Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125883
• r o .....y ra aylg ac Suzuki's RE-S rotary By Lane Campbell At an indicated 115 MPI-I in 100 deg ree wea the r. the tem pe ratu re needle is beginning to creep toward "1-1." Five riders , eac h one tuc ked in tigh t behind the massive inst rument nacelle with its pop- up ple xiglass screen . h urtle across th e sh im meri ng Cali fo rn ia d esert. the strange h u m of th eir un familiar m ount s to rn aw ay by th e win d b last . feel ing almos t no vib ra tio n o u tside of so m e chain whip. T he m otorcycles are Su zuki RE-5 ro ta ries . 475 po und ma chines powered by 50 0cc wa ter-cooled , single ro t or . Wankel engines. T h e m en are fou r mo to-jo u rnalists and on e Suzu ki factory test rider. They are trying to determine if the unique new rotary engine Suzuki is the wave of the future o r a n evo lutionary sidetrack in mo torcycle design . Th e mac h ines are sty led and marketed as fast touring bikes . and so far they were living up to that promise. The power band and the perfo rmance envelope of the R E-5 are like no other motorcycle. To ap proach what this machine will and won't do . you have to , talk of "performance envelope" as tho ugh it were an aircraft u nder test. constantly searching for reasons why it responds as it does. Not surprisingly, every " reason why" stems fro m the character of Suzuki's Wankel engin e, and how Suzuki chose to so lve t hree often co nflicting demands: perfo rmance . fuel economy . dura bility . Take du rabil ity . Tip seal wea r is a known bugaboo of Wankel engines. One way to li mi t wear is to limit ma xim um RPM. th er eby lim iting roto r tip speed to gain th e sa me be ne fit t h a t I imi ti ng pis ton sp eed in a con ve ntional e n gine has o n ring life . e' Suzu ki chose a red -line RPM zo ne begin n ing at 6 500. For performance co m bi n ed with eco nomy. a lean m ixture is called for. The lean er th e m ixture, th e gre a te r heat loads arc im posed o n the engine. and su dden ly th e des igner is between a roc k an d a hard plaee o n durab ility . To ge t what they wanted. Suzuki fo un d ou t early that air cooling wouldn't cu t it , Even the o il is circulated to cool the rotor. So the RE·5 is a relative ly slow-turning, water-coo led engine with a h i g h I y soph isticated two-stage carb u re to r (w hose action is not u nl ike the p rogressive four-bar rel pots on some cars) and a to rque curve t hat is esse ntially no t a curve at all bu t a plateau. It is "overdesig ned" de I ibe rately fo r rel iabili ty , though machined and assembled to almost "clean roo m" tolerances. and it is heavy. Vet it is also essentially co mpact , especially in terms of lo wer case wid th . T he ne t effect is a heavy mo t o rcycle that is sluggish fro m a stan ding start. but deceptive ly fas t o nce it is ro lIing. Ro ta tional inertia of the engine is h igh. ma kin g up an d down sh ifti ng necessa ril y slow and delib era te, as revs cli m b slo wly an d d rop slo wly. The tr an smi ssion itself is fault less and q uick . bu t tryi ng to beat th e e ng ine's ine r tia on ly creates a pot entially da m aging lurch . Vel o nce in top (fifth) gear , th e machine is de ceptivel y q uick , as it can be rid de n from un der 35 MP H to jus t ove r 120 MPH in t ha t gea r . A t any speed , rolIi ng o n th e throt tle is like twi st in g a rheos ta l. T he torq ue never varies. the thrust ne ve r varies . I t just keeps go ing fas te r until it ru ns o ut of wind . It fe els m os t at home c ruising in th e 75-85 MPH ra nge . and it ca n run all Packaged to sell. Styling and use of color are as good as most of the industry. and engine detail fin ish is sparkling. The dual discs are standard. and might) strong. day. even in blistering heat. at 100 ~IPH. Now for the sup rise. It co rners . When w-as the last tim e (if ever) you th rew a big 500cc single in to a c urve at I 10 ~IPH with t he throt tle hard against the stop? It 's almost like that. excep t this machine , due to its we igh t and its long wheelbase. doesn't have the ins tan t reflexes of a classic single. It takes muscle to lay it ove r quick an d p ic k i t up quick. an d it requi res yo u to conscio usly lead a comer. Technological tour-de-force. Fan at right is electric/automatic. works great when rubber seal doesn't foul the blades. Capscrew-studded cover at t op houses water pump; the two other housings are ignition and oil filter. Most of the oil is ci rculated for engine cooling. o il cooler is below main rad iator. Bu t o nce co m m itted it will lay over. lay over mo re, and never ground any thi ng , T here wer e a few pro blems. O f t he five bi kes, t wo develo ped speed wo b bles wh en st uffed hard in to a be n d at 1 00-p l us. O ne w a s a ge ntl e, hig h -fre q uency twi tch tha t was jus t a bit uns e ttli ng , the o ther was a h orren d o u s ta nk-slappe r that was do wnright frigh Ien ing. The re maining th ree tracked lik e trains. T hat nigh t we all got our heads toget her fo r a general critique to try to figu re the anomaly o ut. It co uld ..J ..J w 1Il Q. :; « o w z « oJ > 1Il o .. :r III o have been ti res , it co u ld have been loose: swingarm pivots on two of the b ikes. 'The factory peo p le will check it out. La te in the day all of the bikes cropped up with fuel starvation and overhea ti ng , Overnight the fac tory crew tore in to the fucl system . fo und bits of filter fibre fro m so me gas station's " final fuel filter" wrapped around the fuel strainers . On o ne of the machines . a rubbe r air seal aroun d the little automatic fan worked loose an d fell down be tween the fan b lades and the ho using, locking the fan up for t he du ration. In heavy traffic at 100 degrees, the fan is nee de d and it will come on if the blades aren't fouled . Thar's o ne detail part that may cha nge Q. ' - - -- Progressive. plen ty of feel. there 's enough savage power ava ilable to haul a 475 pound bike down from horrendous speeds jus t as quickly as the ti res will allow. At the c ri t iq u e session. one consensus emerged from all of t he press riders: Ninety percen t of thc poten tial when the m achines a rc released fo r full market will never ride as h ar d, as fas t as prod uc tio n. we did. no r will they be looking for the things we we re . Fo r them, the RE·5 is mo re t ha n adeq ua te. They will never In th e ev e ning's critiq ue session , th e factory eng ineers to ld us ho w we had do ne . We had ru n so me 34 0 miles at an average speed of just over 78 MPH. Fra n kly. we had th ras he d he ll out of those b ikes - Behind that curved. polished tube lu rks one of the most complex carburetors ever fitted to a massproduction m otorcycle. Oil reservoi r is healthy capacity for use as a heat sink . a nd fuel consumption ranged from 31 MPH to j ust over 39 MP H. At a s teady legal 55 MPH (ho rro rs) we ntig h t have ha d over 45 MPH o u t of them. The brakes are al most to o good. Th ey are m uch better than the tires. peg t h e speedo me ter, n ev er c o m e close to gro n nd ing footpegs. Ve t we a ll asked if, in the fu ture , Suzuki migh t co nsider a 'ports model. less bul ky . maybe 100 pounds lighter. wi th less "flywheel effect" to the engine's rotor. The Su zuki people looked a t each other in a meaningful way . and sai d "maybe . " For now, a t a sugges ted re tail of 2475. Suzuki has a ve ry marketahle - ite m . It is one of the few mo torcycles t hat tru ly qualifies for tha t much-ab used word "unique ." It is deceptively fast . vibrationless as a turbine. quiet at speed (though uncom mon l y th roaty at i d le), well- mannered a nd trac table o n the road. and it exhibits tre me ndous pe rformance poten tial . It is also a sophisticated instru m ent in a stone -axe world . T he fuel filt er problem was a surprise to the fac tory people, They are go ing to have to do a crash training program to dial thei r dea le rs in to the mainte na nce of the RE·5. The engine is assembled un der such co n trolled co nd itions th at if any thi ng major goes wrong, the de aler will sen d th e whole engine back to a regi onal service ce n te r an d u nc ra te a new o n e for the c ustom er's b i ke . Th e mach in es will be available in qua ntity by Jan uary . 1975 . Do n ' t app roac h t hem looki ng for a "Superbike" or for a better BMW, or for an answer to Honda's GL-IOOO. Th e RE-5 just do esn 't fit any convenie nt mo lds. It is differe nt. it is un iqu e . even , and at the price, it is very. very good . • 23