CAMMY CHARMERS......................................

Real Classic - - What Lies Within - Pho­tos by Paul Miles

For a cou­ple of decades be­fore and af­ter the war, if you re­ally wanted to go fast then you needed an over­head cam. Paul Miles rides two black-and-gold beau­ties back to back, and dares to sug­gest which one is the bet­ter…

For a cou­ple of decades be­fore and af­ter the war, if you re­ally wanted to go fast then you needed an over­head cam. Paul Miles rides two black-and­gold beau­ties back to back, and dares to sug­gest which one is the bet­ter…

Many long sum­mers ago, as a novice rider, I sat lis­ten­ing to the grey­beards dis­cussing the rid­ing sen­sa­tion of a ‘cammy’ Nor­ton. At the time it seemed odd to sin­gle out a Nor­ton. Af­ter all, aren’t all four-strokes equipped with camshafts? Older (much) and wiser (…erm) I now un­der­stand they were re­fer­ring to a par­tic­u­lar type of Nor­ton sin­gle, the ohc In­ter­na­tional.

Why over­head cam? To win races, cammy en­gines rev higher and faster, mean­ing more power. They also cost far more to pro­duce, es­pe­cially back in the days of skilled labour work­ing on sim­ple ma­chin­ery. This ex­otic and ex­pen­sive de­sign ef­fec­tively pre­cluded the sale of ohc ma­chines to the gen­eral pub­lic, the lim­ited pro­duc­tion al­most en­tirely be­ing re­served for the rac­ing fra­ter­nity. Other man­u­fac­tur­ers also pro­duced ohc rac­ing sin­gles to dev­as­tat­ing ef­fect, no­tably Ve­lo­cette in the 350cc class. Where there’s a wal­let there’s a way, how­ever, and a small num­ber of ma­chines from each mar­que tricked onto the mar­ket and into the hands of the well-heeled en­thu­si­ast.

I was re­cently for­tu­nate enough to have fine ex­am­ples of both Ve­lo­cette and Nor­ton’s bevel-driven love­li­ness in my shed with the op­por­tu­nity to com­pare them – too de­li­cious a prospect to re­sist. Although dif­fer­ent in ca­pac­ity (one a 350, the other a 500) and year (with the Ve­lo­cette be­ing the last model pro­duced be­fore the war and the Nor­ton the first af­ter hos­til­i­ties had ended), they both ex­em­plify the ‘hand­built for sport­ing en­thu­si­asts’ ax­iom.


‘Win on Sun­day, sell on Mon­day’, the say­ing goes. No­body clung to it more than Ve­lo­cette and their rac­ing ma­chines were very suc­cess­ful, the 350 cammy sin­gle be­ing an es­pe­cially po­tent weapon. For road use, though, the fac­tory would rather your valves

were op­er­ated by pushrods. Ru­mour had it that Ve­loce Ltd lost money on ev­ery new ohc bike pro­duced for re­tail.

De­signed by Percy Goodman in 1924, the K (Kamshaft) mod­els were pow­er­ful and re­li­able rac­ers, with the over-the-counter KTT crowd­ing the grids at race­tracks around the world. TT win­ners in 1926, 28 and 29, their prow­ess was easy to spot. By 1936, the Mk2 ver­sion, in­clud­ing an all-al­loy en­gine with en­closed valves, was of­fered for sale. Avail­able in two forms, the KSS (su­per sports) had larger wheels and skin­nier mud­guards than the other­wise very sim­i­lar KTS (tour­ing sports).

The KTS you see on these pages emerged from the fac­tory in 1939 and the four-speed, 25bhp, 265lb ma­chine rests on 19” wheels pro­tected by heav­ily valanced mud­guards. The dif­fer­ences be­tween the two mod­els ef­fec­tively ended there. This ex­am­ple has only had three own­ers in its near 80-year life and has never been fully re­stored. Wear­ing its age as­ton­ish­ingly well, it looks ev­ery inch the quin­tes­sen­tial pre-war Bri­tish aris­to­crat. Qual­ity ex­udes from ev­ery cast­ing, the lines of the tin­ware and over­all fit and fin­ish. High end 1930s ma­chines ben­e­fit from the decades of skilled crafts­man­ship cou­pled with emerg­ing new tech­nolo­gies and a men­tal­ity where price is sec­ondary to prod­uct – some­thing we see the al­most to­tal in­ver­sion of in the post-war era. It was de­scribed to me as a ‘gen­tle­men’s ex­press’ and is, per­haps, the two-wheeled equiv­a­lent of a Bent­ley.

Start­ing a Ve­lo­cette is of­ten fraught with drama and I feared the worst, but, pro­vided the in­struc­tions were fol­lowed to the let­ter, the nar­row-crank­case cammy fired up first kick vir­tu­ally ev­ery time, set­tling quickly into a rock-steady idle. The al­most-too-quiet en­gine rustling its camshaft, off­set by the gen­tle chuff from the fish­tail, the KTS seemed too, well, nice, to be con­sid­ered a road­go­ing racer.

The four-speed, pos­i­tive-stop gear­box, an­other Ve­lo­cette first, proved be­yond crit­i­cism, as was the fault­less clutch. The trou­ble­some na­ture of post-war Velo clutches re­flects, per­haps, the com­pany’s chang­ing at­ti­tudes to­wards profit, rather than in­nate poor de­sign.

The KTS’s per­for­mance was bright, with power build­ing steadily and the en­gine feel­ing un­flus­tered. Gear ra­tios were well spaced al­low­ing it to quickly reach its nat­u­ral cruis­ing speed of… 55mph. The han­dling and brakes were as good as al­most any­thing I’ve rid­den from the era and com­ple­mented the per­for­mance per­fectly.

Ut­terly de­light­ful to ride, gen­tly chuff­ing around the Dorset lanes, feel­ing un­break­able and re­lax­ing to ride, it was hard to be­lieve this so­phis­ti­cated sin­gle, al­beit one of rel­a­tively mod­est ca­pac­ity, could in the right hands be a po­tent rac­ing weapon, ca­pa­ble of be­ing hurled around the TT course. And yet, the ro­bust­ness Ve­lo­cette had en­gi­neered into their ohc ma­chines meant pre­cisely that, with the cammy en­gine re­li­ably de­liv­er­ing what­ever per­for­mance it had all day long. To fin­ish first, one must first fin­ish and all that.

I have lit­tle doubt the KTS would have steadily mo­tored me to John O’Groats with­out com­plaint or spe­cial prepa­ra­tion, it was that good. But it would pre­fer to do so at 50mph, with the 80mph top speed be­ing re­served for spe­cial oc­ca­sions only.


Nor­ton’s ohc en­gine, like the Ve­lo­cette, also orig­i­nated in the roar­ing Twen­ties with the CS1, although the ex­posed hair­spring valve In­ter­na­tional model first ap­peared in 1931. Tech­ni­cally avail­able as a road­go­ing ma­chine, the In­ter was re­ally the pre­serve of rac­ers, both fac­tory spon­sored and pri­va­teers, with rid­ers like Stan­ley Woods and Jim­mie Guthrie be­com­ing house­hold names in the era. Fac­tory rac­ing spec­i­fi­ca­tion didn’t re­ally fil­ter into the road ma­chines as so few were ac­tu­ally pur­chased as pure road­go­ing mo­tor­cy­cles, but by 1938 the racer could spec­ify plunger rear sus­pen­sion, the new Road­holder tele­scopic forks and an all al­loy en­gine – pro­vid­ing he knew the right peo­ple to ask.

So fast and rugged was the In­ter that Model 30s were is­sued to the mil­i­tary po­lice, un­der the con­trol of Sir Mal­colm Campbell, for fast pro­tec­tion of the Royal fam­ily should they need ur­gent evac­u­a­tion in the event of a Ger­man in­va­sion.

WW2 ended pro­duc­tion of course and it wasn’t un­til 1947, the model year of this ma­chine, that ohc pro­duc­tion fi­nally re­sumed. Avail­able in two ca­pac­i­ties, 350cc (M40) and 500cc (M30) Nor­ton had fi­nally be­gun to stan­dard­ise spec­i­fi­ca­tions. All ma­chines now came equipped with the ‘gar­den gate’ plunger frame and long Road­holder forks. The en­gine was only avail­able in iron head and bar­rel form, and a close ra­tio gear­box was sup­plied as stan­dard.

The Model 30 500cc ma­chine on these pages is an older restora­tion. Like most other In­ters it has some rac­ing his­tory, and was en­tered for the 1947 IoM TT. Re­stored to road spec­i­fi­ca­tions around 30 years ago it is fairly rep­re­sen­ta­tive of an ex-fac­tory road ma­chine, although some of the con­trols are pat­tern. The 29.5bhp Nor­ton

Above: Ve­lo­cette’s camshaft sin­gle, seen here in road-go­ing KTS form, ap­par­ently the TS stands for Tour­ing Sports. Seems fair Left: Ve­loce cer­tainly un­der­stood who rode their mo­tor­cy­cles!

Velo’s 1939 brochure re­veals that the en­gine could be sup­plied ei­ther a with a com­pres­sion ra­tio of 7.5:1, mak­ing it suit­able for ‘ethyl spirit’, or 8.4:1, suit­able for a 50% petrol / ben­zol mix­ture. Times change

And here’s how that en­gine works. It all looks sim­ple to 21st cen­tury eyes, but mak­ing these rel­a­tively com­plex ma­chines work re­li­ably in the 1930s was not easy at all

The en­gine, most def­i­nitely the ma­jor sell­ing point of ohc ma­chines in those dis­tant days

Velo’s ohc sin­gles used es­sen­tially the same trans­mis­sion ar­range­ments as the ohv ma­chines. The pri­mary chain runs in­board of the clutch, and the front chain­case ex­ten­sion con­tains a belt drive to a Miller dy­namo, which in turn has its volt­age con­trol...

No shot of a Velo sin­gle – any Velo sin­gle! – is com­plete with­out the fish­tail

View from Velo heaven, re­veals the sport­ingly bare han­dle­bar lay­out, and the top links of the girder forks

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