Cycle News - Archive Issues - 1990's

~ ROA DRACE Four-strokes in GP racin ! What once was, and might have been Q") ......... By Michael Scott Photos By Alan Cathcart o ur-stro kes in Grand Prix road racing! It is not an idea to be taken lightly. The proposal to let them in for 1991 evoked the strongest of reactions. T o the ma nagers of race promotion on TV, the fo ur-strokes meant salvatio n - a way of bringing up the n um be rs o n the g ri d to th o se deman ded by TV network s. To the established 500cc class riders, the four-strokes co nj ured up visio ns of secon d-ra te rider s o n cl apped -ou t superbi kes, to uring ro und and getti ng in the way, and from tim e to time blowing up and spilli ng oil on the racing line. Rank opti mists envisaged the earl y return of hi gh -tech mul ti-rev screamers, starting wit h the ova l-piston Honda NR 750. And mor e than one generation of rheumy-eyed fans enjoyed a reviva l of dear memories that range from throb bing No rtons a nd sp luttering V-8 Moto-Cuzzis through to howling red Gi leras, MV Agustas and shri ll multicylinder Hondas. In the end, the FIM overt urne d th e suggestio n to open the 500cc class to TT-FI machines, preferring torevi se the technical rules to broaden th e cu rrent overacute pyramid of technol ogy . And never forget th at four-strokes have man y cham p io ns in racing 's F did mu ch of th e glamour of raci ng die with the last ho peless ho wls of the 500/ 4 MV Agu sta in 1974 - the last fourstroke motorcycle to win a World Championship. The NR500 also mad e the established opposi tion look very fast. The dim inutive screamer mad e a symbolic raci ng debut at the British GP, where Mick Grant's mach ine leaked oi l o nto its rear tire a nd crashed in flames at the very first corner. It was lying last, at the time. Honda str uggled o n wit h the NR, eventua lly aba ndo n ing the rad ical fram e for a British -design ed tubular struc ture. But never go t close enough to the two-strokes to pose any thi ng of a threat, Meanwhil e, th e m achin e gave ammun itio n to such two-stroke fan s as Kenny Roberts, for it was living and a lmost priceless proof that wha tever else they ma y be, four-strokes are extrao rdinarily complex and expe nsive to bui ld, let alone to maintain or repair. This was not always so. It was escalating power o utp uts, driv en by th e intensity of the war between th e J ap an ese factories, whi ch contained with in itself the decisive two-stroke/ four-strok e battles, th at caused the escalation of expe nse - the leadingedge machines were always com plex, bu t in their heyday" sing le-cylinder four-strokes of all capa cities were the privat eers' sta lwart. Indeed, in th e More Italian: A 1957 500cc four-cylinder Gilera, 22 es ta b lis h m en t, ra nging from th e H onda factory to sever al di ehard man agement men . The idea maynot go awa y, Two-stroke engines have given a great dea l to raci ng . In the course of achieving domin at ion, begun in the '60s, confirmed in the '70s, the y have un leas hed un precedented po wer out p uts from engi nes of extrao rdina ri ly ligh t weigh t and mechanical sim plicity. And they have given. birth to a generatio n o f in spirational engineers whose sym pathy with and understandin g of intern al combus tion engines as resonating - indeed musical - devices has led to an individual hall of fam e reaching from MZ's Walter Kaaden to modern luminari es like Erv Kanemoto. But two-strokes have never won th e hearts and minds of the people to th e exten t of th eir mech anicall y more comp le x (tho ug h a sp ira tiona lly simp ler) predecessors. J ust as to the vast majorit y a Du cat i o r other twin sounds like "a real mo torcycl e," so also confectio ns can only be given a backward glance. The new World Champi onship was instituted under a postwar ban on supercha rgi ng, which changed the technical profile of racing. Amo ng the bikes tha t do n 't fall wi thi n our am bit are the Velocette " Ro arer" a wonderfu l twi n-crank two-cy li nder blower whose exp loits were terminated prematurely by war; and th e blown flat twin raci ng DM Ws. Anoth er sa d casua lty is AJS 's over head cam superch a rged V-4, a no the r short- lived extravagance. It was an AJS th at opene d th e scor ing after the war , winnin g the first World Champion ship in the hands of Art ie Bell. T he machine was a twincam parallel twin with spi ky finning a to p th e fo rw ard -canted cyl i nder head s, hence the deathless ni ckn am e " Porcupine." T his was a tim e of post-wa r aus teri ty and very variab le-q ua lity fuel. This last facto r favored simpler mach ines, if for no ot her reaso n than that fewer cylinders co uld easily be spa ced to vary th e co m p ressio n ratio to suit th e ga soline of the da y. Even so, pow er was - well, powerfu l, and th e way to get it was by in creasing revs, a goa l ac h ieved ins tant ly by adding more cyli nders wit h sma ller and lighter reciprocating pans. The Gil era, whi ch triumph ed in 1950, used a definitive four -cylinder twin- overhead -cam shaft engine littl e A classic: The Mota Guzzi V-eight 500cc GP racer. sma ller classes, th ey were also the ba ckbone of th e factor y efforts. A typical No rton. Mat chl ess o r AJS could ru n just about a wh ole season with little more than sprocket cha nges', refaced clutch plates, fresh chains, and the valves lapped in from time to time . But these workaday bangers are not the stuff of legend, and it is surely the legends that deserve to be rememb ered. Machines lik e the Gil eras and MV Agus tas, and Moto-Guzzi's aston ishing variety of racers rang ing from singles to wid e-angl e Vvtwins and ultimat ely to the legendary V-8 - the Ital ian s espo used expone nt ial compl exity when Mr. H onda was still bolting putt-putt en gin es o n to bicycles. The GP four-strok es represent a fascin at in g array of ma chines, but becau se it is necessary to pick a starting po int, and true World Ch ampion ship GP racin g on ly began in 1949, we mu st relu ctantly discard a few wonderfu l crea tions from this improm p tu survey. T hus th e pre- WWII supercharged d ifferent in o vera ll design from a m od ern un it , but for it s stric tl y hemi spherical combustion cha m ber. With its cylinders and handsome cam covers cant ed forwards, it was a direct development of the earlier Rondi ne, a pre-war supercharged 500 four . and its wai li ng note sent shivers dow n the spine. Its biggest drawback, agai ns t the arc hety pa l Norton sing le, was its wid th and weig h t, whic h imposed great demands o n the pri miti ve fram e techno logy of th e tim e, and ga ve rise to a number of experiments with rear suspens io n, Italian design ers favored parall elograms and o ther elaboratio ns, a lt h o ug h Moto-Guzzi devel oped a prescient underslung monosho ck system th at has echoes in today 's risingrate systems. Norton, meanwhile, stuck with their faithful single, and exp loi ted its slim bu ild and relatively light weight wi th one of the most im portant adva nces in frame design of a ll time - the legendary Fea th erbed of 1950, T his twin-crad le affair wit h i ts sim p le p ivoted trailing rear fork (ever since mi snamed swing-arm, forcing modern true swing-a rm systems to be dubbed "si ngle-sided") set a fashion for frame design that was o n ly superseded in the la st decad e. with fabri cated spine fram es suc h as Yamaha's Deltabox. T h us while Maseui' s Gilera took the 1950 a n d 1952 titl es, ro ad -racing gen ius Geo ff Duke man aged one more 500cc title (1951) and two more in the 350cc class for Norton, with a triumph of ridi ng ability and machine agi lity over brute force. By now , as well as the Gi leras and AJS and Guzzi twins. Norton 's trusty pre-war design was facing a n ew co m peti to r - -MV Agusta , playt hing of bi ke manufacturer and wealthy industrialist Count Agu sta, and to becom e one of the gr eatest nam es in racing. We wi ll hear th e name again. Nobod y could say th at the current generatio n of sym biotic sports bikes / race bik es are going to rep lace that glamour. The fact that yo u can take the head light off a street bike and expect to be halfway co m peti tive makes brilliant street bikes, but unexciting racers. Rather, we need loosely fram ed ru les that .will revive exo tic prototypes, of course. like the Norton Ro tary which, altho ug h no t exactly a four-stroke. isn 't a two-stro ke either. But the rea l bike o ne wo uld like to see is the Honda NR750, the o valpiston 32-valve charger that, by no coinci dence, is a direct descendent of th e last four-stro ke in 500cc class GP racing. Honda 's NR500 had an inglorious ca ree r, full y earn in g the sco rn fu l nicknam e " Never Ready" - but it was a glo rio us ma chine all the sam e, as anyone knows who saw and heard Freddie Sp en cer running it up to 22 .000 rpm s a n d fift h ov erall at Silverstone for its final G P ou ting in 1981 or in its one appearance in Ameri ca at Lagu na Seca the same year wh ere it sa t on the po le for the National. He did not finis h the Silverstone race, nor did he fin ish at Laguna Seca, and subseq uen t accusatio ns that the mach ine was oversize. a nd tha t he retir ed delibera tely at Silverstone, serve o nly to add further clo ud.s' of mystery to a very conte ntio us exerc ise. Honda admi tted in the end that they had been hoist by the rule book. Had th ey been all owed to fi t their defiant four-stroke with more than the permitted fou r cylinders, they felt they could have put it on equal terms with the two-stokes. It is debatable, but worth debating; for they came reasonably close with what they were allowed to build, even if they had to push technol ogy to the ou ter limits. at a cost th ey ,have never revealed, but which was sure ly mor e than any othe r manufacturer could contem pla te. T he NR500 was nothing if not exotic. It firs t appeared in 1979, and

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