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/126478
It was at the Bel-Ray 500cc USGP of Motocross that a lot of other dazed and bewildered World Championship riders were asking the same question . Riders like 500cc series points leader Andre Malherbe, who wasn't used to being beaten off the starting line with his potent RC 450 works Honda , no r Brad Lackey whose monster 499cc Kawasaki Uni -Trak which held nothing in reserve du ring the second moro bailie with Moates .. . There was one big secret to th e LOP Yamaha wh ich Marty rode and even a couple of lillie secrets. The big secret I found out one weekday morning out on the Nationals when Marty and I went running. H e happened to let it slip out that his bike had its engine stroked out to 493ccl It was the biggest displacement, most potent bike in the Nationals. This running thing also left open all kinds of new possibilities for finding out secrets from factory riders when they might be left in a weakened physical condition. Immediately I arranged a test of the bike with Marty and Laurens Offner. La urens owns LOP Racing, an Illinois based accessory distributor and manufacturer of motocross products. But it is the racing team itself. and not the accessory company, which commands all of Laurens' attention. Besides serv o ing as owner, manager and whatever else , he is Marty's personal tuner and mechanic. This is the second season Marty has ridden for LOP , and it must be a strange feeling having the boss working for you . "W hen Laurens first bu ilt my bike for the Nationals , we took it out into this field by the shop and kept doing burnouts with it. We couldn't believe how fast it was. The rear wheel would almost never hook up. Just dig big trenches. Third and fourth gear starts were no problem. "Bu t then, the first week we took it to the Nationals at Mt. Morris the bike proved to be just too much. I couldn't control it in the corners it was so radical , and on the straights I wore myself out just trying to hold on to it." The following week was spent in .sting different cylinders with milder porting modifications until one with the right tuning was found . From that point on, Marty could be fou nd up at the front of the pack dicing it out with the factory riders every weekend . The Nationals leading up to Carlsbad saw Marty finishing eighth in Michigan, fourth in Georgia and sixth in Colorado. It was the confidence of racing on his own home turf at Carlsbad , though, near his home in San Diego that allowed him to snare both moto starts at the Grand Prix and carry the lead all the way to the finish line. Laurens remains silent about the modifications he has made to Marty'S engine, other than to admit the cylinder has been ported. The increase in displacement from 465cc to 493cc is a major machine shop operation requiring new crank flywheels , relocation of the crank pin further out from the crankshaft center line, and a new shorter rod. To help keep the power manageable even with the milder cylinder porting L au rens runs 2.85 dri ve gearing, the ta llest possi ble, arid fou rt h gear sta rts are still possible. T he increased to rque loading is hard on the stock Yamaha gea rbox causing the gears to twist and disto rt on their shafts. Nearly every race requires the transmission to be re built with new gears for t he following weekend. Riding the 493cc bike proved to be surprisingly easy. I rode it on the Atlanta Int erna tiona l Raceway rnotocross track right after the National and the entire bike a nd engine felt as tight and fresh as.if!t.were.brand,n~, • • o 00 (j) ..... Women's Motocross Nationals .... ""11 " 11980 I I~dress ~a I I II ~~~~:ur • WOMEN'S MOTOCROSS Pay badI to Pros Trophies to all other cl..... I .·a·~71\. \1 Name Rf. , , 1I , " 11 " 1' \1 ,_ ,, • \ 1 , 1 ":\': ' " JI . "I "I""t· . '1·, ~ l :I . , I. U91. race r. tor the racen." A ug. 17, Carlsbad , Calif. Age State I • =:~d 125cc - Zip ._ M~~~ Riding Class _ 'I .~·~ \ sponsored by Russ Darnell Motocross Schools -------..I NAT::':~ Carlsbad August 17 Club or Sponsor 250cc Each Event ;~~6 _ Total Plt-toots ie. Na me • Sports man OExpa rt ORidingnumber_ _ TOTAL _ _ . Send 2 legal-slza st amped ,se " -a dd re sse d enve Iopes t o: Vick ie Miller Heag ' 2167 EI Dora St. Lem on Grove•.CA 92045 - .-----(714) 4&2-9395 I I I I I I .J 17