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/126805
On the left is an RG500 racebike crankcase half with magnesium castings and titanium fasteners. On the right is an RG500 street bike crankcase half, with aluminum castings and steel fasteners. The engineering relationship is obvious. IS with the racer's 10. T he racer uses o ne rin g pe r p iston whi le th e stree t RG has two. Iron liners are used o n th e p roductio n Gamma , wh ereas present-day race RG s use a lloy cylinde rs with a lin ing of N ikasil. T he stro ke of th e 400cc pro to type is 54mm; th e 500 wi ll have a sq uare bore a nd stroke of 54 x 54mm in final prod uc tio n fo rm . T he new race R G s use a 56 x 50m m bore and stro ke, a nd according to Barry Sh eene, the latter con figura tio n produces superior pe rforma nce . Ea ch pair of cyli nders is bridged by a one-pi ece head. Inco rp o ra ted into the top end is Suzuki 's Automatic Exha ust Control (AEC) system , whi ch uses a rota ting va lve near th e exha ust port, as with Ya ma ha 's Po wer Va lve design , but works in p ractice more like H onda 's ATAC system . T he cylindrica l va lve si ts in a cha mber a bo ve th e exha ust po rt a nd a t midd le rpm ro ta tes 10 un cover a rectan g ul ar port th rough th e m iddl e of th e valve. T he port o p ens a passageway to a cha m ber th at is cast into th e cylinder head. The sys tem effectively in creases the vo lume o f th e ex pa nsio n cha m ber a n d thereby increases mid-ra nge ho rsepow er. • T he AEC va lves are ro ta ted bv bellcra n ks th at are ca ble o pe ra ted by a servomo to r loca ted beh ind th e steerin g head . T he servomoto r tak es o rde rs from sensors mounted in th e cra n kcase. Not ch es in th e left -front end a nd left -rear cra n k web s signa l the sensors. T h e AEC va lves ar e closed until 6,000 rpm. open full y unti l 8,000 rpm a nd th en close again . Cra n kcas e Iubricationis provided by a pump located on topof th e crankcase beh ind th e cylinders , a nd driven by an idler gear o n the starter shaft. The racer , of co urse, uses p remix . It 's exci ting to th ink j ust how closely the R G yo u' ll be able 10 bu y fro m your local dealer rese m bles th e R G yo u cou ld buy o n ly by mo rt gaging your ma nsion, You won ' t find th e lovely magnesium and tit an ium bits o n the p roduction vers io n that a bo u n d o n th e racer, but the mai n co m pone n ts a re just short of bein g ide ntical. The RG is more o f a tr ue GP replica tha n last yea r's sensa tio n, the RZ500. If it can match or exceed th e RZ's performance - as techn ica lly it appears ca pa ble o f - a nd if its ch as sis is u p 10 th e task, the Gamma co u ld be the terror of prod ucti o n racing in 1985. T oo bad it's not sched u led to be a vaila ble before th e sum me r. T he R G uses a n a lu m inu m fram e with a la rge forged sect io n su pporting th e steeri ng h ead tha t do u bles as the a ir bo x. The foa m filt er SI OI S in a t th e to p o f th e for ged cha m ber. a nd p las tic extensions conn ect the ra rb Two transmission assemblies, the rear one from the racebike, the front one from Ii street bike . Note the racer's longer clutch shaft to mount a dry clutch, and drilled shift drum . Street engine has extra shaft for kickstarter. (Below) Sand-cast racebike cylinder (on left) has more transfer ports and lacks AEC system chamber seen on the street bike's die-cast cylinder. Racebike has an o-ring versus street model's conventional head gasket. (Below) Racer's piston (on left) has a single ring to reduce friction, a large boost port, and a different wrist pin bearing. Street bike piston has two rings, no boost port. m ouths 10 th e bot tom of th e a ir bo x. It 's. a less co n vo lut ed path than th e int ak e system used o n th e RZ. .A la r ge . th in -wall ra d iator is ru bber- mo u nted 10 th e front o f th e fra me and co n nec ted 10 th e wa ter p u m p a t t he bo ttom o f the cra n kcase. Si n ce coola nt flows from the bottom of th e eng in e 10 th e cylinder h ea ds ra ther th an envelopi ng o n ly th e top en d , it a lso help s 10 coo l the cra n kca se. The sam e svstern is used o n th e RG racer. A th ermosta t o n the street R G ass ists warm-up. Expa nsion chambers fro m the fro nt cyli nd ers exit norma ll y u nder th e engine whi le th e rear two shoot a lmost stra ig h t ba ck under th e seat a nd exi t o n ei the r side of th e ta ill igh t. There are fewer kinks a nd deto ur s with th e rear cha m bers tha n a re necessary o n the RZ. T he p ipes-on this proto ty pe R G were hea vy ga uge steel ca pped with steel silencers, decora ted wi th a sleeve of a lu mi n u m. T hey weighed a IOn . We ex pec t th e product ion versions 10 be ligh ter, per haps wit h a lu m in u m silencers. As wit h th e RZ, th e p ipes a n d side panel s are in pla ces co vered w ith i ns u lati ng mater ial. R acin g RG s h ad a prope n si ty to fry th e rider; we ho pe th e prod uc tion version is less hostil e. Suzuki 's ro ad race bik es wert: the fir st 10 use the co m pa ny's Full Flo a ter rear sus pe ns io n. T he works bikes ha ve a forked pivo ting a rm wit h t w . str u ts 10 th e swi ngarm, as o n th e mot ocr ossers. T he R G uses a stra ig ht a rm with a single stru t 10 the boxsection a lu m in u m swinga rm . T h shock fea tu res h ydrau lic pre lo a adjustment but no da mpi ng adj us t ment. T he fork has 38mm sta nc hions with bot h a ir assist and da mpin adj us tmen t. T he twin front brak es shou ld be strong , wh a t wit h fourpiston ca lipers a n d IO- inc h di scs. T he floating rear brake uses a twin pi ston ca liper an d a 7-inch di sc. N ew design Brid geston e tires a re fitt ed t an 18-inch rear wh eel a nd a 16-inche a t th e front . An integ ral fork brac a lso sup ports the Iai red front fender. Th e o il an d coola nt ta n ks, w hi c o n th e RZ are located h igh in th fai rin g , a rc o n th e R G situa ted i more typ ical spots beh ind the en g ine T he battery si ts under th e rea r o f th ga s ta n k in fro nt o f the oil tank. wh il th e coola nt reservoir is j ust a bo ve th swinga rm p ivot. Suzuki took the sim p le approac to bui ldi ng its fir st street rwo- stro k s i nce t h e G T s of t he 19 70 s smoo t h ing the ro ugh edges o ff wo rks engine , addi nga kickstart sha ft oil p um p a nd a lte rnator. Indeed , th RG 500 shou ld we ll deserv e its ra cin prefix .