AMC twins

From start to fin­ish

Old Bike Australasia - - CONTENTS -

The eco­nomic de­pres­sion saw AJS in liq­ui­da­tion in 1931. The mo­tor­cy­cle com­po­nent of the busi­ness was bought by the Col­lier Broth­ers, trad­ing as Match­less Motor Cy­cles Lim­ited. The AJS fac­tory in Wolver­hamp­ton was closed and both brands were produced in the Plum­stead Match­less fac­tory in London. The com­pany name changed to As­so­ci­ated Motor Cy­cles Lim­ited (AMC) af­ter the pur­chase of Sun­beam in 1937. AMC’s main pro­duc­tion of mo­tor­cy­cles up to 1949 was based on sin­gle cylin­der ma­chines, but mar­ket ac­cep­tance of par­al­lel twins forced AMC to fol­low suit.

Why so spe­cial?

Par­al­lel twin en­gines have two pis­tons side by side. If they move ver­ti­cally they are also called ver­ti­cal twins. Com­pared to an equiv­a­lent sized sin­gle cylin­der en­gine, the big thump power stroke is di­vided into two smaller thumps mak­ing power trans­fer more pro­gres­sive, less ag­gres­sive and with less vi­bra­tion. Di­vid­ing the com­pres­sion stroke in half means eas­ier kick start­ing and de­com­pres­sion mech­a­nisms are elim­i­nated. Par­al­lel twins re­quire smaller fly­wheels, sav­ing weight and pro­vid­ing quicker, smoother ac­cel­er­a­tion. Com­pared to a V-twin en­gine, the con­fig­u­ra­tion is more com­pact, usu­ally lighter, al­lows a shorter wheel­base and lo­cates more weight (ideally) nearer the front wheel. The ex­hausts are side by side ex­it­ing each side in equal lengths for ideal back pres­sure equal­i­sa­tion. The plumb­ing for the in­let is easy and one car­bu­ret­tor can be shared. The cylin­ders and the ex­hausts are di­rectly in the air stream for more ef­fi­cient and even cool­ing. The com­pro­mises are that par­al­lel twins don’t pro­duce as much torque as sin­gles and are not as smooth run­ning as V-twins.

Par­al­lel twins go back to 1913 but only be­came com­mon in 1937 when Ed­ward Turner de­signed the Tri­umph ‘Speed Twin’. Turner’s de­sign ad­van­tage was low cost. The Speed Twin’s suc­cess meant Tri­umph’s en­tire range of post-war mo­tor­cy­cles was par­al­lel twins. BSA de­vel­oped a par­al­lel twin pre­war but it didn’t make it to pro­duc­tion un­til 1946. Ariel re­leased their ver­sion in early 1948 with Nor­ton and Royal En­field fol­low­ing later that year.

The AJS/Match­less twin con­cep­tion

Phil Walker con­ceived the AMC par­al­lel twin. Orig­i­nally the chief de­signer at AJS, he mi­grated across when the Col­lier Broth­ers took over. The re­sul­tant OHV en­gine had a bore of 66mm and stroke of 72.8mm (498cc). The en­gine con­sisted of an al­most spher­i­cal, ver­ti­cally split, pol­ished al­loy, dry sump crank­case. Within was a one-piece (Mee­han­ite) crank­shaft with roller bear­ings each end. Unique to AMC was an ad­di­tional sup­port be­tween the con­rods to pre­vent crank­shaft flex. A two-piece shell bear­ing was fit­ted to a large cir­cu­lar alu­minium plate and bolted around the cen­tre jour­nal of the crank­shaft. This plate was re­cessed halfway into each crank­case half and bolted to studs on the drive-side half. The bear­ing shells had in­te­gral thrust wash­ers on both sides which an­chored the crank­shaft ax­i­ally, al­low­ing the roller bear­ings to float lat­er­ally dur­ing ex­pan­sion and con­trac­tion. Re­ports sug­gest this feature came from the pre­vi­ous Match­less Sil­ver Hawk or the AJS Por­cu­pine projects, but whether there was any sig­nif­i­cant ben­e­fit is con­tentious. Struc­turally it re­duced crank­shaft flex but some say it ac­tu­ally in­creased vi­bra­tion at cer­tain rpm. The def­i­nite ad­van­tage was that this al­lowed Phil to chan­nel the main oil feed to the crank­shaft cen­tre where it then dis­trib­uted equally to both ends. Their com­peti­tors had to feed oil from one end, risk­ing oil star­va­tion on the other and re­duc­ing en­gine life.

The con­rods were sim­i­lar-to the AJS Por­cu­pine, highly pol­ished and made from light weight Hidu­minium RR56, the lit­tle end con­nect­ing di­rectly to the gud­geon pin, with split ‘Van­dervell’ shell type big end bear­ings. Studs for the clamp­ing yoke were threaded into cylin­dri­cal steel bars press-fit in holes pass­ing through the con­rod for max­i­mum strength. A cast iron cylin­der bar­rel was de­signed to be used for both right and left side, pro­trud­ing deep (2-1/2”) into the crank­case. In­tro­duced by AMC in 1948, wire-wound alu­minium pis­tons were in­cluded. 18swg high ten­sile steel wire was wound five times into ma­chined grooves in the pis­ton skirt just be­low the rings, then ground to an ex­act size. This re­duced ex­pan­sion of the al­loy pis­ton al­low­ing tighter tol­er­ances to the bore, smoother, qui­eter and more ef­fi­cient run­ning, while elim­i­nat­ing pis­ton slap dur­ing cold start-ups. The bar­rels and sep­a­rate cast alu­minium heads were spaced apart to al­low max­i­mum air cool­ing. The head in­cluded an­gled cool­ing fins on top which di­rected air across and be­tween the rocker boxes. Posts were castin ei­ther side of the valve to sup­port the rocker as­sem­bly. An ec­cen­tric axle sup­ported the forged steel rocker arm. It had a screw­driver slot on one end for valve lash ad­just­ment, and a large flat head on the other end al­lowed clamp­ing to the post with a small bolt. This feature came from the 350cc 7R sin­gle race en­gine. The camshafts ran high in the crank­case onto piv­ot­ing fol­low­ers al­low­ing short push rods made from light, high strength du­ra­lu­min with hard­ened steel tips to be en­closed within the cylin­der cast­ing. The in­let and out­let camshaft was po­si­tioned at rear/front of the cylin­ders re­spec­tively.

Straight cut gears ran off the crank­shaft, ro­tat­ing the camshafts, mag­neto, dy­namo and oil pumps. This was AMC’s first en­gine with shell bear­ings where oil pres­sure is crit­i­cal, so gear drive oil pumps were used. Driven by rec­tan­gu­lar spig­ots nested into end slots of each camshaft, the front feed pump had nar­rower gears (less ca­pac­ity) while the rear pump re­turned the oil back to the oil tank. A bleed line from the feed pump en­sured the re­turn pump was al­ways primed. A felt oil fil­ter was in­cor­po­rated in the crank­case along­side the ex­haust camshaft. Apart from the oil lines to the oil tank, lu­bri­ca­tion was chan­nelled within the en­gine mak­ing it oil tight. The large cast alu­minium tim­ing chest cover dif­fered for each mar­que. The Match­less unit bal­looned in one smooth curve with a small flat area at the crank­shaft po­si­tion dis­play­ing a re­cessed ‘Fly­ing M’ painted red. The AJS ver­sion was a closer fit­ting shape. Two bulges cleared the pro­trud­ing oil pumps and be­tween them was re­cessed ‘AJS’ let­ter­ing painted black. A beau­ti­ful small cir­cu­lar chrome badge was staked to the crank­case drive side. The Match­less badge dis­played the ‘Fly­ing M’ sur­rounded by red vit­re­ous enamel while the ‘AJS’ let­ters sur­round was blue.

The twin twins are born

Dis­played at Earl’s Court in Oc­to­ber 1948, it was 1949 be­fore AMC re­leased its par­al­lel twins. The twin twins were chris­tened the ‘AJS Model 20 Springtwin’ and its sib­ling the ‘Match­less G9 Su­per Club­man’. They were rated 29bhp with the Model 20/G9 birth weights 394/400lb re­spec­tively.

The twins dressed dif­fer­ently with the AJS’s in­clud­ing touches of blue and gold while the Match­less used red and sil­ver. The frame and tin­ware were gen­er­ally in­her­ited from their sin­gle cylin­der fam­ily. The in­ner chain case, oil tank, ex­hausts and the fuel tanks looked sim­i­lar with a few slight dif­fer­ences. The in­ner chain case dy­namo hole was re­moved, the fuel tank un­der­side changed to clear the rocker cov­ers, the AJS si­lencers were left and right handed.

Unique parts in­cluded brack­ets to brace the heads to the frame, Match­less (only) mega­phone si­lencers and ‘Dun­lop­illo’ dual seat, and AJS (only) 4-gal­lon fuel tank. The AJS tank in­cluded a unique screw-on ‘U’ shaped de­flec­tor in the rear cut­away (where the seat front fits neatly) which di­rected over­flow­ing fuel away from the rider’s ten­der re­gions. The AMC twins were only avail­able with a swing arm rear (along with Royal En­field) while other man­u­fac­tur­ers con­tin­ued with their (less so­phis­ti­cated) plunger or sprung hub frames. The AMC patented “Can­dle Stick” rear dampers worked ex­tremely well and the ma­chines were highly ac­claimed for their han­dling. Too many evo­lu­tion­ary changes were made to list in one ar­ti­cle. Many of the frame and tin­ware changes were shared with the sin­gle cylin­der mod­els which sold side by side. The twins evo­lu­tion (and sin­gles for that mat­ter) was driven by the US mar­ket which loved Bri­tish mo­tor­cy­cles but de­manded larger ca­pac­ity more pow­er­ful en­gines. AMC per­for­mance mod­els were reg­u­larly in­tro­duced in the US a cou­ple of years be­fore the home mar­ket and in some cases were ac­tu­ally mod­i­fied lo­cally. Aus­tralia was a ben­e­fi­ciary of the US push fall­ing un­der the ‘Ex­port Only’ ban­ner.

Early life in Amer­ica

Frank Cooper (Cooper Mo­tors) was a keen Cal­i­for­nia mo­tor­cy­cle desert racer and be­came a west coast AMC dis­trib­u­tor. In­dian deal­ers ser­viced the rest of the USA due to a deal with J. Brock­house and Com­pany, a UK con­cern which loaned The In­dian Com­pany a sub­stan­tial amount in 1949. The con­di­tions were that John Brock­house (the founder’s son) be ap­pointed to the Board. In­dian man­u­fac­tur­ing con­tin­ued in­de­pen­dently but Brock­house’s new In­dian Sales Cor­po­ra­tion would con­trol the dis­tri­bu­tion of all In­dian mo­tor­cy­cle pro­duc­tion along with AMC and other Bri­tish brands. The twins were pretty much ex­clu­sively ‘Ex­port Only’ for 1949 and 1950. Most went to the USA but some were sent to Aus­tralia and New Zealand. The

Shep­par­ton Ad­ver­tiser re­ported that Gribben’s Mo­tor­cy­cles had a new Match­less twin on dis­play on 22nd Oc­to­ber 1949. The Daily Mer­cury (Mackay, Qld) ad­ver­tised Match­less twins for sale on the 3rd Novem­ber 1949. Harry Louis, ed­i­tor of Clas­sic Bike is said to be one of a few who se­cured a Match­less twin in the UK. It was 1951 be­fore the home mar­ket got a lim­ited al­lo­ca­tion of twins. The sig­nif­i­cant change was the fa­mous ‘Jam­pot’ large ca­pac­ity rear dampers re­plac­ing the ‘Can­dle Sticks’. AMC’s race depart­ment also put to­gether a com­pe­ti­tion ver­sion of the twin en­gine in the 7R frame. This would be­come the Match­less G45 and its his­tory doc­u­mented in OBA 57. Cooper con­tin­ued pro­mot­ing AMC through rac­ing. A Jan­uary 1952 re­port de­scribed his Match­less G9 prepa­ra­tion for Bud Ekins to tackle the fa­mous Big Bear Run.

USA growth spurt

In 1953 an op­tional rac­ing kit was of­fered glob­ally fol­low­ing re­cent suc­cess at the Manx Grand Prix. It in­cluded higher lift camshafts, twin car­bu­ret­tors, high com­pres­sion pis­tons, rear sets, mega­phone si­lencers and op­tional rev counter. This up­grade was not enough and Frank Cooper needed a larger ca­pac­ity mo­tor­cy­cle to match his com­peti­tors. Re­ports say Cooper built a pro­to­type bor­ing the cylin­ders to suit 750 V-twin (2.745”/ 69.7mm di­am­e­ter) Har­ley Davidson pis­tons to pro­duce 555cc. He cham­fered the holes in the cen­tre web bear­ings to im­prove lu­bri­ca­tion, took it to AMC in the UK and pleaded for them to make the up­grade. He didn’t suc­ceed and re­port­edly Frank

had Dick Brown un­crate new G9s and mod­i­fied the en­gines lo­cally. These be­came known as ‘Cooper Twins’. These early cylin­ders had ex­ter­nal grooves (just be­low the base flange) al­low­ing oil pas­sage to the top end. When Cooper bored these cylin­ders, very thin walls re­sulted at the grooves. The In­dian Mo­tor­cy­cle Man­u­fac­tur­ing Com­pany closed in 1953. Brock­house quickly or­gan­ised In­dian re­place­ments by paint­ing Royal En­fields red, re­badg­ing them and con­tin­ued busi­ness while con­tro­ver­sially sell­ing AMC ma­chines in the same show­rooms. In 1954 AMC in­tro­duced a 69.0mm bore, 544.4cc model. A re­port stated a for­mer AMC em­ployee Brian Slark (a now Mis­souri dealer) pres­sured AMC for an up­grade. This re­port didn’t men­tion Cooper, but it may have been both that fi­nally got AMC to act. The weight re­mained the same but power in­creased to 32bhp. ‘Ex­port Only’ and cre­ated hastily, AMC shipped these ma­chines with an ex­tra (loose) parts list and chris­tened them Match­less G9B and AJS Model 20B. AMC re­moved the grooves from the base of their cylin­ders and in­stead cut a pocket into the left hand crank­case. The re­sult re­moved the thin ar­eas of the Cooper twins and made them easy to tell apart. A 1960 AMC Ser­vice Bul­letin listed 247/165 Match­less G9B and 204/136 AJS Model 20Bs were ex­ported in 1954/1955 re­spec­tively. In 1955 the race kit for the G9 now in­cluded the rev counter, rac­ing mag­neto and rac­ing sprocket as­sem­bly with a large ca­pac­ity oil tank of­fered as an op­tion. Frank Cooper ad­ver­tised two vari­ants of the 550cc twins. Stan­dard was the ‘Su­per Club­man Ver­ti­cal Twin’. The other a ‘Sport Twin’ (both AJS and Match­less) in­cluded al­loy fend­ers, high han­dle­bars, Dun­lop Uni­ver­sal Tri­als tyres and a 21” front wheel which was a twin ver­sion of AMC’s com­pe­ti­tion sin­gle. Was this an­other AMC ‘Ex­port Only’ or did Cooper raid the sin­gles parts bin and mod­ify them lo­cally given that AMC didn’t re­lease a com­pe­ti­tion twin glob­ally un­til 1958?

Grow­ing even big­ger

In 1956 AMC in­tro­duced a 72mm bore, 593cc up­grade. Chris­tened the AJS Model 30/Match­less G11, these burly twins were in­tro­duced glob­ally and re­placed the ‘Ex­port Only’ 550cc mod­els. The new bar­rels were taller in­clud­ing an ex­tra cool­ing fin (now 7) mak­ing them easy to recog­nise. New pis­tons, big­ger valves and re­designed com­bus­tion cham­ber re­sulted in a com­pres­sion ra­tio of 7.5:1 (Model 30/G11) while the Model 20/G9 went from 7.0 to 7.8:1. The listed weight re­mained the same while power was now 33bhp. This year saw Cooper Mo­tors be­come the ex­clu­sive AMC dis­trib­u­tor for the whole of the USA, sev­er­ing links with the In­dian Sales Cor­po­ra­tion. Cooper named the 593cc AJS and Match­less stan­dard twin as the ‘600 Su­per Club­man’ and the ‘600 Sport Twin’ for his com­pe­ti­tion ver­sion. Mar­lon Brando was re­ported to have pur­chased a 600cc Match­less twin which was cus­tom-built for him. In 1957 power fig­ures dis­ap­peared from pub­li­ca­tion. Cooper’s 1958 mod­els were re­named the ‘Hur­ri­cane Su­per Club­man’ and the ‘Hur­ri­cane Scram­bles Twin’. The ‘Hur­ri­cane’ en­gine was an up­grade, ex­clu­sive to Cooper and fit­ted to all four of his mod­els. His ad­ver­tise­ment listed them as in­clud­ing “rac­ing cams, new head de­sign, high ve­loc­ity port­ing, 1/8” larger in­let valve, 8.5:1 com­pres­sion, crossed over and tucked in ex­haust and a big car­bu­ret­tor.” The AJS was listed with a 3.00”x 21” front tyre while the Match­less had a 3.5”x 19” item.

De­vel­op­ing fi­nesse and a com­pet­i­tive na­ture

In 1958 AMC listed four vari­ants of the 498cc and 593cc twins glob­ally. The stan­dard mod­els now had a coil/al­ter­na­tor elec­tri­cal sys­tem. The De Luxe mod­els re­tained the mag­neto/dy­namo and in­cluded the quick de­tach­able rear wheel and flashy chrome pan­els on the fuel tank. Fi­nally, AMC fol­lowed Cooper, of­fered ‘Com­pe­ti­tion Scram­bler’ (CS) and ‘Com­pe­ti­tion Sports Road­ster’ (CSR) ver­sions. En­gines for CS and CSR mod­els had high com­pres­sion pis­tons, light­weight Si­amese (two into one) ex­haust with a sin­gle si­lencer (mim­ick­ing Cooper’s Hur­ri­cane en­gine). The CS mod­els used a mod­i­fied (one piece, fully welded) sin­gle cylin­der scram­bler frame, high bars, wider sec­tion knobby tyres, light al­loy com­pe­ti­tion mud­guards, 2-gal­lon com­pe­ti­tion fuel tank, light­weight com­pe­ti­tion dual seat, a quick de­tach­able head­light and a head­stock mounted speedo. The CSR model var­ied by re­tain­ing stan­dard, han­dle bars, fuel tank and road tyres. In­ter­est­ingly the Si­amese ex­haust (in­tro­duced to save weight) produced an ex­tra 2.5bhp and a nice wide power curve.

Sig­nif­i­cantly, AMC waivered their pol­icy (not to sup­ply the me­dia mo­tor­cy­cles) by of­fer­ing a Match­less G11CS twin to The Motor Cy­cle magazine for an at­tempt at cov­er­ing 100 miles in one hour at a UK high speed track. Vic Wil­loughby cov­ered 102.9 miles in the hour com­fort­ably, achiev­ing a 103.9mph max­i­mum. Alan Baker (magazine tech­ni­cal man­ager) then wit­nessed the en­gine tear­down com­ment­ing favourably on the lack of oil leaks and re­port­ing no ap­pre­cia­ble wear apart from a minute amount of pick-up on the off­side pis­ton. The new, pol­ished, cast alu­minium chain case fi­nally cured the leaks from the ear­lier pressed metal unit. Un­for­tu­nately, AMC re­moved the ad­ja­cent gor­geous crank­case badge at the same time. The USA re­ceived an­other ex­clu­sive up­grade to 646cc, chris­tened the Model 31/G12. The crank­case cylin­der spac­ing pre­vented a bore in­crease so AMC in­creased the stroke to 79.3mm us­ing the cur­rent G11 (7 fin) cylin­der and fit­ted new shorter pis­tons to suit. Cooper’s head­line read “It’s the great­est 40-incher” (40 cu­bic inches in US lingo), and called them “Su­per Hur­ri­cane Twins”. His CS ver­sion in­ter­est­ingly car­ried the older kid­ney shaped

tool­box and open bat­tery car­rier. No AMC records ex­ist and it was re­ported that AMC’s com­pe­ti­tion shop sup­plied them.

Grow­ing pains and a di­vorce

In 1959 AMC in­tro­duced the 646cc twin mod­els glob­ally. It in­cluded a taller 8 cool­ing fin cylin­der, 1/2” longer pushrods, while re­tain­ing the 593cc pis­tons. This was dif­fer­ent to the en­gine sup­plied to the USA in 1958 and it re­placed the 593cc Model 30/G11. The 1958 vari­ants were avail­able but only the stan­dard ver­sion of 498cc mod­els re­mained by year’s end. In­creased vi­bra­tions from the stroked 646cc en­gine was re­ported to cause fuel tank cracks so a new 4-1/4 gal­lon, two half/ver­ti­cally split, fully welded and rub­ber buf­fer mounted fuel tank was in­tro­duced. Crank­shaft break­ages and an ab­nor­mal in­ci­dence of blown light bulbs also oc­curred prompt­ing quick AMC re­ac­tion to pro­tect their stel­lar rep­u­ta­tion. In 1959 AMC de­cided to buy The In­dian Sales Cor­po­ra­tion from Brock­house. This al­lowed AMC to con­trol dis­tri­bu­tion of their prod­uct di­rectly through the ex­ten­sive In­dian show­rooms. Oc­to­ber ad­ver­tise­ments re­ported the merger of the two com­pa­nies and a huge new fa­cil­ity hous­ing In­dian and Match­less spares, ser­vic­ing and show­rooms be­ing built in West Mas­sachusetts. The com­pany was named ‘Match­less In­dian’. Re­badged Royal En­field mod­els un­der­stand­ably were deleted ex­cept for the 700cc In­dian Chief and other sourced mo­tor­cy­cles that AMC couldn’t sub­sti­tute. Frank Cooper lost the AMC dis­trib­u­tor­ship but ad­ver­tise­ments as early as Novem­ber 1959 had Frank now dis­tribut­ing the Royal En­field range.

In­dian blood broth­ers

In 1960 AMC in­tro­duced a nodu­lar iron (aka Noddy) crank­shaft for the 646cc twin. Stamped with the

let­ter “N” for iden­ti­fi­ca­tion, break­age is­sues were cured. New light weight al­loy heads with big­ger ports, re­duced 40 de­gree in­cluded an­gle valves and dual rated valve springs were in­tro­duced. New mod­ern flat top pis­tons in­cluded a high per­for­mance outer perime­ter ‘squish’ area which also re­duced ten­dency for det­o­na­tion with low grade fu­els. The new Match­less In­dian head­quar­ters were opened in 1960 and the US range be­came blood broth­ers, chris­tened with new ‘In­dian-type’ nick­names but re­tain­ing their Match­less and AJS badges. The Model 20/G9 be­came the ‘Tom­a­hawk’, the Model 31/G12 the ‘Trail­blazer’ and the Model 31CS/G12CS and Model 31CSR/G12CSR the ‘Apache’. In 1961 the Model 31CS/G12CS was dropped from the lo­cal mar­ket. Motor Cy­cle magazine tested a Match­less G12CSR in 1961 re­port­ing a top speed of 108mph. AMC’s in­vest­ment and at­tempt at US mo­tor­cy­cle dis­tri­bu­tion wasn’t work­ing and in 1961 an­nounced that it had lost £350,000.

Fam­ily hard­ships

1962 saw ad­di­tional cost-cut­ting and the orig­i­nal Model 20/G9 was sadly dis­con­tin­ued, leav­ing only the 646cc stan­dard and CSR mod­els. Names were in­tro­duced for the home mar­ket. The Model 31 be­came the ‘Swift’, the Model 31CSR the ‘Hur­ri­cane’, the G12 the ‘Ma­jes­tic’ and the G12CSR the ‘Monarch’.

In April a CSR speed kit op­tion was of­fered lift­ing com­pres­sion to 10.25:1, adding hot­ter cams and twin car­bu­ret­tors. CSRs were also of­fered an op­tional fi­bre­glass bikini fair­ing in blue (AJS) or red (Match­less). A replica of AMC’s rac­ing cowl, it in­cluded a small plas­tic screen, speedome­ter, amp gauge and light switch with a head­light sus­pended in place of the race num­ber pad. A tachome­ter was op­tional. A March ad­ver­tise­ment an­nounced a (US only) 750cc model, chris­tened the Match­less G15/45. The ‘45’ be­ing cu­bic inches is hardly an In­dian name but could in­ap­pro­pri­ately be linked to the ‘Colt 45’, “the gun that won the west”. Re­ports state the bar­rels still had eight cool­ing fins, the bore was in­creased to 77mm, com­pres­sion ra­tio 7.3:1 and ca­pac­ity was 738cc. 72mm bore was pre­vi­ously quoted a max­i­mum. Re­ports quoted that this en­gine had very thin (less than 498cc) head studs which may ex­plain how the bore in­crease was achieved. Only avail­able as a stan­dard road model, it had bat­tery/coil ig­ni­tion, a sin­gle Amal 389 carb, 19” front and 18” rear wheel like the cur­rent CSR mod­els.

At 430lbs re­ports stated the ‘45’ was no faster than the 646cc but cheaper than the G12CSR. In Novem­ber 1962 AMC an­nounced that all In­dian Mo­tor­cy­cle rights were sold to Joseph Ber­liner, al­ready a huge dis­trib­u­tor of im­ported mo­tor­cy­cles in­clud­ing AMC’s other mar­que, Nor­ton. The new com­pany be­came J.B. Match­less Cor­po­ra­tion. In­ter­est­ingly Ber­liner never used the In­dian brand name. In 1963 AMC in­tro­duced a new full length si­lencer pro­duc­ing bet­ter low down and mid-range punch when cou­pled with the op­tional CSR speed kit. 18” wheels were fit­ted to the stan­dard model while the Hur­ri­cane/Monarch (Model 31CSR/ G12CSR) re­tained the 19” items. Ber­liner re­moved the feathers and war-paint nick­names list­ing Match­less (only) as G12CS, G12CSR and the G15/45.

Kicked out by their step brother

Nor­ton pro­duc­tion moved in 1964 to Plum­stead and se­ri­ous ‘Nor­toniza­tion’ of AJS/Match­less mod­els be­gan. Nor­ton Road­holder forks re­placed the AMC Tele­draulic units and all mod­els now had 18” Nor­ton wheels. The stan­dard and CSR, 646cc mod­els con­tin­ued with their head studs in­creased to 3/8” di­am­e­ter. The (US only) 738cc AMC twin was re­placed (ap­par­ently only two batches of 100 were ever made) by the 748cc Nor­ton At­las en­gine with a rel­a­tively low 7.6:1 com­pres­sion ra­tio, twin car­bu­ret­tors and sports camshafts. Claimed power was 49bhp @6500rpm. This re­born Model33/G15 was re­leased in Oc­to­ber. Ber­liner who had dis­trib­uted Nor­tons since 1958, be­came a Nor­ton fan and ap­par­ently in­sti­gated the en­gine change. By 1965 the model line-up was a jum­bled col­lec­tion of AJS, Match­less and Nor­ton en­gines in AMC, Ju­bilee and Feath­erbed frames and the model names were dropped. The 646cc mod­els were joined by the 748cc Nor­ton pow­ered twins in stan­dard and CSR form. The 748cc G15CSR de­sign phi­los­o­phy was re­vised to fol­low café racer trends with lower han­dle­bars, rear set pegs, short­ened al­loy mud­guards, front fork gaiters, ex­posed spring rear shocks and swept back twin ex­hausts. The AJS Model 33CSR was in­tro­duced a lit­tle later. The end for AMC came in 1966 when it sadly slipped into re­ceiver­ship. In Septem­ber, Man­ganese Bronze Hold­ings took over, re­nam­ing the com­pany Nor­ton Match­less Ltd. This later be­came a part of Nor­ton Vil­liers who a few years later would also take over the ail­ing BSA em­pire, in­clud­ing Tri­umph, re­nam­ing it­self Nor­ton-Vil­liers-Tri­umph (NVT). The 646cc mod­els were dropped mid-1966, lay­ing the AMC par­al­lel twins to rest and leav­ing their Nor­ton step broth­ers to con­tinue but it wasn’t long be­fore they too faded into non-ex­is­tence.

My 1955 AJS Model 20

In 1981, I re­ceived an as­sort­ment of parts as a house warm­ing present for a gratis job I did on a friend’s mo­tor­cy­cle. From then on I be­gan sourc­ing parts to suit the 1955 twin en­gine. Ev­ery Satur­day with pay in hand I’d head to var­i­ous mo­tor­cy­cle stores and pur­chase what I could. I bought a bitsa to speed things up. Luck­ily I found the unique 1955 spring frame which I swapped a du­plex frame for from the late Stan Wil­mot. Stan also sup­plied the fuel tank which he said was an op­tional long range item. It had the cor­rect un­der­side for the twin en­gine and a screw-on de­flec­tor (ex­clu­sive to early AJS twins) but with cor­rect screw lo­ca­tions for the 1955 plas­tic badge. The unique 1955 through bolt fixed oil tank and bat­tery car­rier came even­tu­ally. I did the me­chan­ics, pol­ish­ing, panel beat­ing and paint­ing while out-sourc­ing the plat­ing and spe­cial­ist ma­chin­ing. Per­haps the most dif­fi­cult part was the rub­ber air cleaner man­i­fold. It is a weird shape so I had to care­fully pro­file some plas­ticine from which I made an alu­minium man­drel which I had wrapped with rub­ber to make the sleeve. The bike took shape in the lounge room un­til com­ple­tion in 2003. I then got my mo­tor­cy­cle li­cense. In­surance was in­ter­est­ing. I rang Shan­nons who were con­tem­plat­ing mo­tor­cy­cle cover and I was to ring a guy (‘Chook’) in the NSW of­fice for de­tails. I sent some pho­tos, we agreed a value and I be­lieve my AJS was one of the first bikes they ever in­sured. It has been a faith­ful com­pan­ion and we have cov­ered many miles and one crash to­gether. While it is a lit­tle heavy for an old guy it is com­fort­able and the twin ex­hausts have a won­der­ful bark at full song and bur­ble on the down shift. Its most fa­mous mo­ment was win­ning ‘Bike of the Show’ at the Laverda Con­cours in 2012.

ABOVE The orig­i­nal AJS twin with the “Can­dle Stick” rear units. BOT­TOM LEFT A page from the 1953 cat­a­logue show­ing the Model 20, now with “Jam­pot” rear shocks.

LEFT Crank­shaft as­sem­bly with cen­treweb plate fit­ted. RIGHT Sec­tioned draw­ing of the AMC Par­al­lel twin en­gine.

ABOVE Fe­bru­ary 1955 Cooper Mo­tors ad­vert fea­tur­ing Match­less 550 twin.

ABOVE The Match­less/In­dian mar­riage of 1960. RIGHT Match­less G9 Su­per Club­man and Match­less G11 from the 1956 cat­a­logue.

Cast frame lug and tri­an­gu­lar plate head brace in­tro­duced 1953. Oil tank fil­ter and fil­ter cap. AJS crank­case badge is a bit of jew­ellery. Unique through stud cast­ing with Vokes air cleaner and rub­ber man­i­fold. Head­light dash­board with bul­let park lights and domed cov­ers over the stan­chion nuts.

ABOVE The unique ‘spool’ shaped 1954 full width al­loy front hub.

ABOVE In­fa­mous pressed metal chain­case with re­mov­able clutch cover for 1955.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.