Prewar Douglas 2-3/4 motorcycles – Dating information Engine, Frame, Gearbox numbers

Prewar Douglas motorcycles – Dating information with Engine, Frame and Gearbox numbers for the 2-3/4 h.p. 349cc horizontally opposed twin from 1907 to 1926.

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Year Frame # Engine # Gearbox # / letters Distinguishing features for the year / model
1907 101 – 128 101 – 128 No gearbox Diamond frame, stirrup front brake, belt rim rear brake, dry cell and trembler coil ignition, atmospheric inlet, direct belt drive to rear wheel (single speed), pedal gear, and reinforced bicycle front fork. 60mm bore x 60mm stoke for 340cc. Gland nuts on copper tube inlet manifold. Cylinder threads into crankcase. Front suspension of bicycle blade forks on swing links. Twenty-seven machines built, of which twenty-four sold.
1908 129 – 159 129 – 159 No gearbox Ignition now by magneto with exposed drive gear. Recess in the petrol tank to clear magneto. Production variously reported as 30 to 50 machines, with the later perhaps being cumulative.
1909 160 – 441 160 – 441 No gearbox Model B. Engine sits four inches lower in the semi-diamond frame, saddle and overall height drops two inches, and the wheelbase increases. Headstock is braced with a diagonal tube. Druid front forks with compression springs. Rear wheel stand provided. First use of the signature silver and blue tank motif. Model A (1908 model) still offered, though it is not known if this designation was used in 1907-08. It was probably created with the advent of the Models B, since trade advertisements in 1907-08 do not use the term Model A (and only the one model was offered at that time.) This is the earliest date I have seen catalog information for.
1910 442 – 1464 442 – 1464 No gearbox Model C. Proper light motorcycle extension sprung front forks, cradle frame, petrol tank not as deep. Tank sides faceted at front and rear where it narrows to meet the frame. Braced headstock. Two horizontal frame tubes below engine, one above the other. Lower rear fork joins saddle post at very bottom, in line with housing for pedaling gear. Single bolt into port securing each end of cast aluminum inlet manifold (no gland nut.) Cylinders now mount to crankcase with two studs. Light shield over external magneto gear drive. The engine pulley is now adjustable, and the rear belt rim perforated to save weight. Model B (1909) still cataloged.
1911 1465 – 3999 1465 – 3999 101 – ? when fitted Model D (née Model C) still direct belt drive, though the frame had provision for a two-speed gear (under test in road trials in 1910) mounted below the engine as an optional extra through factory or dealer installation. Customer’s 1909 and 1910 frames could be altered at the factory to accept the 2-speed option. Petrol tank wider and sides curve gracefully inward at front and rear. Lower rear fork meets saddle post midway between two lower frame members, housing for pedal gear is below the level of the lower tube. Model E, new frame with single frame tube below engine. Engine lower, no notch in petrol tank to clear magneto. Lower rear fork horizontal and joins saddle post slightly above engine rail. Chain to two-speed countershaft under rear cylinder, thence belt to rear wheel. Clutch and hand starting an option, No pedaling gear. Footboards fitted. Model F, 2-speed, clutch, hand start, open frame ladies model.
1912 4000 – 7100 4000 – 7100 Model G, chain to (single-speed) countershaft, foot pegs. Model H, 2-speed, with foot boards. Model J, 2-speed with foot pegs and option of drop handlebars. Model K, 2-speed with clutch and kick start. All with lower frame, single frame tube below engine which lines up with lower rear fork. Addition of a diagonal tube brace between saddle post and lower rear fork. Petrol tank and top frame tube slopes down at rear to accommodate lower saddle position. Countershaft unit moves rearward to base of saddle post, engine has mechanically operated inlet, fully encased internal magneto drive. Only Model G retains pedaling gear, now fitted to countershaft unit. Model L, specs as K, but ladies model with open frame.
1913 6940 – 12500 Appox 6940 – 12500 Appox Models N, O, P, R respectively, ladies Model S. Return to curved inlet manifold with gland nuts, engine bore enlarged to 61mm for 349cc, stroke still 60mm. Unexplained overlap in numbers with prior year. Rear luggage carrier on back mudguard became standard. Model N (single-speed) last model offered with pedaling gear.
1914 12434 – 19000 12434 – 19000 Models renamed T, U, V, W respectively, ladies Model X. Exhaust pipes enter silencer under engine tangentially, for a spiral flow effect. Switch to American Dixie magnetos when supplies of Bosh interrupted by hostilities. Last year single-speed offered.
1915 19500 – 29300 19500 – 29300 Model designations retained from 1914. Rear stand pivots at a brazed-on dedicated lug, rather than a hole through the rear fork tube. 3-speed gearbox available on some models. Model WD (War Department), large mud shield at front of frame, no clutch. Last year for Ladies model. Cork plate clutch vs. cone, where fitted.
1916 27152 – 32428 27152 – 32428 Model U (foot boards) and Model V (foot pegs) both with either 2 or 3-speed. Model W, 3-speed and clutch. Model X still ladies model now with 3-speed and clutch. All models, new front fork, shackles are now inboard of girders, which has the leading tube straight and the trailing tube curved. Valve guides are now removable from cylinder. Addition of Model WS, specs as W with swing arm rear fork, suspension by cantilevered leaf springs. Not believed to have gone into production. Wartime production for civilian use much reduced.
1917 32429 – 36178 32429 – 36178 Civilian production ceased February for duration of the war.
1918 36179 – 39257 36179 – 39257 Military models U,V,W with 2 or 3 speed gearboxes, optional clutch on 3-speed box. Many in khaki finish.
1919 39257 – 42958 39257 – 42958 G2(2-speed), G3(3-speed) British-made EIC magneto. No diagonal tube bracing headstock to top frame member. (Surplus braced headstock frames used into early twenties.) 1919 catalog literature suggests only a 3-speed was to be offered, but this must have changed and also there were many reconditioned ex-military 2-speeds sold by the factory. Mid-year an improved cork plate clutch of six plates, compressed by pressure plate and three toggle arms.
1920 42959 – 48200 42959 – 48200 G2(2-speed), G3(3-speed), G6(W20),G8(W20, 3-speed w/clutch) Engine 60.8x60mm, 348cc. Models WD and W20. Stronger welded lug front forks, Ferrodo clutch lining. (Surplus ‘veteran’ forks used into early twenties to deplete old stock.)
1921 48201 – 51800 48201 – 51800 LG(WD),CG(W21), HG, IG, KG, Models WD and W21. Cork clutch reduced to four plates.
1922 51801 – 55370 51801 – 55370 LG(WD),CG(W21), HG, IG, KG, 2-speed. 3-speed with clutch.
1923 55371-64200 55371-64200 LG(WD),CG(W21), HG, IG, KG, Model TS, 2-speed. Model W, 3-speed with clutch and kick start, Model 3SC, 3-speed all chain drive, fitted with small diameter inverted v-wedge brakes from OHV model. Cooling fins on inlet ports.
1924 *****(TS, SW), CF101-1350(CW) 64201-74500 LG(TS), NG(2-speed), OG(3-speed) Model TS as before. Model SW, 2-speed with flywheel clutch. Model CW, 3-speed all chain drive with flywheel clutch, dummy belt rim brakes (about half rim diameter) front and rear. CW frame numbering starts at 101, but engine numbers continue in series with TS and SW.
1925 *****(TS), CF1350-8000(CW) 74501-84200 LG(TS),OG(CW) TS25, CW25 as before.
1926 *****(TS), CF8000-17529(CW) 84201-86791 LG(TS), A/OG(CW) Model TS26 as before. CW26 with shock absorber in gearbox sprocket. CW just reaches frame numbers of five digits. Last year for venerable 2-3/4hp, though a timing cover engraved for 1927 has been seen. Last year for belt drive, clutch-less, 2-speed with stirrup front brake (the TS)!  Discontinued when stocks exhausted in favour of new 350cc Model EW, introduced late 1925



Notes on the table information.

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

Minor discrepancies: You will see that up-to about 1916, there are occasions when the engine / frame numbers overlap. The information on this page has been carefully researched by people much more capable than me. They used a variety of reputable sources. However, this is the best guide that I know of. So, use it as a “guide”.

Credit: Thanks to Doug “K” for his kind permission to reproduce this hard work that he and Doug “C’ compiled many years back. It is reproduced on this page with his permission and the acknowledgement of The Douglas Forum.



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Disclaimer: The information supplied here is a guide. It’s pretty accurate, but should be used as a guide only.