Cycle News - Archive Issues - 1980's

l l Os up to l 30cc we run a 22mm Keihi ll (stoc k on a lID is l 8mm ), a n d a n yth ing from 130 to l8 0cc we run a 26mm carbu retor. Keih ins seem to run better d ue to the differen ce in the in ta ke pulse of a two-a nd four-stroke en gine, fou r-stroke bei ng th e weak er. Keih in s seem to be tai lored more to a four-stro ke;it will gi ve yo u a sm oother p ower ra nge, easier to jet, a nd yo u will not get a ny flat spots," adds Sparks. " Keih irr's may be a little expensive, but in the long run sho u ld elim inate an y headaches th a t you mi gh t encou nter by running , say, a Mikun i. " At o ne time Mikun i d id ma ke a good four-strok e carb ure tor, it wa s a 24m m desig ned for the XR75s back when th ey were popular. Bu t now yo u ca n 't get them ; that 's the rea son for the switch," Sparks remember s. Wh a t kind of horsepower d ifference is there? " Well as fa r as pea k horsepower , they a re about th e same, but o n a pow er cu rve - say Mik u ni was making six h orsepo wer at 3000 rpm - a Keih in wou ld ma ke close to seven oreig h t hor sepower at the same rp m. It wo ul d j ust have a fla tter power cu rve ; th e response is a whole lot better a long with greater low end." T he re is a nother wa y of testing your carb fo r jetti ng other than the meth od we disc ussed earli er. ·T ake you r three-wh eeler out a nd get plug readings a fter you ha ve riden your bike fora whi le. Todo this , you ma ke a co u ple of h ard pas ses - run it fro m a dead stop a ll th e wa y into fou rt h , then sh u t if off clea nly , coast to a stop, pu ll o u t the plug, a nd that will gi ve you a reading to go from . If the p lug is a ligh t tan co lor, tha t means it 's lea n , a nd if th e p lu g is da rk brown , that means it' s too ri ch . From the re, try to find a hap p y med iu m by changing mai n jets. For the 185s a nd 200cc bikes, Sparks claims, "There a re n o real secre ts. All the so-ca lled secrets a re tied u p in the head, It's just a matter of d oing th ings right as fa r as carb uretio n, ca m timing a nd a good exha ust system. A28 mm Keihi n is recommended for the 185 a nd 200cc bikes." There a re a lso so me ca rb cha nges whi ch ATC Performance Factory sells as a co mp lete carbu retor kit. Changes in clude changing the metering rod. T he rod ha s six not ch es on it , a nd there is a cli p which is usu ally in the cente r posi tion. Ra ising th e cli p lowers th e needl e and leans o u t the mi drange. Lowering the cl ip and ra isin g the need le will rich en it up. On Sparks' bike, he ra n th e clip a t the bottom. T hi s all ow s h im to run the mi d-ra nge rich. On an a ll o ut race r tha t ha s a modified race engin e, a 125 ma in je t is reco m me nded . If yo u 're go ing to bolt a carb ureto r kit on a stock engine , you would still leave th e needl e in th e sa me positi on a nd run a 120 mai n j et which, of co urse, is n ot as bi g. Ad d a K&N a ir filter , a n d you are ready to tea r th em up . Some specia l no tes must be taken wh en insta lli ng the modified ca rb uretor kit. It 's necessa ry to modify the th rottle assem bl y to mak e sure the ca rb ure to r slide o pens a ll the wa y. If not modified , yo u wi ll o n ly ge t a bo u t th ree-fo urths throttle. One la st item : If yo u' re go ing for the modified ca rbu reto r, it ma kes sens e to go one step fu rther. That is a n exha ust system; it's sorta like p u tting the icing o n th e ca ke. ATC Perfor man ce has develo ped suc h an exhaust system to co m p leme n t their carburetor kit : What yo u have now is a ver y reli a ble bo lt -on pa ckage full o f performance and fun . If yo u have a ny questions a t a ll, contact ATC Performance Factory at 89 12 Li ll y Street, La mont, CA 93241. or. ca ll iem ,805/845-3440. f r r, ATI' .... a. <{ CJ) ~. W Z ~ <{ GO RACING! Leave the spectating to the "talkers " The Jlationwide sport of Karting offers great racing in many forms: 130 mph on full-sized tracks like Daytona. Ontario and Watkins Glen ... or, i1 YOlllike the hairy, broadsliding act ion of a dirt oval, ". or maybe tight, precise, super fast actio~ and incredible 'acceleration -Karting's Road Racing, Speedway or Sprint divisions get you there at less cost and more racing than any other form of motorsport! The racing is any1hing but tame ... on local, nati.qnal or pro,essionallevels, Karting offers it all. YOU can DO IT, -like many of the biggest names worldwide wt'Io got into racing through Karting. There is Karting in your local area, right now ... GO RACING - IN KARTING! - - - - - - - - - I'm reaay to GO RACING. Here's $1.00, send me information on Karting , and the action in my general areal Name Address City State Zip ..,----:-----------------.... The manufacturers, organizations and retail stores of the Kart ing Industry Council welcome your interest. Send to: KIC P.O. Box 335. Dept. ATV Norco. CA 91760 Promote and Protec t Introducing the new ATV-2, a new maxi-sized windshield made from high clarity 3/16" acrylic sheet with all chrome mounting hardware. The ·ATV-2 is an easy mount full coverage windshield that adds maximum protection from wind , mud, ra in and underbrush. Will soon be available at all our fu ll line distributors. Retail for less than $60.00. '- DEPT. CN - P. O. Box 16212 Jacksonville, Florida 32216 ATV·2 lie on the., Does SUcceSS. other side of a b\g dune. Findo~t. OF"-"""''''' INCREASE FUEL CAPACITY 36% ~ith ~~ ATC GAS TANKS 3 * Front Suspension All Makes Made to Order * Hellarc Welding Aluminum & Steel * Cyl. Boring 512.00 Per Hole * Tri-Moto 125-175 Mods .~965 Stq. B_d U.lt B Sa.ta Jr. Sprl.p, CA906,o ---(:U~)II02-.'" • Equipped w ith right ang le elbow. mounting hardware and gas cap . • Contemporary sty ling. • Pract ically indestr uct ibl e. • Tight seal. screw-on-type gas cap. • Never requires pain t. one-piece red color molded. • LOW COST. Easy to install . ATC 250R 3.2 Gallon Tank - $99.00 Retail ATC 90. 110. 185S. 200 2.5 Gallon Tank - $89.00 Retail YOU N G ' S CYCLE SUPPLY DEALER INQUIRIES INVITED (213) 891·5619 (213) 891·5610 13

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