Most motorcycle manufacturers’ frames were understandably intended to fit round specific engines, but the Cotton’s was designed purely to achieve stiffness. This had both advantages and drawbacks as the same frame could be used for a range of models, but specific mounts had to be devised for each new power unit. This was normally no problem, as the engine/gearbox assembly was effectively suspended from the headstock and saddle tube, with the gearbox braced to the rear wheel spindle. However, the new OHV Blackburne unit was simply too tall to sit beneath the frame, and while lesser men might have immediately changed the shape of the chassis, Bill Cotton simply tilted the engine forward until it fitted! Whether this encouraged other manufacturers to go down the ‘sloper’ route that became so fashionable in the following few years, we’ll never know, but the result certainly looked spot on, with the engine’s angle matching that of the front down tube.
Bill Cotton later compromised slightly on this aspect, and used a revised steering head casting that maintained strength, while splaying the front of the tubes out enough to accommodate the head of an upright cylinder. I suspect that this was done more for convenience’s sake than for styling reasons, because you only have to glance at the Miller Museum’s sloper to see that the tilt of its engine severely complicated access to the carburettor, and the new frame’s wider front end had the unwanted side effect of further increasing an already excessive turning circle.
The use of a saddle-style petrol tank – a change that occurred around the time this machine was made – has the same effect. And before experts rush to tell us what is and isn’t right for a late-Vintage Cotton, I must detail a curious set of circumstances that led Sammy Miller to be well aware that this particular motorcycle may well have originally featured the earlier type of tank that fitted between the frame tubes.
The machine came into his hands from the same local source as the racing Cotton that we featured in TCM October 2005, and for a long time Sammy knew nothing of its history. So when it came to the top of the list for restoration he did the obvious thing, and started looking at period sales literature to check on the original appearance of stock Cotton-Blackburnes.
“It seemed to be a 1929/30 Model 25 OHV Super de Luxe,” he tells me, “but one feature didn’t match up, and that was the design of the gear lever. The reference information showed a long lever pivoted near the back of the tank, while this bike’s lever was short and mounted at the front. I’d just about got the hacksaw in my hands ready to saw the pivot off and re-position it, when somebody passed me some old photographs (see one of the photos inset on the opening spread). Glancing through them, I was astonished to see a small-tank competition Cotton-Blackburne with a short, forward-mounted, gearlever, just like this one. And when I looked closer, there were other similarities between the bike in the photo and the Museum’s project. For instance, its front brake plate is set into the drum, which contrasts with the overlapping one fitted to standard Cottons of the period. Additionally, the Museum’s Cotton had been locally owned for years and one of the pictures had a nearby address scrawled on it, so all in all I was convinced that I’d got hold of the same bike, and decided to continue restoring it in the style shown in the photographs.
“A name that looks like ‘Les Harthorn’ is scribbled on the back of the photos,” Sam continues, “so he was presumably the owner or rider at the time, while the name above the local address is MK Field, and I guess he was a subsequent owner. Naturally, we’ve been round to 16 Merryfield Close, Bransgore, but the house has been demolished and built over, so the trail has gone cold, but if anybody knew either of these chaps or anything about them or their bike, I’d be delighted to learn more.”
As it happens, the gear lever on the restored Cotton is inverted compared with the photos, but nobody expects competition bikes to remain in exactly the same trim for long. More importantly, another of the pictures shows the same – but obviously older – Les Harthorn with the racing Cotton-Blackburne we tested previously, so he was obviously devoted both to the marque and to competition, and it seems more than likely that Sammy’s hypothesis is correct.
The sort of detail Sammy would like cleared up is whether the Cotton was raced on or off-road. It’s certainly posed on a grass surface for the photographs, but that could simply have been for convenience’s sake. Whatever he did, Les Harthorn was obviously a serious competitor with smart leathers, boots and helmet – no second-hand roll-neck jerseys and jodhpurs for him!
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