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/126818
The complex plumbing ofthe exhaust pipes on Honda 's latest V -4 is amazing. Twin -sparframe is simplerfor 1985; rad iator is V -shaped; hole in side ofseat allows fuel tap access. (Below) The mechanical drive for t he ATAC boxes is v isible ahead of the NSR500's dry clutch . South African Grand Prix Technical Review By Peter Clifford By race day in So uth Africa the works threecylin der Hondas were geared to pull 303 kp h or 188 mph even in the rarefied atmosphere u p at 6,000 feet. Tha t was calcu lated on static IQ. tire diameter and considering tire growth and the fact that th e bik es were pulling past th e optimum revs t1}e team t;x~teP them 10 be do in g well over300k. T his co u ld be true as the o fficial spe ed trap may not have been quite far enough dow n th e stra igh t but the fastest Honda th ro ugh th e trap was Didi er de Radigues' works tr ip le a t 293.86 kph or 182.64 mph. Spencer 's four was 7 kph slower and even Eddi e Law son's Yamah a was 2 kph down a t 291.21 kph or 180.99 mph. World Champion Lawson, though, wa s no t com p la in ing a bo u t the Marlbor o Yam aha. "I t's a better bike th an la st yea r," he sai d. " It seems to carbura re bett er but th e ma in improvement is in th e handling. It cha nges direction much bett er a nd I ca n gel th e power on th e road. The tires a re working good and it seem s to be a good sta rt, th ey reall y have improved th e bik e in th e a reas wh ere we needed it." The Yam aha s o f both Roche and Lawson as well as the simi la r Sonau to Gaul oi ses machine o f Christi an Sarron now have l fi-inch wh eels on the fro nt and 17 a t the back shod with Mi chelin tir es. Last season Lawson won on Dunlop tir es with an IS-Inch rea r a nd 17 or 18 on th e front. Yamaha ha s modified th e power va lve system on th e V-fou r a nd have a n ex tra bul ge in th e cylinder head. It looks as though th is is to enclose a larger guillot in e or a t least pl a ce the a xis o f th e slider parall el an d closer to th e cylinde r wall , thus making it mor e effecti ve. A look up th e ex ha ust port reveal s lar ger boo st ports en terin g th e tract fro m th e cyli nder eithe r side o f the ex haust port. KcI Carru th ers was very ret icent abou t cha nges to th eYamah a, o n ly commenti ng tha t th ere had been a dva nces in carbura tio n, T here is a ban k o f four Ila t-stide carb chokes cas t in only lWO segments boiled togeth er bel ween the center cho kes, making a very compact un it, Kel was hope ful th at with th e internal developme nts th at h ave been mad e to th e carbs problem s lik e th e sligh tly o ff performance a t Paul Ri card last year will be avoi ded . Whil e the new 0\\'81 Yamaha differs very little in th e la yout of fram e and sus pe nsion to last year' s 0\\'76, th e V-Io ur H onda is very dif ferent. Now with th e petro l lank back on top of th e en gine Spencer reported th at is a much bett er ma chine to ride. " It is much ea sier to get it from one side 10 the other, it feels com p letely different. It seemed lik e on the old bi ke with th e gas underneath th at it was lik e having a heavy roc k on the end of a lo n g stick. It was very difficu lt to control. Now I have the weight of th e gas much closer to me. You can 't sto p th e gas slos hi n g about completely a nd with it a ll down low it just seemed to push the front wheel a'Y~Y· Typical ~a~J~IY [all at Don ingv,