Identifying old Douglas motorcycles.

Part 2: 1920s and 1930s (excluding 2-3/4 and 4hp).

Doug Cross, Doug Kephart, October 2004

Version 4.6
You will find the latest version and discussion of this document here - http://www.douglasmotorcycles.net/index.php/topic,489.0.html


To help you navigate, the full set of files in this series is as follows:

Part 1: Models 2-3/4hp, 3-1/2, and 4hp, 1907 to 1926
Latest version and discussion of this document here - http://www.douglasmotorcycles.net/index.php/topic,488.0.html

Part 2: Models of the 1920s and 1930s, excluding models in Part 1
Latest version and discussion of this document here - http://www.douglasmotorcycles.net/index.php/topic,489.0.html

Part 3: Postwar Models, excluding Vespa scooter
Latest version and discussion of this document here - http://www.douglasmotorcycles.net/index.php/topic,490.0.html


Codes and numbers of the main components.

In general during this period, location of the component codes and serial numbers are in the following locations: 

Frame: Side of frame lug under saddle, left or right-hand side depending on model.  Usually terminated by a superimposed capital D and K trademark, though on occasion the trademark precedes the frame code if they ran out of space!

Engine: Top of crankcase alongside magneto.

Gearbox: SV- top side, adjacent to joint for cover.  OHV- Adjacent to mounting pad.


The 1920s models.

After the Great War, Douglas brought out a range of new models, reflecting demand for more power and, towards the end of the decade, the great popularity of dirt-track riding. The Dirt Track (DT) model was a tremendous success, and road-going versions were produced for popular riding - and to allow the bikes to be ridden legally to and from speedway venues! The current fastest classic sprinter around today is Henry Body's bored out DT 500 - with quarter mile finishing speeds above 110 mph, there is virtually no-one who can catch him, even on much more modern bikes. These vintage Dirt Track and Speedway bikes are now extremely valuable, so if you have one, be sure you know what they are worth before parting with it!

Here is what I can find of the codes that identify the different models.

3 1/2 HP OHV Sport, S1 – 500cc OHV, 1921-1923

Year

Max Frame No. or letter code

Max Engine No. or letter code

Gearbox letter code

Any distinguishing features

1921

AF***

AE***

AG***

Gearbox mounted below rear cylinder. Single carburetor high and horizontal with down-swept intake manifold. 68mmx 68mm for 494cc. Kick start lever right-hand side of gearbox.

1922

-

-

-

Single carburetor still high and horizontal but intake manifold now level, circa 1922-23.

1923

-

-

-

Superceded by RA (racing) and OB (sporting, sidecar.)

6HP OHV Sport, S2, HE, 4HE – 733cc OHV, 1923-1924

1923-24

?

CE***

?

As S1 except engine well over square at 83mm x 68mm for 733cc! No known survivors in motorcycles, but variants of engine were used in powered gliders. Only have info showing S2 (solo) offered in 1923. Offered as sidecar combination H.E. (1923) and 4HE (1924).

Model RA - 500cc OHV, 1923-1925

1923-24

DF***

FE***

MG***

Gearbox mounted above rear cylinder, but attached to engine not frame. 68mm x 68mm. Twin carburetors breathing from a central airbox. Hand change and gate mounted off top of airbox.  Under-slung cast alloy oil sump.  No kick start lever.

1925

JF***

WE*** (500cc)

VE*** (600cc)

-

(600cc version not catalogued, available to order)

Model RW - 350cc OHV, 1924-1925

1924

?

?

?

Identical to RA above, except 57mm x 68mm.  No known survivors. 

1925

KF***

XE***

-

 

Model OW - 350cc OHV, 1924-1925

1924

 GF***

IE***

?

57mm x 68mm.  Kick start lever on timing chest. First model where the petrol tank slopes from headstock to saddle. Single updraft carburetor with down-swept intake manifold to each cylinder. Dummy belt rim brakes. Hand shift along side petrol tank. 

1925

?

-

?

Gearbox above rear cylinder, but now attached to frame under saddle, not engine (possibly started in 1924.) Main-shaft at rear of gearbox.

Model OB - 600cc OHV, 1924-1925

1924

HF***

 OE***

PG***

Similar to OW, but 68mm x 82mm. Early catalog pictures shown RA/RW style mounted gearbox, but it is believed all production had gearbox mounted to frame under the saddle. Single updraft carburetor with down-swept intake manifold. Dummy belt rim brakes. Manifold eventually fully jacketed by aluminum casting.

1925

-

-

-

Catalogued with manifold above, but switched to level intake manifold with horizontal carburetor mounted above. 

 I.o.M. Model - 350cc OHV, 1926-1929

1926

NF***

EB***

UG***

350cc was catalogued but bore and stroke not known. Otherwise same as 500/600cc I.o.M Model. Possibly available with VG & SG prefix gearboxes. 

1927-29

UF***

-

-

Shared frame with 500/600cc I.o.M Model. 

Model TT Replica, I.o.M. Model - 500/600cc OHV, 1926-1929

1926

OF***

EA*** (500cc),  EC*** (600cc)

UG***, VG*** (extra-wide ratio)

Twin carburetor with airbox, gently sloping tank top, still has threaded intake and exhaust port gland nuts. Gearbox above rear cylinder mounted to frame under saddle. No kick start provision on I.o.M Models. Early frames have plate rear spindle lugs like OW/OB, later replaced by brazed lugs used subsequently on DT. Available to factory riders in 1925, with the Douglas servo band drum brakes. Main-shaft at front of gearbox. Available to order 750cc. 

1927-29

UF***

FH*** (500cc),  IH*** (600cc),

-

Likely no significant change. 

Model OC - 600cc SV, 1926-1927

1926-27

LF***

ED****

UG***, TG***(wide ratio), SG***(close ratio)

Replaced OB model. Douglas servo band drum brakes. Unlike OB, the main-shaft is now at front of gearbox. With footboards or footrests. Hand shift passes through petrol tank. 

Model EW - 350cc SV and derivatives, 1925-1929

1926

MF12000

YE10000

RG10000

60.8mm x 60mm. Gear change lever through slot in petrol tank; gearbox behind engine. First SV with gently sloping tank top. Gearbox mounts on four studs. With or without electric lighting. Sports version with foot pegs and aluminum pistons. Deluxe version also available. 

1927

MF20000

YE20000

RG/A****, RG/B****, RG/C****

Gearbox clamps around frame tubes.

1928

MF23000

YE22000

-

Called the A28, foot pegs standard. Cloth saddle replaces leather pan. Version called the B28 has detachable cylinder heads (incorporating valve ports), and C28 with same heads and aluminum pistons. 

1929

-

-

-

One model only called A29.  Continues with flat tank to use up stock while other 1929 models get a saddle tank.

Model EW 600, EW 600 Sport, F28, F29 - 600cc SV, 1927-1929

1927

PF****

EH****, S/EH****

WG****

68mm x 82mm. S/* denotes sports model with aluminum pistons, drop handlebars and foot pegs instead of touring handlebars, cast iron pistons, and foot boards. With or without electric lighting. Oil sight glass built into face of timing chest cover, not on top of petrol tank like the 350cc EW. Leather pan saddle. Sometimes called the SB27, catalogued as EW 600. Full duplex front down tubes. Detachable cylinder heads incorporating valve ports.

1928

-

-

-

Steering friction damper under handlebars. Cloth covered sprung saddle. Catalogued as the F28. 

1929

XF****

-

WG****, WG/T***, WG/R***

Saddle tank, necessitating a change to the upper part of the frame. E29 had foot boards, F29 foot pegs and drop handlebars (continuation of Sport model.) Oil sight glass (same unit as mounted on petrol tank of EW) attached to small corbel on face of timing cover. 

Model B28, B29, L29 - 350cc SV, 1928-1930

1928

 

 

 

Colonial version of the A28, not built to 224lb. weight limit. 

1929

WF****

EN****

RG/C*****, RG/L***(L29)

With saddle tank. Engine now sits on large cast aluminum oil sump, no oil sight glass. L29 was a war department model. 

Model D28 - 350cc OHV, 1928-1929

1928

RF***

EI***

XG*****

OHV built on the crankcase of the 350 SV EW. Enclosed pushrods on side of engine (rather than on top like the other OHV models.) Sparkplugs on left. Gearbox below rear cylinder. Flat tank. Hand shift lever mounted down alongside front cylinder. 

1929

VF***

-

-

Saddle tank in celluloid finish.

Model G28/H28 - 500/600cc OHV, 1928-1929

1928

?

?

?

Continuation of OC model unchanged. G28 was 500cc and H28 600cc. Probably continued to used same prefix codes as OC. 

1929

-

-

-

Now called G29 and H29 respectively.

Model DT5/DT6 (Dirt Track), SW5/SW6 (Speedway) - 500/600cc OHV, 1928-1932

1928-29

TF****(DT), FB****(SW)

EL****

YG**** (DT),

UG*** (SW), TG***(SW wide ratio), SG***(SW close ratio)

Gearbox above rear cylinder mounted to frame under saddle; road versions had brakes and clutch. Tall air box, twin Amac carburetors. Oil held in front compartment of petrol tank, hand pump manual oiling only.  62.25mm x 82mm (500cc) and 68mm x 82mm (600cc). Single central spring on front fork. 

1930-32

-

-

-

Small, square airbox with mechanical oil pump, oil drip sight glass mounted on top of airbox. Still has hand pump for auxiliary oiling.

Note: where you see in the tables a code followed by three or more asterisks (e.g., RG/C*****) the number of asterisks indicates the number of digits in the code number, a hyphen (-) indicates 'same as previous year' or 'ditto'. 

The 1930s models.

The Douglas firm went through some rocky times during this period, which is reflected in the wide range of models - and their often extremely short production runs! There may be others that I don't know about - these are what the Club Register reveals.

Models H3, L3, B31, B32 - 350cc SV, 1930-1932

Year

Max Frame No. or letter code

Max Engine No. or letter code

Gearbox letter code

Any distinguishing features

1930

FA****

EN****

RG/C****, RG/E***, RG/G***(H3),  RG/L***(L3, H3)

Continuation of B29. 1930 models with foot boards and celluloid finished petrol tank called the L3 and foot pegs. Deeper mudguards, chromium plated petrol tank and larger flywheel the H3.  Low reduction gearbox option on L3/H3. Center stand replaces rear stand. Hand shift lever passes through gate attached to side of petrol tank. 

1931

-

-

-

B31 replaces both L3 & H3. Chromium plated petrol tank with tartan panels. Twist grip throttle standard, lever throttle optional.

1932

FH****

35/C

RG/H****

Elimination of sump, oil carried in petrol tank compartment. Redesigned cylinders and aluminum plate style cylinder heads.  Flanged manifolds instead of gland nuts. Hand shift lever passes through knee grip which acts as gate.  Engine code assigned to enclosed flywheel design that may not have been marketed, no examples known. May have continued with EN prefix. Ditto frame code FH, may have used a FC prefix frame as per model A31, as catalog illustrations show them to be similar.

Models S5, S6, T6 and derivatives- 500/600/750cc SV, 1930-1933

1930

YF****

EQ****(500 & 600cc), EX****(750cc)

WG****, WG/T****S, WG/O****, GB/***(4-speed option)

Gearbox numbers and codes variable, frame numbers up to around 3200. Most Register machines are 1930/31.  Detachable plate style cylinder heads, inlet manifold cast integral with timing cover, ports on side of cylinders. All 82mm stroke with 62.25, 68, and 76mm bore. Center stand.  T6 had celluloid finish tank and foot boards, others were chromium plated tank and had foot rests. S5 was 500cc, S6 a 600cc. Single central front compression fork spring, lower links inside girder blades. 

1931

-

-

-

500cc now C31 model, 600cc E31 model with choice of foot boards or foot rests. All petrol tanks chromium plated with tartan panels. 

1932

-

-

-

No 500cc version. 600cc Sports now D32 or Greyhound and 600cc touring is E32 or Ayredale. Added 750cc touring model H32 or Mastif. Ayredale & Mastif continue to use old heavyweight duplex spring forks, though girders are slightly longer to suit larger section balloon tyres.

1933

-

6/E***(600cc), 75C***(750cc)

-

Factory production nil due to acute financial distress. Finned intake manifold, instrument panel sits atop petrol tank, metal tank badges. (Two examples known.) 600cc continues as D33/E33, 750cc as H33. 

Model DT5 500 OHV, 1931?

1931

?

OE****

YG****

Short-stoke version of DT, 68mm x 68mm, shorter wheelbase. 

Model A31, A32 - 350cc SV, 1931-1932

1931

FC****

EV****

RG/H****

Chromium plated petrol tank with tartan panel, hand shift lever passes through knee grip which acts as gate. Oil sight glass mounted on timing chest cover.

1932

-

EV****, 35/A***(plate heads)

-

Now called A32 or Terrier, possibly available with B32 plate style heads (not seen) when old style stock used up.

Model F31/G31 - 500/600cc OHV, 1931-1933

1931-33

FD*** (500cc), FG*** (600cc)

ET***(500cc), EU***(600cc)

AAG***(wide), ABG***(close), B/***(4-speed option 1932)

62.25mm (500cc) and 68mm (600cc) bore both with 82mm stroke. Frame numbers up to about 200, few made. Redesigned version of G28/F28 after one year absence. Saddle tank, chromium plate with tartan panels. Fully enclosed valve gear. Single carburetor inside airbox, flanged manifolds. Single compression spring front fork (same as DT/SW.) Center stand. Kick start lever now on gearbox. Catalogued as F32 & G32 in 1932, F33 & G33 in 1933 (1932 leftovers.)

Model C32 Bulldog - 500cc SV, 1932, under 224lbs

1932

FC****

5/A***

RG/H****

Lightweight 500cc based on B32. Detachable aluminum plate style heads.  Replaced 500cc C31 that was based on heavy-weight models.

Model K32/M32 - 350/500cc OHV, 1932

1932

FI***

35/D***(350cc), 5B***(500cc)

A***

Redesign of discontinued D29. Gearbox now mounted under saddle. Center stand. Chromium plated saddle tank with tartan panels. Pushrods on side of engine since it is based on the SV crankcase. Sparkplugs now on right.

Model X/X1 Bantam - 150cc 2-stroke, 1933-1935

1933

BA***

GY***, GYH***, GYN***

Albion

Horizontal Villiers single cylinder two-stroke engine, radial fins on cylinder.  Tubular struts above engine.  Sheet metal enclosure of engine bay.  With flywheel magneto lighting or with Lucas dynamo lighting. 

1934-35

FO***

15/A***(X1), 15/B***(X)

-

Douglas built copy of Villiers engine, axial fins on cylinder.  Pressed channel sheet metal strut above engine.  Catalogued Bantam as well as X with flywheel lighting and X1 with dynamo lighting.  1935 catalogued 5X and 5X1.

Model Y Comet - 250cc SV, 1934-1935

1934

FP***

25/A***

RG/H****

51mm x 60mm.  Redesigned cylinders with detachable plate style heads. Intake and exhaust manifolds now flanged instead of gland nuts. Chromium plated petrol tank with blue panels. Lightweight forks as per A32, or pressed sheet metal per Bantam. Rear carrier with leather toolboxes. Catalogued as model Y.

1935

FY***

25/B***

I/***

Saddle tank has more bulbous shape, black with blue panels.  Welded girder forks, large central barrel shape spring, lower headstock lug larger for taper roller bearing.  Single down tube frame divided into two tubes under engine.  Hand shift gate on side of petrol tank instead of through knee grip.  No rear carrier, cast aluminum toolbox on left. New cylinders and plate style heads.  Catalogued as 5Y and Comet.

Model Y1 Cotswold - 350 SV, 1934-1935

1934

?

35/E***

?

Continuation of the A32, but with chromium plated petrol tank with blue panels. Rear carrier with leather toolboxes. Catalogued as Y1. Probably continued with same prefix codes for frame and gearbox. 

1935

FY***

35/F***

I/***

Redesigned cylinders and heads, basically identical to 1935 250cc with larger cylinder bore. Catalogued as 5Y1 and Cotswold.

Model Y2 - 500 SV, 1934

1934

?

?

?

Continuation of the C32.  Probably continued with same prefix codes for frame and gearbox.  70 x 60mm  Otherwise similar to Cotswold and Comet. 

Model Z Wessex- 600 SV, 1934-1935

1934

FN***

6/F***

D/***(foot-change), E/***

Redesigned cylinders and heads on the D33/E33 crankcase, external geared oil pump. New single front down tube frame, trans mounts of continuation of engine rails. No sump, oil in petrol tank compartment. Saddle tank has more bulbous shape, with inset instrument panel, chromium plate with blue panels. Four speed gearbox in hand and foot shift versions. New heavy-weight lugged forks with lower links to outside and large central barrel shape spring. Catalogued as Z.

1935

FW***

-

J/***(hand-change), L/***  (foot-change), P/***(hand-change), Q/*** (foot-change)

Petrol tank finish now black, with blue panels.  Oddly, reverted to read stand with center stand optional.  Catalogued as 5Z and Wessex

Model Z1 Powerflow - 750cc SV, 1934-1935

1934

FM***

75/D***

D/***(foot-change), E/***

Redesigned cylinders and heads on the D33/E33 crankcase, external geared oil pump. New duplex front down tube frame, trans mounts of continuation of engine rails. No sump, so oil in petrol tank compartment. Saddle tank has more bulbous shape, with inset instrument panel. Four speed gearbox in hand and foot shift versions. New heavy-weight lugged forks with lower links to outside and large central barrel shape spring. Catalogued as Z1.

1935

 FX***

-

J/***(hand-change), L/***(foot-change), P/***(hand-change), Q/*** (foot-change)

Petrol tank finish now black, with blue panels. Oddly, reverted to read stand with center stand optional. Catalogued as 5Z1 and Powerflow.

Model OW/OW1 Speed Special - 500/600cc OHV, 1934-1935

1934

FR***

5/F***(500cc), 6/G***(600cc)

F/*** (hand-change), G/*** (foot-change)

Redesign of F/G models of 1932. Same cylinders, heads, and valve enclosure on new crankcase. No airbox. Single updraft Douglas barrel carburetor. Full duplex frame. Saddle tank has more bulbous shape, with inset instrument panel, chromium plate with blue panels. Four speed gearbox in hand and foot shift versions. Uses new heavy-weight front fork per Wessex/Powerflow. Catalogued as OW (500cc) or OW1 (600cc). Total production about twenty-five 1934-35.

1935

-

5/I***(500cc), 6/I***(600cc)

K/***(foot-change), O/***(hand-change), R/***(foot-change)

Petrol tank finish now black, with blue panels. Dual exhaust into cast alloy tubular silencers. Airbox returns, at least on 500cc. Douglas carburetor or updraft Amal (as used on S6). Rear portion of mudguard detachable. Catalogued additionally as Speed Special as well as OW/OW1.  A 750cc engine prefix 75/I assigned, but not catalogued.

Model Blue Chief - 500cc SV, 1935

1935

FZ***,

FV***(knock-out rear spindle)

5/H***

M/***(hand-change), N/***(foot-change)

New design engine of 68mm x 68mm, alloy cylinders and heads. Saddle tank has more bulbous shape, with inset instrument panel, chromium plate with blue panels. Uses new light-weight welded front fork per Comet/Cotswold. Catalogued as four-speed, but three-speed depicted! Probably three-speed only on early models designed for War Office, with knock-out rear spindle option (frame prefix FV/***, no known survivors) and this was used as catalog illustration. 

Model Endeavour - 500cc SV, 1935-1936

1935-36

AA***

5/J***

not applicable

Only pre-war transverse twin model manufactured. Used Blue Chief (Y2) engine turned sideways with unit construction gearbox, shaft drive. Impossible to mistake for any other model! Total production about one hundred 1935-36.

Model Aero - 250cc SV, 1936

1936

AD***

25/B***

?

Probably S/ prefix code gearbox. Three-speed. Reverted back to small petrol tank of 1932 models, painted black with blue panels. Engine same as Cotswold/Comet of 1935.

Model Aero - 350cc SV, 1936-1937

1936-37

AF***

35/F***

S/***

Same as 250cc except bore.

Model Aero - 500/600cc SV, 1936-1937

1936

AE****

5/L***(500cc), 6/L***(600cc), 6/M***(600cc)

M***, P/***, T/***

Continuation of the Blue Chief engine with cast iron cylinders and heads. 74mm bore added for the 600cc. Instrument panel gone. Foot-shift option is discontinued. Uses light-weight front fork of 250/350cc. 

1937

6/P***

6/P***

U****

Aero Tank transfer this year only. Douglas started stamping engine and frame with same prefix code. 500cc dropped.

1938

 6/Q***

 6/Q***

-

Oval tank transfer. Catalogued as DC/38. Allegedly last models used Web girder forks when supply of Douglas forks ran out. Leftovers sold into 1939. 

Model CL/38 - 150cc 2-Stroke, 1938

1938

 ?

 ?

Albion

Single cylinder vertical 2-stroke engine, copy of Villiers. Two port exhaust. Debatable if put in production, one replica recently built. 

Disclaimer

The information in these tables has been collected from various sources: factory records, registers of extant machines, Douglas publications, fellow enthusiasts, articles in the London Douglas Motor Cycle Club magazine the New ConRod, and personal knowledge.  While every effort has been made to provide the most accurate information available, the information provide above is offered as a guide only.  It is not recognized as official dating data by any licensing authority.    

Doug Cross, Doug Kephart, October 2004