Patrick,
The machine in question ought to be in reasonable condition. It was shipped over to the UK in 1992 and refurbished by Bendix Ltd, successors at the Douglas factory site in Kingswood. It had been kept in very presentable condition up until that time, as pictures of it being removed from its crate on arrival in the UK show. At some point since its round the world journey it had been painted overall a light color. Robert E. Fulton Jr. collected the machine in 1993 at the former works site, so completing the final USA-UK leg of his journey some sixty years on. Not sure exactly what Bendix did in the way of refurbishment mechanically; though it is clear it got re-painted at that time a darker color, all black perhaps. Originally it would have been black, with chromium plated petrol tank with the Douglas tartan transfer side panels used during that period.
It seems to be a 1932 “Greyhound” designation D32 which listed the (generally an option) four-speed gearbox as standard (though a Douglas catalog picture mistakenly shows the three-speed!) which also had the side draft carburetor as shown in the book “One Man Caravan”. There was another 600cc that year, an “Ayredale”, but it had an updraft carburetor as used the previous year and the standard three-speed gearbox. A distinctive feature is the cylinder heads on Fulton’s bike. The spark plugs are on the side and not the top as typical with this series engine, also they are strutted between the fins. These heads never appeared in any of the catalog literature to my knowledge, and I suspect they might have been from a Douglas industrial engine of the same year (which were based very much on the motorcycle engine.) It might be they offered a lower compression ratio that was felt to be advantageous for the journey.
However T6 model would not be far off, S5,S6,T6, D31, E31, D32, E32, H32 (500-750cc) they are pretty much all the same. The principles of the engine are normal, but the construction is a little unorthodox. For instance the threads for the valve adjustment are on the valve stems rather than the tappets. Rather than the simple and direct flat tappets of the preceding models, it used a system of pivoting roller tappets favored by the factory chief designer at time, Freddie Dixon. The rocking links are sheet metal strap like affairs, and not very robust. They tend to cut slots in the pivot pins and the holes get enlarged in the straps. In time the rollers can stop rolling, develop flats, and just skid over the cam. Apparently the effects of which on performance are not very noticeable! All simple stuff and easy to refurbish or re-make. Afterwards they went back to the direct flat tappet design for all subsequent side valve models. Reprints of the handbook and the spares list are available from Jack Withers in Australia.
The only other quirky aspects are the servo band brakes. You come across really effective and really ineffective examples of these; seemingly care in rebuilding makes no difference to the outcome folks claim! The other weak point are the wheel axles, Douglas always had light axles of high nickel steel. But these still bend in time, ruining the obsolete size taper roller bearings that were fitted. Wheel bearing races need to be checked for signs of breaking up of the race surface. The hubs can be converted to sealed ball race, but some precision machine work is involved.
The flywheel clutch might be a bit strange to the average motorcyclist. But most Dougies had them from 1925 onward, so they are considered normal to the breed. Play in the carrier bearing sleeve that translates on the flywheel hub can cause the clutch to drag abominably. Also the race inside the flywheel sprocket will break up after high mileages. However this was more of a problem on the o.h.v. machines fitted in addition with a pressure plate. Less room for lift and more power to cope with.
Some of the thread sizes might be found to be a bit quirky, even for the British. Douglas had many special thread sizes from the vetran era, a few of which persisted into the mid-thirties. 7/23-33 and 17/64-25 spring to mind.
The S6 series (as all these tend to be colloquially known) are said to make nice sidecar tugs. Indeed Fulton started out with a Douglas sidecar fitted, but it was wrecked and abandoned in France almost immediately. I do not think any mention of it appeared in the book.
"One Man Caravan" was printed in London (1936?) and in New York (1937), second hand copies still turn up. Also it was reprinted circa 1996 in paperback edition. ISBN 1884313051.
-Doug
