Cycle News - Archive Issues - 1970's

Penton/Hi-Point's Lectron carburetor test Results so impressive it hardly seemed possible. By Jim Gianatsis We were somewhat skeptical when Penton Imports asked us to supervise and report on the testing they were doing with Lectron carburetors. Like most after-market accessory items , the Lectron carb seemed like a gadget designed more to impress (in the same category as red-tipped expansion ch ambers and front fork reservoirs) than perform. Besides, good friend Gunnar Lindstrom , ex-Husqvarna engineer, tester and editor of Dirt Bike magazine. had just completed a Lectron carburetor test in their December issue . Gunnar had not been impressed with th e Lectron ca rbs, In rid ing sessions and dy nometer tests he found them to offer no signi fica nt improvem ent over th e orig ina l equi pme nt carbs on three popular brands of d irt b ikes. Pen ton Imports' general manager Larry Maiers told us th at Penton /H i-Point beli eves so strongly in th e Lectron ca rbs' performance that th ey're goi ng to use th em as origi na l equipment. first with th e new 175cc bike and wit hin a year on a ll other models as well . Hi -Point Accessories will also sell Lecrron kits for other brands of din bikes. The obvious expense of added on American-made Lectrons to Penton/ KTMs. already the most expensive d irt bike im ported into Am erica . ind ica ted that Penton rea lly feel s th ey offer a substantia l im proveme nt in performa nce over con vent io na l carburetors. We also knew that Jack and Tom Pen ton were usin g Lee trons on their pers onal bikes . We con sented to supervise th e tesr.ma inl y to see that it was don e honestly, a nd to see if adding a Lectron ca rbu retor was a wort hwhile per· formance modification . How it works The Lectron ca rb u re to r's design see ms to be com p rised of a number of good features found on other. fu el meter ing d evices. The J apanese Mikuni is acknowledged as the best mot or cycle ca rbu re tor th ese days, and from th e Mikuni design Lectron uses a fuel enriche ning ci rc u it for co ld starting a nd a d ual -float system for accurate fu el flow to th e metering rod . The en riche ni ng system a llows qui ck sta rt ing of a 'co ld engi ne, usu all y within three kicks. and a llows th e engi ne to re ceive a rich eno ugh m ixture to run smoothly befor e it warms up . The d ua l-floa t system all ows th e ca rbu re to r to function properly on rou gh terra in or steep hills, and will a llow th e engine to co nti nue to run without load ing up when th e bik e is laid on its side. Unlike co nve nt iona l motorcycle ca rbu re tors which use ro und slides to co nt ro l air flow , th e Lect ron uses a flat slide sim ila r to those used in fuel -inj ection systems for race cars. How mot orcycle ca rbs eve r got stuc k wit h ro und slides over the yea rs mu st be a case of not wa nting to cha nge a proven des ign . A thi n , flat slid e like th e Lee tron 's is definitel y a clea ne r design for a ir flow purposes than a round one .' An d there are non e of th e ha ssles of tryin g to tu ne a ro u nd slid e for pro per cu ta way a nd , ai r cus hio n hei ght -- ob viously some thi ng tha t has to be do ne to corrr-ct design 12 faults in th e basic metering system . The Lectron 's flat slide needs no cutaway. and full y op en ed it offers the cleanest air flow possible . Id le is adj usted in th e normal manner by rai sing or lowering th e slid e by means of an adjusting screw on th e carb body sid e. ~ The bore of a Lectron is not straight but tapers 2mm toward the slide. This produces a ram -effe ct. causing air to flow past th e needle , or fuel met ering rod ;;~ th e Lectron folks like to ca ll it. fa ster th an it would in a carburetor with a flat bore even though th e bore d iameters at th e needle or meterin g rod are th e sam e. A 36mm Letron would flow mor e a ir than a standard 36mm ca rb o .., T he most unorthodox pa rt of th e Lectron th ou gh . is th e fuel metering rod. While usual motorcycle carbs use a ta pe red round needl e working in conjunctio with a needle jet and main jet to co ntro l fuel flow. th e Lectron uses only a constant diameter round needl e with a preci sion cut fla t side to con trol fuel flow . While a co nvent iona l ca rbu re to r ha s as many as five pa rts (slide cu t. a ir cushio n height. needle. needle jet . a nd main jet ) that need to be adjusted for tuning. th e Lectro onl y has one . But for all its sim plicity. co uld th e Lectron work better? . Tuning th e Lectron is much eas ier tha n a co nve nt iona l carburetor once you understand the principals of th e metering rod. Idle and low rpm richness are adj uste by ra ising or lowe rin g th e metering rod which is threaded int o th e slide. Mid -rang and top -end richness a re adjus ted by ch a ngi ng rods. Rods a re labeled with a tw di git num ber. The firs t number in th e di gi t signi fies th e degree of top-end ric hness. whi le th e seco nd d igit sign ifies th e degree of mid -range richness. T he sma ller eac digi t is, th e leaner th e rod is. For exa m p le. a 41 ro d is leaner on top -end than a 5 1 rod is. While a 41 rod is the sa me on top-end as a 42 rod . th e 42 rod ha s a rich e mi d -range. It a ll m ay sou nd co m plica ted at first . but once you understand i becomes mu ch sim pler th an the more numerou s varia bles in conventiona ca r bu reto rs. How it performs Rather th an a ny sort of d yno test ing. Penton wanted to chec k th e perform ance .; the Lectron s by ac tua l ridi ng. T he testing would ta ke pla ce over a two d ay peri o with th e first d ay's test ing ta king p lace on a 1/8 mil e drag strip and th e seco nd day' testing on a motocross track . Helping -with th e test wer e Milt Collins and Sparke Edmons on from Lcctron , a nd Jack Lehto and Don Rosen e from Penton. " Wha t im pressed us a bo u t the hon esty of th e test was th at Don Rosen e enlisted th help of loca l riders from a ro und th e At lanta area to test th e Lcctrons on th eir ow bik es insteading of using T eam Penton rid er s. Each rid er selec ted was a n a u thorit in the particular bra nd of bike he ro de . Bo Bobbit , owne r of Cycle Spe cia lties. th largest Bulta co shop in the sou theas t, brou ght his 370cc l'ursan g . Howard Gilliam manager of Yamaha of Decatu r , a Ya ma ha a nd Hu sq var na dealers hip . broug ht , 360cc YZ and a 360cc H usky Aut omatic. Brad W a llace , pr oba bly one of the hott es Ex pe rt mot ocr ossers in t he Atl anta area, showed up with his RM 370 Suzu ki. J e Hill . ISDT go ld medalist a nd to p end u ro a nd hare scram b les rider had his 250c MC5 pent on /KTl\1. Frank Lamb . a n up a nd co m ing you ngs ter in end uros an,

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