 1951-53 rear mudguard. The petrol tank is also the 1950 only version as when the speedo was moved from the tank to the forks it was not possible to see the ammeter or operate the light switch, so these were moved to the tank and the ignition switch was combined with the lighting switch. In 1949 the ignition switch was mounted on the side car lug under the seat. In 1951 a cast alloy top yoke replaced the steel speedo bracket and the longer headlamp ears were brought back so the ammeter and light switch could return to their rightful places!
These things may or may not matter to you and it doesn't to us but you should be aware of them apart from "you know that bit is wrong" to buying parts for it.
Roger Gwynn, caretaker of the club's works drawings and machine register, membership secretary 2015-26. Director of AOMCC, Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired. (roger@arielownersmcc.com)
