Cycle News - Archive Issues - 2000's

r CYCLE NEl,r'S . AUGUST 2, 2006 67 the streetbike's wom gear pump, which proved to be oveMhelmed in racing use says Ander$on, and oiliets direcled al the piston croMrs help to coolths enqins. Finally, the XB"f,Bs Siemsns ongine-manage- ment ECt, is essentially a development ol the Fire- bolt's sreet system, with a slighdy faster processinq time. Buell is able to wa nant H v{ To creats$sXB-BR, Erik Buelland his R&Dteam, headed bylorner iournalist and l\rlTgraduale Steve Andsrson, started off with a corefulreading of the Formula XtBme rule boolr before sining down to create an Ame cao racer comprising a marriago ot tradiional values and avam-garde technology. Starting with th€ XB12R tirebolt streetbike s long-stroke 88.9 x 96.8mm.4s-degree, V-twin, dry" sump pushrod 120:cc motor, which provided the basis for the XB-Rfs homologation, the Buellboys crested a short-stroke version of ths same airloil- cooled engine, m8asuring l{8.6x79.4 mmfora capacity of l33gc c. This gives both moro cubos, up to the permitted limh otlhe air-cooled fX subdi- vision, and a more extreme conliguration aimsd at greater power via higher rsvs. To psrmhthis,$ey concocted o new crankcase design, ,rvhich, like tho Firoboh, still incorporates the swingarm pavot mounts, but has a much widerstud pattem sroundthe cylinder bores, and a higher dec k hsigttt than onthe sEeet motor. Thoss newcastings were the principal bone of contention for c ortain vociferous objec' tors loths AMA3 acceptance of the XB-RB, since FX rules allegedly stipulare "stocl craflkcases." Reponedly, Bu€llwas permitted to resolve lhis bymelting down $e slreetcasesand rscastng new ones with tho sam€ mstal. Yes, realV... well, no, maybe not -The air-cooled subdivision otFormula XtIeme does allowuntimhed engine modification," said Anderson. "Butthe premise of Formula Xtreme is producton-bassd. what we did, essentjally, was to produce an evolution of our production sngins, which is permifted by th€ rules.The only compo- nentw€ have to retain is the stock chassis. as w€ have done." vylhin hsso new crankcases srts a pressed- up roller-bearing crankshaft with torgad'steel fly' Meels employi.gtho benchma* H-D "pork chop'format {which are much lightsrthan lhose in the XBI2R strsot motorl to red uce inertia and enhanc€ acceleration. The cronkpin is incrsas€d to l.50inches in diameter ' slifhr and sturdier than the FrEbolfs 1.25-inch pin. Equallytradfional isthe knife-and-Iork layout of ths slesl connecting rodt which are sunno!fitad byfiree-ring Wseco pistons running io Nilasil linsrs and dslivedng tzsl compression. Addilionally, Buellhas I two- ring dE6ign undor development aimed at reducing Iriction widrout suffeing oil blotv-by. The cylind€rsare also new wi$ slighdydeep- sr 6nning to improve heat disps6al from ths more powerfulengins, and a NACA ductin $e leltlai.- ing panel$at directs cooling akto tha r€ar cylin- der laided bycontouring intls left-side trame spar ha dirscs air on to $e rear cylind€r hEad, iust as on tho sreet Frebolt). The cylindEr heads 8rB alsoa now castino wi$ tlre ttrin-stsmmod but souFpl8te-sized 225- inch (',.15 mmljnlotvalves sd fve degrees more upright fian on th6 XBI2B - to deliver a flatter valvs angle aimed at improving combusiion and broathing. lndesd. by loohng staight dorr,,n firough sither of tlle XB-BBt 62mn Walbro sin- gle-injector $rotds bodies with its butterlly wids open, you can closrly see the head of thg msatY intak€ valve. oual valvo springs ar€ smployed, wi$ lie L&I inch {45,72mm) sxhaust valvss leadingto separate meaty, strinlsss-stsel €xhausts ioining up iust as drey enter Bualllrademark csr-type silencsr benea$ lhs Bngine. tike its XB l2R stroet ancss. tor, ths XB-RR features no-maimenance hydraulic valve lifbrs and twin gear-dtiv€n camshalts per cylinder, operated via a traa0 of gears driven off the right sidg ofths crrnk. These in turn ecoate the lour pushrods llat dirEcdy opersle le valvss, and, thsnks to lhsir metal metrix composite con- stuclion $,ilh aluminum borox fiber, $sy are ulllla stiff and very liglt-thus reducing insttia in $e valve rain and enhancinq accoloration. A pair of rotary oil pumps dtiv8n offthe camshafb replace flat esch cuslomer bile ofhe 56 madgthis year will dsliver at l6ast 150 hp atthe crank at 8m0 rym. and $us 50 percem more powerthanlhs stock tirsbolt, with maximum torque of 100loo! pounds/l3.8 mkg at 65m rpm. Andercon rsvsals thatall race enginestertsd sofar have produced belween 148 and 152 bhp at tfie rear wheelon the Buellfactory race shops oynoi€t.This comes thanks to the fullCNC machining of fie cylinder head porting,which permits Buellto accurately clooetie fruits otthsir in-house R&0. "CNC manuf acture allows very repeatable numberson each ng$rengine," says Anderson. "WB can provide our customers whh exacdythe same perromance that allowod Uoremyl Mcwilliamsto passA€ron Gober(s Erion Honda at 170 mph-pluson lhe banking at Daytona, or pull 6m fours v6ry noliceably out of comers, as allthe Buells did there." This substantial power by air-cooled two-valve standards istrsnsmitted via a five-speed, closs- ratio race geaftox andtripl8x chain primarydrive, matchsdto an oil.bath muhiplate clutch.The cus. tomer bikes come with a race-pattsrn gealshift butno powsrshifbr, on the groundslhatthe ECU already has allthe logic needed to adoptone buih into it leaving th6 customertree to source one himself and odapt itlo the bike. A slipper clutch may be in $e works. "Wg wa nt to run one of dlese in tha future, once we find onethals rsliable,- said Anderson, wio r€counted how the Geman XB-RRteam at Daytona broughtheir owlr from Europe, which, however, melt8d its plates under$e hefty lorque ofthe V-twin.Ihe engine has, however, be€n co[- verted lo chain fnaldrivefmm the beltfuotured on tho tirobohand other guell streetbiles, rvhich entoiled tabricating new snds for tho stock 20lF modol Firsboh s1r/ingarm to provide a means of ch8in adiusmem, "lf ws wsrs runningjusta tactory team, we'd havo kept sle bshs," EtatesAnderson. "lfs a much lighter systsm tl,/|lich rqduces unsprungweight and our cunem Kevlar slxeet belts would oasilY absorb the po$,er of $s XB-R8. But for privateert ifs consid8rabls o)fra hsssle and expense to carry diftsrent-lengrh bslts, and tho various pul- leys and idlsrMssts neededto changetre gea,- ing. Going to chah made it easisr for thsm , lhough it r.tould hav8 b8€n oice to have proved a poim by racing wifi belts." Convsrsely, thqrc s rath€r strangely no mov8 yotto adopt bsh pdmary drivs,to replace E riple-row oil-bat chain arrangsmsnt Ihis highly developed buttradilionally sngi- neered motor is installed in Buelfschassis pack- age, which is stilliust as innovative today 8s wfien it was imroduced back in Z 12, compriEinq a stock XBI2R Firsboltfu el-in-f rane twin-spar mono- coque chassis fabricated in ltaly byVerlicchifrom a blend ol aluminum shestand caslings. whosg only permitted modiftcation in FX mode is to hsve ths broadsr side panels of 6e Uvsses advsmurer tourersdded in orderto deliver iust undertttree Iit€rs more fuel, Ilat brings th€ tltal load up to 4.42 gallons.good snoughtodolhe Daytona 2m wif| three fuel stops. lf one of tle bikes had kept qoing long enough. "Allvre didwas add powerto lhe chassit" says Anderson, "aftfiough we wers allor,Ivod to rnodify itto givs o(tra fuel capacity, bscause ifs ourfueltank Eswellas ourfram€, and ths rules stats you can aherlhat O$eIwise,lhe Firobolt chassis was made to go racing." Well, itwas onc6lhsy'd added fullv adjustsble 0hlins racs suspensionfront and rear, but ifE true $atthe XB-RH l€me matches hs strostcoumerpan in being a triumph of packag- ing, a fact lhat Buell is iustifably proud of. "W€ hadto play3-D chess atconcept stage," he says, "iuslmoving eveq^hing aboutto be ableto installa 45-degrBeV-twin motorin a 52-inch wheelbase, wi$out comDromisinq our design obiectives." Thsso wors to produce 250cc GP-style han- dtng and steering geomsrry with a 2l-degree head anqle lorfie43mm ohlins forks, matched to 86mm ofrail- zmm upfrom the stock Firobolt - and a tiny l39l mm wheelbase. the traditional 45"degree a rchitecture ol all air-cooled H-D engines helped a lothore - with lhe design's inherentvibration in the absence of a balance shaft coumered bv rubb€tmouftingthe motor via BuellhtrademarktJniplanarenginemounts, featuring a trro of nonadiustablo, forqed linksfor $e localinq tie-rods that allow$e engine to be used as alully stressed chassis membet As on ths str66t Fire bolt, the separate oiltank is located not within the lrame butwithin tho tront lelt side of$e stock xBl2R cast-aluminum wraparound swinqsm made by Brembo.which operates the 0hlin6 camilovershock without bgnetit of a link. Three liters of lubricant are car. ried in the comparunent bshindthe pivot lto min- imizs adding unsprung weight), not inthe side arms flankinglhe tire. As Dart0fBuolfs "&D chess game,"lhis example of lateraltwo-Meeled design hought oflers the unexpsctgd bonus that $e swingarm acton helps remove aeEtionfromthe lubdcant and the oilruns coolervia $8 alloy c.sting sit' ting intha bresze- Ihere is, howEver, an oiltadia- tor on the lelt fiom fairing flanL ThE rgsutt iE not onlya mors rationalslxuc- trre, but 6lso I very stiff one, with a lowsr csfisr of gravity $an o$sr comparable bikes.Ihis, combined with fie carcfulpackaging of ttte ttlDle bike (includingdrs riderl, hslps med anolher of Buslll dssigntErgets on thE Freboh and its XB-Bfl spinolt sister: to reduce rs polar momem of iner- tia by positjoning tte center of mass of the bike as closs as possibl€ to the center of graviry. this mav sound arcaos, but is indeod a keylactor in GP chassis design - torreducing $s momsnt oI insr- tia in pitch and roll, as achie\.ed wifi rhe XB-RR, promot€s more predictable yet more responsiw handling.fianksro improv€d damping ratios on thg chassis and fuster roll r8tes. The choic€ of a singlo from brakB disc b slDp a bike weighing 370 pounds (wih oil but no tuel) helps achieve anolh8rof Buell'sgoals in reducing unsprung wEight to delive, improvsd suspsnsion compliance and rsducsd pitch.Ihe same Xrsmm Nissin tully florting. srainless-steel psrimstor disc is used here as on tho XB128 Firsbo&lvhich slso offsrs snhancsd steering delivered by its lowored Moscopic eftect bltis now combined wih a massivs €ight piston caliper especiallydevelopsd Ior$e bike. Buell'sown vEry liqft forgsd-magnesium Iront wfieel adds turher lo tho perimetsr discl dynam- ic qualifias, 6anks to $e fact $is is mountad on bosses close to $e rim, so tl8 brake forc€s are fed direcdy to t s {and rhus to the lirB}, rather $an to the MBsl spokes, which $erelore allows $s68 to be mado much lighter Even Pirellicameto$e 17 - ........ BUELL XB.RR ENGINE:....Air/oil-cooled olv 45-degree V-twin dry-sump four-stroke with two valves per cylinder, operated by pushrods DIMENSIONS:..-......... I 01.6 x 79.4 mm CAPACITY:.................................- I 339cc OUTPUI ..............,. 152 hp at 8000 rpm COiIPRESSION RATIO: ............ 12.5: I FUEUIGNITION: ....Siemem electronic fuel iniectioh and engine.rEnagement system with 2 x 62mm \+albro throttle bodies and single iniector per cylind€r TRANSITIISSION:....5"speed clore-ratio with triplex chain primary drive CLUTCH:................,...Hu|tiplate oil-bath CHASSIS: ....,.....Alumlnum mono

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