For a while, the plunger cammy Nor­ton fell out of favour with fast lads who pre­ferred the feath­erbed frame. But Rowena Hosea­son reck­ons that any 500 sin­gle which will take you to the ton is worth a sec­ond chance…

For a while, the plunger cammy Nor­ton fell out of favour with fast lads who pre­ferred the feath­erbed frame. But Rowena Hosea­son reck­ons that any 500 sin­gle which will take you to the ton is worth a sec­ond chance…

Real Classic - - What Lies Within - Pho­tos by Kay Eldridge of Fo­cusedI­, Rowan Bond, Mor­tons ar­chive and Bon­hams auc­tion­eers

When peo­ple talk about Nor­ton’s cammy sin­gles they typ­i­cally men­tion the Manx first and the In­ter­na­tional… well, even­tu­ally, maybe, as a bit of an af­ter­thought. Hardly fair, see­ing as the In­ter­na­tional came first and the Manx model popped up post-war. The In­ter was the 1930s race-bred road­ster equiv­a­lent of the works over­head cam com­peti­tors.

Joe Craig and Arthur Car­roll drew up the new Nor­ton cammy en­gine for the 1930 sea­son, to cure some of the ground­break­ing CS1’s idio­syn­cra­sies. The CS1 was an im­pres­sive en­gine, but it was tech­ni­cally tricky to keep in tune and rid­ers found it tough to ex­tract its peak per­for­mance. The In­ter was a smaller ma­chine over­all, with a shorter wheel­base and lower rid­ing po­si­tion which favoured the vin­tage style of ‘lean out’ cor­ner­ing, knees grip­ping the tank to stay in the sad­dle.

The new model paved the way for the cammy Nor­ton to be­come a club­man’s racer rather than a pure works ma­chine – it was per­fectly pos­si­ble for In­ter own­ers to swap a valve or a pis­ton with­out an en­tire team of me­chan­ics. In­evitably the boys of Brace­bridge Street of­fered pri­vate cus­tomers the op­tion to up­grade their In­ters with all man­ner of com­pe­ti­tion-spec com­po­nents. In the mid- 1930s you could spec­ify an In­ter in ‘Manx GP’ trim, bristling with op­tional ex­tras. Af­ter WW2, things be­came clearer with the launch of the cus­tomer dou­ble-knocker Manx model in 1949, while the In­ter stayed avail­able with its sohc top end. That doesn’t stop to­day’s sell­ers mis­de­scrib­ing an over­priced cammy sin­gle as a Manx when it is in fact an In­ter, of course…


Even among the ac­tual In­ter­na­tion­als, there’s a clear de­mar­ca­tion of de­sir­able in­car­na­tions. Most folk feel that the truly un­ap­proach­able Nor­ton is equipped with a feath­erbed frame, so the 1953-on­wards ver­sion of the In­ter, with all-al­loy en­gine and laid-down gear­box, is usu­ally the one which hogs the lime­light. At the other end of the spec­trum lies the sim­plic­ity of the In­ter’s orig­i­nal it­er­a­tion with rigid rear end and girder forks; a gen­uinely vin­tage ex­pe­ri­ence from the 1930s. The fi­nal feath­erbed In­ters might be the most pow­er­ful of the bunch and are blessed with the best han­dling of their era, but the early In­ters are pretty frisky when the en­gine comes on song. Both types sell for se­ri­ously big bucks.

Then there’s the awk­ward in­terim model. The In­ter was rein­tro­duced af­ter WW2 for the 1947 Club­man’s TT, where both 350 and 500 took top hon­ours. This bike was lit­tle more than a re­freshed ver­sion of the pre-war racer, but the cus­tomer ma­chine which fol­lowed for 1949 was a more prag­matic propo­si­tion. For the first time, the pub­lic was of­fered a cammy en­gine in a chas­sis with sus­pen­sion at both ends – but the ‘gar­den gate’ frame with tele forks and plunger sus­pen­sion did not meet with uni­ver­sal ap­proval…

The pre-war rigid bikes’ short wheel­base and low cen­tre of grav­ity gave them re­spon­sive han­dling and in­stinc­tive steer­ing. ‘Plunger sus­pen­sion,’ ob­served Don Mor­ley, who owned sev­eral In­ters over the years, ‘es­pe­cially if com­bined with tele forks, raises this level, adding con­sid­er­ably to the over­all weight to ruin the en­tire equa­tion. In­deed, these In­ters suf­fer from stodgy and de­cid­edly un­sport­ing han­dling.’ He thought the 1949 in­car­na­tion of the In­ter was ‘beau­ti­ful-look­ing but ul­tra-heavy and evil-han­dling.’

His­to­rian Roy Ba­con agreed. He thought the post-war In­ter was ‘won­der­ful to look at’, but ‘it was no road ma­chine. It rat­tled, it leaked oil and the cam tim­ing bat­tled with the si­lencer to hold the road per­for­mance down to around 85mph for the 500. The 350 was slower, hav­ing to drag along vir­tu­ally the same weight, and thus its ac­cel­er­a­tion suf­fered badly.’

Even so, if you fit­ted a free-breath­ing pipe, then ‘a good 500 could make a mem­o­rable ex­pe­ri­ence.’ Fit­ted with a Brook­lands can, a plunger-framed 500 in a pre-war state of tune was timed at 97mph, and Ba­con reck­oned that ‘the en­gine, cou­pled to a close-ra­tio gear­box, had deep-down stamina. The plunger frame called for a firm hand and could roll at higher speeds, but would al­ways work with a rider to keep him out of trou­ble and get him through a corner.’

Fast rid­ers cer­tainly could make the most of the rac­ing ver­sion of Nor­ton’s plunger frame. ‘It made the bikes much more com­fort­able to ride in long races like the TT,’ ac­cord­ing to the firm’s works rider Fred­die Frith. And in­deed, Frith clocked the first ever 90mph lap of the TT cir­cuit in 1937 on a cammy sin­gle in a pre­pro­duc­tion plunger frame. How­ever, as Jim Reynolds once ob­served, ‘ac­tion pictures of the time sug­gest a very phys­i­cal high-speed wrestling match!’

These opin­ions ex­plain why the plunger In­ters have tra­di­tion­ally been less soughtafter than their sib­lings, and why their val­ues haven’t risen quite so strato­spher­i­cally. Although the Model 30 (490cc) and Model 40 (348cc) were the top of Nor­ton’s range for 1949, those times were pretty tough. Gone were the glo­ri­ously high com­pres­sion ra­tios of the late 1930s, when works rac­ers ran 12:1 on ex­otic fu­els – the 1949 In­ters were fit­ted with com­pres­sion plates to cope with poor qual­ity, 72-oc­tane pool petrol.

While the works bikes were still gussied up with trick bits, the road-go­ing In­ter spec­i­fi­ca­tion was a bit less spe­cial than it used to be and shared many more com­po­nents with the ohv road­sters. The sohc iron en­gine

re­tained its ribbed crank­case with built-up crankshaft, du­plex gear oil pump, ex­posed hair­pin valve springs sur­rounded by oil feeds, ad­justers and breathers, with petrol pro­vided via a TT carb.

A three-spring multi-plate clutch trans­mit­ted drive to Nor­ton’s four-speed pos­i­tive-stop gear­box, now con­verted to foot change. The chain-drive mag­dyno was mounted be­hind the cylin­der, ahead of the hand­some, wrap­around oil tank. The petrol tank lost its de­li­cious scal­loped edges but kept the cut­away to ac­com­mo­date the carb.

The gar­den gate frame is sim­i­lar to the one used on the ohv ES2 sin­gle, adapted to suit the cammy en­gine and fuel/oil tanks. While the Road­holder forks at the front end were an un­doubted im­prove­ment over Nor­ton’s Webb-type gird­ers, the In­ter lost its light­weight pre-war mud­guards and was weighed down with a set of stan­dard guards. The In­ter was given dif­fer­ent tyres to the ES2, and swapped from a 3.25 rear sec­tion to 3.50 for 1951.

Although the road­tests of the time over­flow with gush­ing ap­pre­ci­a­tion of the post-war plunger In­ter, you can tell that it was a tricky crea­ture to tame. ‘A trace of clutch drag made low speed gear chang­ing slightly heavy,’ said

The Mo­tor Cy­cle, ‘and it was not usual to ob­tain an ab­so­lutely clean change from bot­tom to sec­ond gears.’ They felt that the 32-inch sad­dle was pretty high, while the 29-inch wide han­dle­bars were un­usu­ally wide.

Although this gave it ‘the feel of a big ma­chine,’ the In­ter was con­sid­ered ex­tremely agile, and its brak­ing was flat-out fab­u­lous: 25ft from 30mph is im­pres­sive by any stan­dard. Mo­tor Cy­cling noted that the rear spring­ing felt quite hard in ac­tion, but cer­tainly aided sta­bil­ity: ‘road-menders’ vi­cious cross-gul­lies could be tack­led with­out gri­peas­ing.’ Both pub­li­ca­tions sug­gested that the In­ter was suited only to ex­pe­ri­enced, hard rid­ers – and Mo­tor Cy­cling had the de­cency to note that their bike was equipped with a spe­cial si­lencer: the cus­tomer ma­chine would be qui­eter and some­what… slower.

The rein­tro­duced In­ter had cer­tainly lost some of the pre-war model’s sparkle, but it was only in­tended to be a stop-gap, while Joe Craig and his gang got to grips with the Manx mo­tor and an all-al­loy sohc en­gine which would slot into the feath­erbed frame from 1953. Even so, some tech­ni­cal trick­ery kept the plunger In­ter com­pet­i­tive on the Is­land, where it claimed three wins in 1949, 1950 and 1951 in the Se­nior Club­man’s TT.

The plunger In­ter was also a prac­ti­cal propo­si­tion for the man (or wo­man) in the street. Be­fore WW2, in­trepid trav­eller Theresa Wal­lach se­cured her gold star at Brook­lands on a 350 In­ter, lap­ping at over 100mph. Yes, I did type that right. A 350. At 101.64mph. OK, so Wal­lach chose her mo­tor­cy­cle wisely – the bike was hired (for £5) from le­gendary tuner Fran­cis Beart – but her achieve­ment is all the more mighty when you con­sider that it lashed down with rain that day…

The post-war ver­sion might not’ve been up to match­ing that feat, but in­stead a tele / plunger In­ter car­ried Wal­lach on an epic ad­ven­ture across Amer­ica. For nearly three years, she worked her away around the USA, Mex­ico and Canada, main­tain­ing her ma­chine as she clocked up over 30,000 miles.

So take heart if you quake at the idea of set­ting up the In­ter’s top end, with its cam driven via that hand­some two-piece bevel shaft and an Old­ham cou­pling. Don Mor­ley sug­gested that any rea­son­ably com­pe­tent span­ner­man shouldn’t feel too in­tim­i­dated by the In­ter en­gine. It ‘need hold no great ter­rors,

for they are re­mark­ably sim­ple,’ he said.

Mor­ley found the In­ter mo­tor to be much the same as Nor­ton’s ohv sin­gles ‘with a few ex­tra but mi­nor com­pli­ca­tions, like a need to shim the up­per and lower bevel gears to ob­tain per­fect mesh. There is lit­tle to worry about, given a source of shims, some com­mon sense and a mod­icum of pa­tience which are all needed for as­sem­bling, dis­man­tling and re­assem­bling the bevel gear hous­ings as of­ten as it takes un­til the clear­ances are right.’

The main thing with the cammy mo­tor is get­ting to know it, so you can pre­vent any lit­tle is­sues de­vel­op­ing into ma­jor ag­gra­va­tions. For in­stance, the small­diam­e­ter feed to the valve guides – es­pe­cially on the ex­haust side – can get choked with cacar­ Modern­ode rid­er­s­des may also want to con­sider care­fully the mer­its m of the race­ori­ented close-ra­tio gea ar­box which fea­tures a vast gap be­tween firs t and sec­ond. Don Mor­ley reck­oned that the 500’s ‘won­der­fully free-revving’ en­gin e with its ‘oo­dles of us­able torque’ works w bet­ter with a wider-spaced gea ar set from an ES2: ‘less of a pain to use o n to­day’s roads.’

And there is ev­ery chance that if you buy a plunger In­ter you will end up rid­ing it – this is an­other mo­tor­cy­cle which has found more favour as a clas­sic than it did dur­ing its ini­tial out­ing. It may be heav­ier and slightly slower than the fly­weight pre-war ma­chines, but the Road­holder forks and seven-inch stop­per are much more suited to 21st cen­tury traf­fic than 1930s gird­ers. You could re­move the com­pres­sion plate and give the per­for­mance a bit of a bump… or leave it in situ and en­joy kick­ing over a big sin­gle with­out it snap­ping at your an­kle.

Like­wise, the plunger In­ter is both lower and slim­mer than the feath­erbed which fol­lowed it. (Nor is the feath­erbed frame of the In­ter­na­tional quite the same as the one with which the twin-cam Manx was equipped). If you want an ex­otic Nor­ton which is beau­ti­fully bal­anced and easy to ma­noeu­vre at low speeds – but which won’t shat­ter your spine as you rum­ble over ev­ery road ridge – then the gar­den gate va­ri­ety has an aw­ful lot go­ing for it.


Rowan Bond in Aus­tralia didn’t need too much con­vinc­ing. He fell in love with cammy Nor­tons while watch­ing them race in the 1970s, so when the op­por­tu­nity arose to se­cure (most of ) one in 1983 he snapped it up. His 1949 Model 30 was in­com­plete and very rusty. ‘I found the rolling chas­sis and gear­box on a dump; the en­gine had been used in a speedway car.’ As­sem­bling an ac­tual mo­tor­cy­cle in­volved sourc­ing the miss­ing com­po­nents, re­plac­ing the ones which were be­yond re­cov­ery, and build­ing up the re­sult­ing jig­saw puz­zle – and it took a while be­fore Rowan could re­ally get to grips with the project. Over seven years be­tween 1993 and 2000, Rowan did the ma­jor­ity of the work him­self, call­ing in ex­pert as­sis­tance for cru­cial tasks.

‘My frame was bro­ken so the front down­tube was sleeved and pinned. The frame was quite hor­ri­bly bent out of shape from ly­ing in the dump with things tossed on top of it, so there was quite a bit of work straight­en­ing it for use. While it’s not in the feath­erbed class of han­dling, it does han­dle and ride very well. The In­ter sprung heel is, I be­lieve, much bet­ter than the same fit­ted to the ES2, due to the dif­fer­ent di­men­sions. The sus­pen­sion is much more com­pli­ant and the chain ten­sion is main­tained much bet­ter.

‘When I built my mo­tor, I was as­sisted by an old friend who’s now un­for­tu­nately no longer with us. Garth was quite a whiz with bevel bikes, es­pe­cially Du­catis and Nor­tons. He was quite ex­pe­ri­enced at putting them to­gether, even though he used to make jokes about emp­ty­ing the oil out of your right boot ev­ery 100 miles or so. As a re­sult, my en­gine is al­most oil-tight with only a few spots of oil from the cam­box af­ter a good 60 mile thrash at high­way speed.

‘We used Three Bond sealant (the white one) wher­ever pos­si­ble. The bevel hous­ings have never leaked a drop. We made the cam­box as oil-tight as pos­si­ble by mak­ing sure that the cir­cu­lar al­loy muff sur­round­ing the cams is un­dam­aged. Mine was bro­ken, so had to be re-welded.

‘I also took great care in en­sur­ing the sec­tions of the rock­ers which act on the felt wipers were per­fect and pol­ished to a good fin­ish. We also dis­carded the felt wipers. I fash­ioned some ap­pro­pri­ately-sized neo­prene cork sheet (left over from the dis­carded part of a car tap­pet cover gas­ket), which was wrapped on both sides by a red sil­i­cone sheet ma­te­rial of about 1.5mm thick. This ma­te­rial is ex­tremely ex­pen­sive and used in the min­ing in­dus­try. As we had lots of mines around our area, I was able to get a small of­f­cut which would be big enough to do all the In­ters left in the world!

‘ The sheet was bent in a U shape around the neo­prene cork so it ended up with the two loose ends press­ing on the rock­ers. I shaved both ends into a sharp blade in the same man­ner as a wind­screen wiper and then put it all to­gether. These wipers were used top and bot­tom and have worked spec­tac­u­larly well for al­most 20 years at keep­ing the vast ma­jor­ity of the oil in. I use min­eral oil in the mo­tor, nor­mally straight 50, and use the high­est oc­tane fuel I can get, and al­ways en­sure it is fresh.’

In keep­ing with the in­tended pur­pose of the In­ter­na­tional, Rowan went for a high­per­for­mance spec; Manx cams, high-comp pis­ton, TT carb, close-ra­tio gear­box and a tacho. But there are down­sides to fast liv­ing. ‘When I first re­stored the In­ter, I didn’t have the nut on the end of the camshaft tight enough, and it came loose, al­low­ing the cams to move, and I bent an ex­haust valve.’

Then in 2002, ‘the pis­ton melted due to poor qual­ity fuel. The bike was pink­ing badly, and lost con­sid­er­able power. While try­ing to get home, I played con­tin­u­ally with the ad­vance/re­tard and fu­elling as much as I could, but 60km from home the mo­tor par­tially seized. It also broke a cou­ple of teeth off the bot­tom bevels, which was quite a dis­as­ter. I sourced some bevels and a new pis­ton, and got it back on the road in a few months.

‘Af­ter I trashed that pis­ton, I went for a lower com­pres­sion pis­ton made lo­cally here in Aus­tralia. Whilst ul­ti­mately the per­for­mance is not quite as good as be­fore, it is much eas­ier to live with. It has not let me down since.’ So what’s it like, liv­ing with a leg­end? ‘Start­ing is easy hot or cold,’ says Rowan. ‘I had the mag­neto re­fur­bished at restora­tion, which helps sig­nif­i­cantly. Cold start­ing pro­ce­dure is to tickle the TT carb un­til it floods, and close the air slide. Af­ter that re­tard the ig­ni­tion about a quar­ter from full ad­vance and give the bike a smooth but hefty kick. It will start on the first or sec­ond kick usu­ally, even if it has not been used for some time. Fresh fuel is im­por­tant. If you give it too much ad­vance, it will give you a fear­some kick­back, but just re­tard it a lit­tle from that point and away it will go… ig­nor­ing the pain in your foot and an­kle of course!

‘ The close ra­tio box is not much fun around town or two-up. First gear is quite high, and there is a gap to sec­ond (It has the fa­bled 20/22 tooth com­bi­na­tion sec­ond gear fit­ted) with the top three ra­tios quite close to­gether. It is magnificent go­ing up and down through the gears on a good windy road though. I hate rid­ing two-up es­pe­cially around town as the com­bi­na­tion of the ra­tios, the TT carb and Manx cams makes it an in­ter­est­ing pro­gres­sion be­tween traf­fic lights.

‘ The clutch seems to put up with the pun­ish­ment of town rid­ing quite well but does start to com­plain, be­ing grabby af­ter a while. Luck­ily, I live out of town so can stretch the bike’s legs al­most im­me­di­ately. It’s an ab­so­lute joy to ride once you at­tain about 40mph.

‘As for the brakes, well, they’re about what you would reckon for a 1949 bike. I did the best I could with them and used quite soft, or­ganic lin­ings which were done for me at a lo­cal brake spe­cial­ist. They wear quickly but have nice feel and are quite pow­er­ful. Pow­er­ful enough to com­press the forks sig­nif­i­cantly when strong brak­ing is nec­es­sary, and the back wheel can be locked with rel­a­tive ease. Hav­ing said that, it is pru­dent to ride with some an­tic­i­pa­tion of what is go­ing on in front of you to make sure you can stop in time.’

So even though the ‘ex­perts’ might not think so much of the plunger In­ter­na­tional, this owner def­i­nitely be­lieves his ef­fort and ex­pense were ‘en­tirely worth it. I have a nice col­lec­tion of bikes and the In­ter is my stand­out favourite both to look at and to ride.

‘It’s quite rightly a clas­sic ride, es­pe­cially if you re­store it your­self. On back roads and when it comes on the cam it makes a great sound, and has the per­for­mance to match.’

The sohc In­ter en­gine was of­fered in 350 and 500 forms. As you’d ex­pect, the 350s lacked the torque of the big­ger en­gine but re­sponded well to a big fat hand­ful of revs. This is a 1949 490cc Model 30 which found its way to Aus­tralia Set­ting up the bevel-driven over­head cam is a la­bo­ri­ous process, but you can achieve an oil-tight en­gine with pa­tience and (in this case) mod­ern ma­te­ri­als. Neo­prene and sil­i­cone can work won­ders!

Above: Nor­ton of­fered an op­tional bronze al­loy head from 1935, but the valve seats tended to sink so it was typ­i­cally only used on track, and road rid­ers stuck with the cast iron head A pukka TT carb, cor­rectly ac­ces­sorised. Owner Rowan says ‘If I in­ad­ver­tently leave the bath plug in the bell­mouth and try start­ing it, then I can for­get kick­ing it over for a few min­utes. It nor­mally starts very well af­ter that’ It’s all a bit of a tight squeeze, fit­ting in the TT carb along­side the su­perbly-styled six-pint oil tank with its ex­tended filler neck es­pe­cially de­signed to suit the TT pits Purists tend to pre­fer their cammy Nor­tons with the fa­mous feath­erbed frame, or to have a rigid rear end. But back in 1949, the plunger chas­sis was praised for its com­fort over cob­bles and the like Although Mo­tor Cy­cling would’ve liked the front brake to have more bite, they were im­pressed that it stopped 390lb of mo­tor­cy­cle from 30mph in 31ft… in the wet. In the dry, it could eas­ily squeal the front wheel A glimpse be­neath the fuel tank re­veals the ex­posed hair­pin valve springs

By the 1980s, this gen­er­a­tion of In­ter­na­tional had fallen out of favour. But when it was new The Mo­tor Cy­cle said that ‘few rid­ers could ask for more. It will cruise ef­fort­lessly and in­def­i­nitely in the seven­ties and do so with a de­gree of rid­ing com­fort that has to be ex­pe­ri­enced to be ap­pre­ci­ated…’ This was what hap­pened with low-oc­tane petrol and a high-comp pis­ton on a high speed, long dis­tance ride. ‘I have learned to read and lis­ten to the signs much bet­ter these days,’ says owner Rowan. Since then he’s cov­ered 6000 trou­ble-free miles

By mod­ern stan­dards, this is a com­pact mo­tor­cy­cle. But com­pared to the rigid In­ter which pre­ceded it, the plunger-sus­pen­sion bike was heavy and quite tall

Rowan’s wife is ‘pos­si­bly the best pas­sen­ger in the world,’ he says. ‘How­ever she de­spises the pil­lion po­si­tion on the In­ter and doesn’t like her perch be­hind me. She has re­fused to ride on the In­ter since we got an early BMW. This suits me fine as it is much eas­ier to live with as a solo mo­tor­cy­cle’ Left: Yes, that’s the op­tionalex­tra tacho to match the Manx cam and TT carb. Given Rowan’s ex­pe­ri­ence with a melted pis­ton, it’s wise to keep an eye on the revs… Left: The In­ter en­gine is some­what stran­gled by civil­ian si­lenc­ing. Owner Rowan says that when he tried a straight-through ex­haust ‘the In­ter is a very dif­fer­ent (nicer) beast when it can breathe prop­erly and stretch its legs. Un­for­tu­nately it also rat­tled quite a few win­dows in the process!’

The In­ter is all about rid­ing, #1. Rowan Bond gets to grips with his

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