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/126786
w w ~ Ul W II: X W II: 0 ! z z <{ ~ 0 II: III ~ w -' ~ 0 <{ 00 ..... eN' ..... > III Ul 0 I0 ~ ~ lL .... (1) ..0 S (1) ..... 0. Johnson's Yamaha looks sto~k; but it isn't. The major differences are the front disc brake. Ohlins shock,_porting and the long rod kit. (1) en Modifications made to Rick Johnson'" YZ250L Yamaha are not kept secret; almost every'trick is explained in the Yamaha Wrench Reports. The e.xhaust pipe is made by Stuart Toomey, while the silencer will come stock on '85 production YZs. The original frame is slightly modified. NationalChamillon RickJohnson's Yamaha YZ250L o e lie By Kit Palmer When Yamaha announced there would be no works machines for the 1984 motocross season, many people were skeptical. Instead, said Racing Manager Ken Clark, Rick Johnson, Broc Glover, Ron Lechien and Keith Bowen wouid ride production-based '84 YZs. Lechien didn't like that idea 16 much; shortly aher signing a contract 'for a factory ride with Yamaha during the 1984 season, Lechien left to ride works Hondas. He didn't feel the Yamahas would be competitive. As it turned out, Johnson and ex-teammate Lechien diced for the 250cc National Championship - production-pased vs. works. Johnson won. The big,question is, what does "production-based" really mean? To find out, I met Johnson's mechanic, Cliff Lett, at DeAnza Cycle Park four days after Johnson and his YZ250L crossed the finish line at Washougal to clinch the 250cc National Championship. The bike was untouched from the time Johnson rode it to the time I saw it, ri~ht down to the dirt accumulated at Washougal. Johnson's Yamaha is not box stock: it's not even dose. However, nearly every modification made to Johnson's YZ can realistically be duplicated by a YZ250L owner. To increase top-end horsepower the motor was ported. Porting specs used are the same ones revealed in the Yamaha Wrench Report mailed to every YZ250L owner; the only extra porting on Johnson's bike is thauhe intake chamber was widened by one millimeter. However, Lett feels the large intake chamber is too insignificant [0 mention in the Wrench Report. A long rod kit was installed to give the YZ a broader powerband. It doesn't increase horsepower. Johnson's exhaust pipe is made by Stuart Toomey. The Wrench Report says to cut away 5mm from the center cone and the header portions of the stock pipe. The Toomey pipe has the ., III e same specifications as a modified stock pipe, but without the reweld seams - the smoother pipe gives better resonation. Lett did not disclose the actual dollar amount of the pipe, but he did say they are very expensive.. On the end of the pipe is an '85 production silencer with a steel core. Lett says it is much easier to repack than a 1984 stock silencer. Johnson's 250 uses a stock YZ60 ignition. as used on Yamaha works bikes the past few years. Yamaha doesn't supply YZ250 owners with this information in the Wrench Report, because they don't always have enough YZ60 ignitions in stock; however, they are not trying to keep their use of YZ60 ignitions a secret, either. Lett says it's a "word of mouth" type thing, thaI if anyone asks, he'll tell them. He says the YZ60 ignition has the same curve as the stock YZ250 ignition, but has a heavier flywheel, producing less wheelspin and more traction, especially on hard, dry surfaces. Jetting is also the same as mentioned in the Wrench Reports. The only modification to the carb is the custom-cut slide. It now has a 2.75 e . cutaway - stock is 3.00. The intake reeds are 'the original steel ones. They have never been changed. Lett likes them because they work well and don't wear out or break, unlike fiber reeds. Johnson's Yamaha uses stock '82 YZ250J aluminum clutch plates. Lett replaces the plates every two weeks and the clutch springs after every race. He sayS Johnson likes to abuse the clutch. According to track conditions and layout, the transmission is changed for either an '82 or '83 transmission from the J and K YZs. Final drive gearing also varies. Stock has a 14tooth countershaft sprocket and a 53tooth rear. At Washougal, Lett switched the rear sprocket to a 54 to suit the long and steep uphills. Front and rear suspension has major changes. The stock rear shock is thrown out for an Ohlins shock, with a compression damping clicker (externally adjustment kpob), located on the reservoir. Lett installed a Simons Anti-Cavitatorfork kit on Johnson's YZ. Unlike the standard Anti-Cavitator kit, Johnson's has a new base valve for more