Cycle News - Archive Issues - 2000's

Benelli 250cc Quattro Racer th e revs m o u nt and it sta rts to m ak e g o o d power f rom arou nd 8000 rpm upw ard . Provi ni, of co ur se, wo ul d h a v e ex p lo ited th e up pe r reac hes of the p ow erb an d all th e t ime, but even wi th due res pect for t he Bea le h an d iw o rk, it' s ea sy to kee p th e engi ne driving h a rd , witho ut ex p lo ri ng t he 14 ,0 0 0 rp m p ower pe ak of this eng ine in its h e y d a y. Th a t' s b e c au s e t he s ho rt , p recise gearsh ift action gi ves access t o a cleverly devel o ped set of ra tios a n d s in c e t he gea r box ha d to b e m ad e fro m n ew for th is b ik e , th ey 're co pies of t he o nes in M o rbid elli 's own ' 6 5 bike . Botto m g ea r is v er y lo w, for e a se o f sta rti n g - an d I'm no t sur prised th at Pro v ini was regu larl y first away . Th e bi k e also has a li ght -ac t io n cl ut c h lever that all ows you t o g oose it u p into the pow erband rea ll y easily . Th e n t h e n e x t fo ur ge ars are a ll ve ry c lose t og eth e r , b ef ore a quit e n o t i c e a b l e ga p b et w e e n f i f t h a nd sixt h, wh ich h a s t o p (sevent h) gear ve ry cl o se to it. Thoug h Ben e lli was o ne o f t he fi rst to hav e an extractable @[JD@ ®(] @ wil[JD@ Because of th eir limited resources, Benelli didn't build mor e than a dozen examp les in all of Savelli' s sem ina l '60s four-cylinder 250cc ra c e designs d uring its deca de of development leading ultimate ly to the acco lade of Kel Carruthers' world title. The later early- '70s SaarinenjVilia bikes were a compl ete ly different desig n , by hi s successor Piero Prampolini , whereas the Savelli bik es, though each subtly different from the other, as befit s a hand-built family of bike s under constant R&D for more than 10 years - all had t he same very distinctive forma t that was com pletely different from any other inline raci ng four. T his saw t he crankca se and unit-co nstructio n gearbox casi ng of the 44 x 40 .6 mm 247cc engine - all 250cc Benellis had the sam e dimens ions - com pris ing a single large but light alum inum ca sting (m agnesium was also used), with a large rectangular front crankca se cov er and four round side co vers, thro ugh whic h th e engine inte rnals were slotted to build up the engine. If rather more inac cessible than a horizontally split engine, this ma de for a very rigid and lig ht oil-tight design, with two of the side covers locating the ends of the six-bearing, pressedup crankshaft in ball bearings, and a central spur gear off the crank which drove not only the oil pump and a m agn et o m ounted in front of the crankcase, bu t also a train of thr ee gears up the center of the 'engine, driving the double overhead c amshafts. As the mach ine on which Provini won the 1964 Spanish GP, in his first World Cham pionship race as a Benelli rider, our test bik e may be consider ed as the first 'evo luzione' version of the Savelli prototype design raced by Grassetti in 1962/63. This therefore has two -v alves -per-cylinder , a 25m m inle t and 23 .5 mm exhaust, set at a slightly prehisto ric included angle of 90 degrees - iater versions came with a 63 -degree va lve angl e, and there were also 16-v alve engines later on, though Carruthers raced most of his title season on an eight-va lver. Un li ke other Itali an in-line fours, the Benell i has a two-piece cyl inder head wit h two sy mmetrical hal ves , each serving two cylinders, and eac h with a pa ir of bronze sk ulls inco rpor ating the valve gUides and combustion cha m ber fo r it s ap pro p r iate 40 JULY 5 , 2 0 00 ' cue I e Strangely enough, the rev-counter spins counter-clo~kw ise. g ear cl us te r to m ake sure you h ad th e right ge a r fo r each part of every ci r cu it, Prov in i's own bi k e h as th e sa me a pproxi mate ra tios as m i n e , a n d w h en I rode it, h e to ld m e w hy. "So m et im es on ve ry fast circu it s, we used t o ru n with very tall gea ri ng l i k e a t Monz a , f o r in st anc e . " h e ex p lai ned . " H aving th e top t wo g ears clo se t og eth e r was li k e h av ing an ove rd r ive, w hich cou ld b e inval u ab le of y o u ca me o n a slowe r r ide r _in a fast tu rn , for exam p le . T h en the m id d le fo u r g e ars a re close t o g et h e r to kee p th e e ng i ne pu ll ing h ard on a t ig h t c irc u it li k e M ontju ich - I wou ld o nl y g et top g ea r t h e r e o nce eac h la p , but I h a d a g ea r for every co rner." St ill , wi t h its cl ea n pi c kup an d re latively go o d torque fo r a four- c yl inder multi , th e B en ell i is much m ore fo r g iving and easier to r ide th an a p ea ki er Ho nd a 250cc fo ur, and espec ia lly th e six - let alo ne any m id-'60s two- st ro ke f rom MZ, Suzuk i o r Yam a h a , m a int en anc e a n d p arts repl ac em ent w it h a ra zor th in po w e r b and an d . n ot always being k e pt up t o scratch ap pe t ite for se izu re . M echan ic ally , t he Be nelli w as also b ec au se o f b udg et and pa rts ava il T he B en elli h as fing ertip ha ndli ng , b i g g e st bu gbea r in t he early d a y s , id ea l for slo wer ci r cuit s, w h ic h h o w - until the arri v al of th e Merc ury m ag - e ve r, n et o fixe d th at. A ft e r wa rds , it was 1250m m w heelbase, is n 't as nerv o us rea lly j ust a quest ion of prev en t at ive as t he 250 Paton t w in I used to race coils, with the points driven off the end of the cy linder. Pistons are forged three-ring com inlet camshaft . But these were prone to float ponents wit h deep valve inserts delivering ing at high revs , and so w er e i nitially 10.8:I comp ression, running in four indiv idu replace d by a Lucas m agneto used on Gilera ally cast vertical five-stud finned cylinders and MV 500cc fours, drive n off the central with cast iron liners - though an early form of tim i ng p i nion, But t he sma ller Ben ell i chrome bores was also experimented with. engine's higher revs were beyond the scope Beneili was a leading edge advocate of of the Lucas m ag, so in late 1964 this was alternative technology, not afraid to experi replaced with one from a two-strok e Mercury ment where others were reluctant to do so four-cyli nder outboard engine, whic h cornhence not only the experiments wit h chrom e pletely resolved the problem. bores but also tit anium connect ing rods, plus Having begun, according to Savelli 's own the fact th at all Benell i four-cyli nde r race adm issio n, by developi ng only 36 .5 hp at engines featur ed an extractable gearbox to 12 ,5 00 rp m fo r its Im o la debut in 1962 enable internal ratios to be changed quickl y (against 33 hp at 12,000 rpm for the ultias is com monplace today. A lso , Benelli was m ate 'evoluzione' version of the Ambro sini the first factory GP team in any country to fit singl e). by 1964 the 250 Qua tt ro was prodisc brak es to their motorcycles , as in 1965 ducing 45 hp at 14,000 rpm at the gearbox, when Provini - a big fan of discs, because of rising first to 48 hp at 14.500 rpm for 1965, the im proved steering and bett er suspension then to around 50 hp at 15,000 revs for '66 com pliance - raced mu ch of the season wit h onwards, still in eight· valve form: the later a pair of small seve n-i nch U.S.-m ade Air 16-valve eng ine ga ve a rep ut ed 55 hp at heart discs used in kart raci ng on the bik e, 16,000 rpm , but was m ore peaky to ride addi ng a third at the rear before eventually hence the reason Benelli also experimented removi ng th em o wing to restric t ed pa d with a m ore torqu ey 12 -val ve mo to r, with choice-a nd poor wet weather brak ing. An d wit h former Mondia l and Ducati race engi - twin inlet valv es and a single exha ust. By then, a bank of 24mm Dell'Orto carbs would neer Renato Arm aroli (who later com m ishave been fitted , with specia lly tun ed inlet sioned Savelli to design another four -cy linder stubs responsible for a 2 hp top- end power 25 0cc rac er , th e MT 25 0 d ev elop ed in incr e a se on th eir own, o r m or e torqu ey Barcelona by Du cati ' s Mototran s Span ish 22 mm ones for tig hter ci rcuit s - but t he subsid iary ) orig ina ll y in charge of R&D, it 20m m ones fitted to the test bik e came from was perhaps inevitable that a desmodrom ic the orig ina l Grass ett i '62 prot ot yp e. It sti ll four-cylinder Benelli 250 was projected, only runs ok ay with them, though . to be disca rded when the cornplica tion and Th e original rather crude-looking chassis additional reciprocating weight weren't born of the Grassett i prototyp e was replaced for out by increased power. 1964 and the first of the Provini years by a During 1964 , both Savelli and Ar ma roli moved on, the latt er replaced by ex-Mond ial • m ore work manlik e looking small -scale version of a Nort on Featherbed frame , lighter as engineer Om er Merlolli, while Motobi magi'clan Primo Zanzani wa s move d over from well as m uch lower than before, wit h a carefully shaped ' anatomical' fuel tank containBenelli 's sister brand to ta ke ca re of the ing 7.5 liters in short cir com pany's four-cylinder GP race effort It was cuit form, as on the test his well -focu sed effo rts t h at refi ned the bike (a nine-liter version Benelli into a genuine contender for victory. was used for longer GP The seven-speed gearbox fitted by 1964 was m o st com mo np lace on t he bikes , races) , sitting barely any hig her t han t he up pe r tho ugh flve-, six - and eight-speed versions frame rails. were also used : all fea tured primary dr ive But the Benelli was taken off a large pinion bet ween the first and st ill a small bike, with second cranks haft journals on the left , run j ust a 1250mm wheel ning through a mu lti-plate dry clutch. The base in spite of the perrelatively long forged rods run in caged roller fectly miniaturized fourbearings, with plain bearing lillie ends, and cylinder engine , an d full -circle pressed-on flywheels. we ighed on ly 244 Orig inally, the oil tank for the dry sump pounds dry, split 50 /50 engine was located under the seat , but by between fron t and rear. '62 this was replaced by a typ icall y Italian long, finned sump con taining just two liters Dating from the pre-disc brake days, the '64 bik e of Castrol R and bolted to the underside of has a pai r o f Old a ni the engi ne, Sim ilarly, ignition on the Grassetdru m bra k es, th e front ti prototype had been by batt ery and four n e _ s ab ili ty. pret t y r el ia bl e , w i t h i g ni ti o n i t s i n sp i t e of th e ve ry sho rt 23 0m m fou r leading -shoe version mounted on 3 5 mm Ce ria ni fo rk s wh ic h were t he benchma rk front suspension of their day. Painted in the distinctive if drab slate gray that was the tra dema rk color of the Provini era, before the com pany 's green and silver house colors 'were reinstated for the Pasolini days, this exquisite litt le motorcycle was the passport to the long awaite d world title which the persistence and dedica t ion of the little Italian factory eventually achiev ed as its just r eward . B ut a lthoug h , t ha n ks t o force m ajeur e, he wa sn't the one to brin g them that title, Provini recalls his days racing for Benelli with pleasur e, ti nged with a little regret. "It was a ve.ry happy team ," he says, "and because it was so small , yet was part of an establis hed m-anufacturer, we were able to get things done very quickl y. By the tim e l'd fini shed with the fram e the bik e handled really rather well - I think the J apanese in partieular were surprised just how well, especiall y Honda at Montju ich in '64! Th ey were always photographing it, so they mu st have thought we kn ew something they didn' t! But power was always m y probl em : the Honda four s were j ust that bit quicker, and the Yama ha twins abo ut 10 k ph (6 mph] faster , wh ich was qui t e a lot. Stra ngely , even though it was less powerful , the Morini single was in many ways a mo re com petitive bik e at the time, because it had a lot of power low down for a 250, and consequently you could ride it h ard er eve ry whe re bec a use of it s good to rque. But the Benelli was event ually the best It ali an qua rte r -li t er fou r- str oke eve r made, and I'm only sorry that the way things work ed out, I wasn' t able to win the World Champ ions hi p on it t hat th ey eventua ll y achieved, thanks to Carruthers."

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