Cycle News - Archive Issues - 1980's

~ Impression: KTM 420 MXC eReturn of the monster's little b~:~~::~;~~";drn,;al By Dan McCauley The 420cc KTM was first produced in 1979, but at the end of the following year the 420 was dropped from the Austrian firm's line. Why? Beca use KTM unleashed on .the public a n .O p en class animal tha t onl y a few m en have been able to tame. That bike. of course, is th e a weso me KTM 495. R ealiz- 14 in g the 495 " m an -ea ter" is perha p s a bit more tha n th e average d irt rid er need s, KTM has re-r eleased th e 495's " litt le brother " - thus th e return of the 420 MXC. T h e two machi nes sha re ma ny of th e same tra its with th e comparative ly m ild ma nnered 420 being th e more forgiving o f th e pair . Built with motocross soph isticat io n for maxim u m effec tive ness , th e 420 MX C ca n ru n w ith the best at the top o f the co m petitive world wh ile sti ll retaini ng th e a bi lity of being a fun toy to go trai l blasting o n . In fact, the 420 is the kin d o f motorcycle that can satisfy a wide variety o f riders, fro m th e basi c trail sq u id to a Na tiona l AA ra nked end uro star. ISD T · gold m edalist J eff H ill , KTM 's So ut heastern rid er representative, too k th e tim e to th or oughl y fa m ilia ri ze u s with th e feat ures, cha nges a nd qu irks of th e 420. Hill a lso mad e sure th e stoc k mach in e was runnin g p roperl y a n d th at th e suspen sion was dial ed in to best sui t th e 150 pound Cycle News tes ter. T he o n ly ch an ge we requested from stock was th e shorte ni ng of th e handl ebar wid th from the out-of-t he-crate 34 inc he s to ou r preferre d wid th , 31 in ch es. So, wi th a ll sys tems go, we took th e shi ny wh i te 420 to a h ar e scra m bles race to begin our test in g. With heavy ra ins having a lready turn ed th e san dy cent ra l Geo rgi a co urse in to a mud bo wl , we kn ew th e o ne a nd o ne-ha lf hou r race would be a good test bed wi th wh ich we co u ld determ in e th e stre ngths an d weaknesses, if a ny , o f th e bike. As it turned o u t, th e race proved very reward in g as th e KTM carried us to n o t o nly the Open class win , but o vera ll victory as wel l. What fo llows . is o u r impression o f the bike a fte r riding it to th at win, p lus smo king it over before and a fter the run . Wh en co ld, o n ly th ree or fou r good kic ks were needed 10 sta rt th e 420. T hat 's ap precia ted beca use so me big bore bi kes requi re th e ri der kn ow so me tric k, or be a ble 10 kick past th e point he's a lre ady blue in th e face. With the -120, yo u just tu rn on the gas, tickl e th e Bin g carbu retor until gas begin s to run o ut, crack th e th rottle a bo u t a quarter tu rn , kick it and bin go ! On o ne occasion th e kickstart lever got hun g u p undern eath th e swingarm a fter reachin g the bo ttom o f its stroke. Whik wr m enti on tha t, it's no big deal ber aus« a ll y O ll han.' to do is ben d o ver an d u n wedge it by hand . After th e eng ine is wa rm ed up , o ne kick would a lwa ys fir e it back u p after yo u' ve shu t i t down . We managed to fall th ree ti mes - for testing purposes, of co u rse - d uri ng th e hare scram bles, tw ice on some slick woods trails and agai n out in a fast section . The fi rst tw o times we wer e a ble 10 rem ount wi th o ut ha vin g 10 restart th e bike, but whe n we unload ed in th e fast sec tio n th e en gi ne na tura lly sto p pe d runn in g . A si ng le sta b a t th e ki ckstarter brought th e en gi ne right back 10 life. Measuring o u t to 4 19.6cc, th e co n venti on al tw o-st roke, p ist on p ort engine u ses a ra ther lon g intak e track and a five-speed gea rbo x. KTM claims 46 horsepower is being produced a t 6,800 rpm . T ha t's by n o means an o u trageous amou nt o f power co m pared 10 m an y o f toda y's bi g bore bikes, but more i m porta nt than just numbers is th e way in wh ich th e power is del ivered . And th at 's wh ere th e 420 MXC sh ines . Sm oo th , co n troll able p ower ca n be a tt ribu ted 10 so me wha t m ild po rt ing a nd a lso th e extern a l flywheel. Although i t certainl y wo n't diminish th e bike's performa nce , th e sil ver p aint o n th e powerplant is p ron e to flak e o ff. Un li ke man y o ther Open class bikes, the KTM 420 lacks a 'reed va lve. T he crisp runn in g MX C h a s enough power to be very co mpeti ti ve in a ny ea stern end uro. Deser t riders wi ll probabl y want more to p en d, and goi ng u p o ne toot h 10 a 16 toot h co u nters ha ft sprocket shou ld acco mplish th at. Clu tch p ull has been eased ove r ea rlier models, bu t still requir es more th an tw o fin gers. Lubin g th e ca b le o n a regular basis is a good idea , a nd wh en th e stoc k ca ble wear s o u t. man y KTM o wne rs go with a T erryr a ble. The38mm Bing ca r bu reto r doesn 't have a cho ke and a p pa rent ly do esn't need o ne as the tickl er does th e job just fin e. The ai r bo x ha s been impro ved by widenin g th e top for eas ier servici ng of the filter o nce th e sea t is re moved . A twin-stage Pol y T wo ai r filt er co mes with a ll KTM s. Draw in g a ir from under th e seat, th e MXC's ai rbo x is as to the uni t o n th e 495. A reb ui lda ble steel silencer comes stock while an optional U .S . Forestry Service approved T ra p p spark arrester is avail ab le fro m KTM . A R icht er a lumin um silencer or spark arrester may be a good way to remove a few extra o u nces . The 420 sports a n im p ro ved single down tu be, split cradle frame made of h ig h qual irv chromolv 25. T he tu bi ng d iameter of th e ma in fram e ha s bee n in creased bv 4m m wh ich allows th e KTM engi neers to decrease th e o verall wei ght of the frame by deleting a p iece o f th e su p p o rt tubin g which hampered access to th e ca rbo In 1982, KTM p rodu ced th e fir st modern da y era production bikes with removabl e rear su bfra me sectio ns - similar to th e wo rks H onda RC' s. The rem ovabl e sec tio n is handy as i t a llows qui ck access for tuning o f th e si ngle Fox T wi n Cl icker shock. New for '82 in th e sus pe nsion department is a 42m m Marzocch i fork. The beefy un it features forged alu mi n um sliders wh ich are ligh t as well as strong. 11.8 inc hes of reall y plush travel is p art ly d ue to improved damping characteristics. T he stock fiv e-w ei ght o il was n 't cha n g ed because the fork was spot o n th e wa y it ca me out of the bo x. . We ha ve hea rd th at the fo rk seems to " brea k in " a nd work even bett er as a sma ll a mou nt of fork sea l " sriction " goes away. Bu t as we just said, th e fork worked great fro m m ile o ne a nd we were im p resse d th a t th e fo rk sea ls d idn 't leak desp ite th e gruel ing race mil es we w ork ed th e bike th rough. Th e 420's P ro' L ever rear sus pe nsio n su p p lies o ver 12" of rear wheel tra vel. Ov er a foot o f travel for a bike th at is going to be ridd en in the woods is certai n ly impressive. A totall y adj usta ble sin gl e Fox Twin Clicker shock h andles the respo n sibil it y o f eq ua lizing th e performance supplied by th e front sus pe n sio n . To help with this ta sk , KTM engineers hav e co me up with an im proved , m o re progressiv e. leverage ratio by len gthen in!,: th e Pro Lever arm. The co n necti ng a rm H eim joints hav e Zerk fi ttings so g rease ca n be pumped in bet wee n co m p lete maintenance teardowns. The T w in Click er shock has 36 rebound a nd eig h t co m p ressio n settings. Rebound is adj us ted a t th e botto m o f th e shock sha ft wi th zero th e stiffest setti ng a n d 36 the lightest . T he shock came set o n 12 a nd we felt th at to be a bit too ligh t so we ran th e bik e o n 8. A large shock reser vo ir si ts behind th e ri ght pl ast ic side p anel. On top of the reservoir is th e compressio n adj ustment kn ob. KTM delivered th e 420 wi th th e co mpress io n set o n th e thi rd of eight setti ngs. We o p ted to cha nge it to lu cky number five. If th os e cha nges aren 't enough , the sp ring pre-l oad ca n a lso be adj us ted to a setting o f th e rider 's prefer ence. Out o f th e crate th e p re-load wa s a Ii ttl e o n th e soft side so we increased it by tighten in g th e lar ge shoc k sp rin g approximatel y 10mm. T heon ly thing we didn 't fool with wa s th e nitrogen pressure. 250 pounds is stoc k. A Celast o bumper is locat ed a t th e base o f th e shock to eli m ina te any possi bility o f ha rsh bottomi ng. Even after a n hou r a nd a half of riding o ver rough ter ra in, th e shock never bottomed o ut. .

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