From fright­en­ing to re­fined

How Suzuki’s two-stroke four de­vel­oped from an over­pow­ered hand­ful into a pol­ished world-beater

Classic Bike (UK) - - STARS’ BIKES SALE - WORDS: MIKE AR­MITAGE. PHOTOGRAPHY: BAUER AR­CHIVE

‘POWER AR­RIVED WITH THE SUB­TLETY OF A SIZE 12 TO THE GROIN’

The FIM an­nounced new Grand Prix rules in late 1967. These lim­ited the num­ber of cylin­ders in each class, and were es­pe­cially hard on small ca­pac­ity bikes. Hav­ing de­vel­oped a 400bhp/litre 50cc triple and 125cc V4 for ’68 that were ef­fec­tively ob­so­lete overnight, Suzuki (along with Honda) with­drew from rac­ing.

Pri­vate teams and im­porters car­ried on, how­ever, with larger-ca­pac­ity bikes based on Suzuki’s road mod­els: the TR500 was a T500 twin, the TR750 was the GT750 triple. Suc­cess brought in­creased fac­tory sup­port; for ’73, Jack Find­lay was a works rider and won the Se­nior TT, while Barry Sheene took the Shell Oils 500cc, MCN Su­per­bike and FIM For­mula One ti­tles. Smit­ten again with rac­ing, Suzuki then threw things into fast for­ward with a full-fac­tory GP re­turn and the leg­endary RG500.

RG500 SQUARE FOUR

Suzuki’s rid­ers saw the RG pro­to­type in Ha­ma­matsu, Ja­pan in early 1974. The new 500 was a wa­ter-cooled square four – think two par­al­lel twins, one be­hind the other. Mea­sur­ing 56 x 50.4mm, the 497.5cc two-stroke was ef­fec­tively four 125s, with four cranks geared to a cen­tral pri­mary shaft. Each crank car­ried a thin slot­ted disc to con­trol sup­ply from a side-mounted 34mm Mikuni car­bu­ret­tor. Front cylin­ders faced ahead with ex­pan­sion cham­ber ex­hausts un­der the en­gine, with rear cylin­ders and pipes fac­ing rear­wards. The tubu­lar steel frame car­ried an alu­minium al­loy swingarm and Kayaba sus­pen­sion, with 18in wheels. Disc brakes were copied from Lock­heed – odd pis­ton sizes (17.4mm and 19.1mm) were due to be­ing based ex­actly on their im­pe­rial de­sign.

The pro­to­type was wild, power ar­riv­ing with the sub­tlety of size 12 to the groin. Sheene took 1.5 sec­onds off the test track record with this mon­ster en­gine and over­whelmed chas­sis, later claim­ing the pro­to­type was more pow­er­ful than his cham­pi­onship-win­ning bikes.

Re­fined slightly (and de­tuned) for the 1974 500cc GP sea­son, the RG500 XR14 had 95bhp and was fast, but re­li­a­bil­ity wasn’t great; it ate pri­mary drives and gear­boxes, and of­ten seized. High-speed sta­bil­ity wasn’t ideal. En­gine nig­gles were ironed out for ’75 and Suzuki squeezed an­other 5bhp and 5mph, but Sheene’s hor­rific 175mph TR750 crash at Day­tona was rather a set­back... For 1976 the XR14 was much im­proved. New ge­om­e­try of 54 x 54mm gave 494.7cc, and power jumped to 114bhp at al­most 11,000rpm. Suzuki made it avail­able to privateers with a spec close to fac­tory bikes, though the of­fi­cial en­tries were vir­tu­ally un­beat­able – Sheene won half the sea­son’s races and took the ti­tle, and Suzuki rid­ers filled the next five places. A new RG at ’77 pre-sea­son test­ing had a ‘stepped’ en­gine (front cylin­ders lower than rear) and quick-change cas­sette gear­box; Barry wanted to race it, but Suzuki wanted to see what Yamaha had at the first round, so kept the XR14 with new cylin­ders and air sus­pen­sion (be­ing tested for the GS1000). They also tested a ‘big bang’ XR14 with all four pis­tons ris­ing to­gether (a mis­sile, but im­pos­si­ble to push start), but didn’t need that ei­ther – the Yama­has couldn’t stop the ‘old’ RG’S sec­ond ti­tle.

The ‘stepped’ RG did race in ’77, as the big-bore 652cc RGA700 in Su­per­bike and For­mula One. It reached the 500cc class as the RG500 XR22 in ’78 (pri­va­teer bikes were tagged RGB500), with 122bhp and 180mph po­ten­tial. The more com­pact en­gine al­lowed a longer braced swingarm for sta­bil­ity, and it fea­tured larger-di­am­e­ter forks and big­ger brakes. Suzuki had fewer works bikes, how­ever, and with Sheene off-colour Yamaha took charge with their ev­er­im­prov­ing bike and a mouthy Amer­i­can by the name of Kenny Roberts. Tweaks to the XR22 couldn’t stop Roberts tak­ing the 500cc ti­tle in ’78, ’79 and ’80. The third RG vari­ant ar­rived for 1981. The XR35 had raised com­pres­sion, larger 37.5mm carbs and 130bhp, a 16in front wheel for faster steer­ing – and Marco Lucchinelli of Gal­lina Suzuki Italia won the ti­tle. There was a new box-sec­tion alu­minium frame for ’82, and Franco Uncini (re­plac­ing Lucchinelli) claimed an­other cham­pi­onship for Suzuki.

The square four’s time was over, though. Suzuki was find­ing it harder to match Yamaha and Honda, so with­drew from com­pe­ti­tion in Oc­to­ber ’83. The fi­nal 25 pro­duc­tion RGB500S were made in ’84, and pri­vate and im­porter teams fought on. There were ex­per­i­ments with car­bon frames, and Dar­ren Dixon won the 1988 Bri­tish F1 ti­tle on a Pad­getts RG (the last stro­ker to win the Bri­tish F1/ Su­per­bike ti­tle). But its GP days were done.

RGV500 V4

Suzuki re­vealed the RGV500 XR71 pro­to­type and an­nounced their GP re­turn in Au­gust 1986. At 56 x 50.7mm its ge­om­e­try was al­most iden­ti­cal to the first RG, but this bike was ef­fec­tively two par­al­lel twins geared to­gether as a twin-crank V4. Cranks ro­tated the same way, re­quir­ing an in­ter­me­di­ate shaft, with banks of cylin­ders sat 80˚ apart. Mag­ne­sium carbs had reed­valve in­duc­tion, rather than disc valve, and an elec­tron­i­cally-con­trolled Power Cham­ber sys­tem var­ied ex­haust ge­om­e­try. It had over 140bhp at 11,500rpm, but the reeds and cun­ning ex­haust tech­nol­ogy gave huge midrange and smooth power – the new V4 was a huge step from the light-switch RGS.

‘THE 1989 RGV500 WON RACES BUT ALSO BROKE DOWN QUITE A BIT...’

The V4 raced in 1987 as the XR72, with im­proved cylin­ders and crankcases, Suzuki’s first twin-spar frame and Kayaba sus­pen­sion. Their test rider came third in the open­ing wet race and wild­card Kevin Sch­wantz was fourth in Spain, when con­di­tions and cir­cuits played to the V4’s midrange and ride­abil­ity; a lack of power, pace and re­li­a­bil­ity made the rest of the sea­son a strug­gle. Big changes for ’88 saw a heav­ily re­vised en­gine give over 150bhp at 12,300rpm with­out los­ing use­abil­ity, plus Showa sus­pen­sion. Sch­wantz (now full time in GPS) had four ros­trums but the RGV was still slow next to the Honda, so there was a new 160bhp mo­tor for 1989 with a 65˚ V-an­gle. Con­traro­tat­ing cranks re­duced vibes, and there was strong power from 9000rpm and a 13,700rpm limit. Chas­sis bal­ance was al­tered, Kayaba sus­pen­sion re­turned with up­side-down forks, and it got car­bon brakes. The RGV won six races, but also broke down quite a bit. Set­ting the Suzuki up was hard in ’90 and ’91. The new XR76 had al­most 170bhp and was much lighter, but be­came in­creas­ing fickle – rid­ers strug­gled with han­dling. When Honda in­tro­duced a big-bang NSR with close fir­ing in­ter­vals for ’92, Suzuki were the first to re­spond as they’d tried the idea on the RG. The new big-bang RGV worked bril­liantly, be­ing fast yet use­able – but crashes spoilt the sea­son. The break­through came in 1993. Rather than start the sea­son with a brand new bike, a win­ter of heavy test­ing ironed out is­sues with the ex­ist­ing one. Sch­wantz won the world ti­tle with the re­fined RGV500 XR79. Though they had a pol­ished mo­tor­cy­cle, Suzuki still had two is­sues: Honda, and their rider Mick Doohan. The Aus­tralian dom­i­nated the 1994 sea­son, win­ning nine out of 14 races and end­ing 150 points clear of Luca Cadalora’s sec­ond-placed Yamaha. With crew chief Jerry Burgess, Doohan won five back-to-back ti­tles – and with no-one else stand­ing a chance, de­vel­op­ment of other bikes slowed to a crawl. Suzuki re­grouped in au­tumn 1998. Sign­ing Kenny Roberts Jr and en­gi­neer Warren Will­ing (ex-roberts Sr) for the fol­low­ing year, they de­sign­ing a new RGV. The big-bang twin-crank 80˚ V4 had mag­ne­sium cases, so­le­noid-con­trolled power jet carbs, and two power valves: a guil­lo­tine, like Yamaha’s YPVS, and a ro­tary valve to open a se­condary ex­pan­sion cham­ber for torque. The 192bhp mo­tor hung from an al­loy frame with ad­justable swingarm pivot height, steer­ing an­gle, fork off­set and sub­frame height, with Showa sus­pen­sion. Roberts blitzed 1999’s open­ing rounds, break­ing Suzuki’s four-year win drought, and fin­ished the sea­son sec­ond. The next year his RGV500 XR89 won the cham­pi­onship, bring­ing Suzuki their last GP ti­tle and sign­ing off the two-stroke GP era on a high be­fore 2002’s four-stroke Mo­togp rev­o­lu­tion. Turn over for what the last RGV500 is like to ride

RIGHT: Ron Haslam wres­tles his 165bhp fac­tory RGV in the 1989 Bri­tish GP at Don­ing­ton Park

BE­LOW: Kenny Roberts and XR89, caught in har­mony at Don­ing­ton’s Mel­bourne Loop

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