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
o 00 c::J') 1"""'4 (Clockwise from top left) Laurens Offner holds the LOP·modif ied shock reservoir, made from a '79 Yamaha monoshock. The Greek found the bike light and easy to control. Twelve inches of suspension travel calls for a tall crate , Enlarged to 493cc, the motor offers a good powerband. Weight is 206 Ibs. 18 not like it had two hours of practice and racing on it. Third and fourth are the working gears , and you almost never hit anything as low as second. The engine is so smooth, and the powerband so wide , pulling down to 2,000 rpm in the corners and th rot tling my way out without the clutch I found I could al most use third gear all around the track except for two of the longer straights where I got to click into fourth gear for a few seconds. . Fast? Yes. But the powerband is so deceptively smooth and wide, pulling between 2.000 up to over 7,000 rpm that there are no radical power surges to scare the rider. The rear 4 .50 Metzeler tire does a pretty good job of hooking up despite its seemingly mini mal size for the task it is presented. and bringing up the front without breaking the rear wheel loose is an easy thing to do. The only time you have to . really be careful with the power is on jumps where the usual quick throttle blip to bring the front end of the bike up is more than enough to flip the bike over backwards. Just remember never to use more than one quarter throttle anywhere on the track . . . any more and you better be parked in the pits with the engine turned off and the transmission in neutral . . . or else you're bound to get in trouble. The engine isn't the 493 's only strong point. To go fast with any kind of control requires excellent suspension and the 493 has it. The front forks are 38mm air/spring Simons with magne· sium sliders. reworked damping and 300mm of travel. Marty likes a mixture of different weight Yamaha : fork oil to attain 7!r.! weight which works best for him. The complete fork assembly has been reduced in weight . and rigidity has been increased through the machining of a special aluminum steering stem to replace the stock steel stem . Lighter triple clamps with do uble pinch bolts complete the modifications . The rea r suspension has 'received just as much attention. The swingarm is stock Yamaha. but the Monocross shock unit has been re;"orked with White Brothers valving and special three-weight oil. The shock is lightened internally with aluminum bushings and va lves. while outside th e steel pivot mount bolts are exchanged for titanium . The shock's remote framemounted deCarbon reservoir unit is actually the body of last year's F model shock which has been machined down to a smaller size , but offers much more air/oil capacity than this year's G model reservoir to prevent overheating. Laurens says that LOP is in , the process of manufacturing a similar reservoir assembly for sa le as a bolt-on. kit. The stock shock body has had additional snap ring grooves machined into it so a longer two-stage spring assembly can be used, consisting of the stock YZ sp ring and an extra firm IT spring. With shock modifications. the rear wheel travel is increased to 310mm . On the track , the suspension proved to be very soft just like many of the better prepared factory bikes. Sitting on the bike finds it sagging some 4-5 inches into its travel. On medium-size bumps and even in la rge whoops the bike can bottom out severely, while damping rebound is so light the bike literally bounces back up into the air after landing. The reason for such soft spring rates and light rebound damping is that the suspension will respond quicker in rough , high speed sections of a track. Soft spring ra res prevent the bike from kicking and bucking , . whi le quick return damping allows the suspension to recover in time to absorb the next bump. Having the bike settled so low in its suspension also has an obvious advantage in corners , making the bike lower and easier to control. What has been done is that the suspension is tuned for the majority of track condi tions to make the bike easier to ride with less fatigue , causing some sacri fice in handling performance for bigger bumps and jumps . A much better compromise than tryi ng to tu ne the suspension to cope with every track condition. causing an even larger sacrifice in overall handling performance and an increase in rider fatigue . In addition to the weight saving measures already pointed out , a ll the titanium and aluminum used in the suspension . there are even more light· • weight goodies int he. rest of the bike . Nearly every bolt and n ut in the frame and engine is made of titanium . Wheel hubs are special sand cast mag· nesium OW units from the Yamaha race team , laced up to stock spokes and D.l.D. rims . Renthal aluminum handlebars and even a works Suzuki R N aluminum kickstarter lever have found their way onto Marty's 493 . It is a fact that Laurens has a lways p rided . himself in trying to build the lightest production. based bikes possible. With the 493 though. Laurens has gone beyond that to the point of building the lightest Open class bike in this year's Nationals. a bike that is even lighter than the traditional'Iight factory Yamaha OWs and Suzuki RNs. How light is ligh t ? Even lighter than most factory 250cc works bikes. The 493 weighs only 206 po unds , well under the weight of the stock Yamaha YZ465G which is 230 pounds . For the Carlsbad Grand Prix. Laurens had to replace most of his lightweight parts to get the bike back up to the FIM's new minimum weight for the 500cc class at 224 po unds. The LOP 493cc Yamaha is in every way ... engine performance , handling. lig ht weight . . . as good or better than a factory works bike. And with Laurens Offner turning the wrenches, it has also proven to be one of the most reo liable bikes on the Nationa l circuit. All that was needed to prove its worth was for Marty Moates to win the United Sta tes G rand Prix at Carlsbad with it. •