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/128618
T h e other big n ew s is the WR400F g etting more m usc l e . It ' s now th e W R4 26F , an d it ta k es o n many o f the updates th at the YZ 4 2 6 F got la st year. As fo r t he 2001 YZ two - strokes , Ya maha made m a n y updates and refine ments to its already effe cti v e Supercross title-winni ng YZ I25 and 250. Some of Yamaha 's main goals with the YZS were to shave weight off th e bikes and to im p ro ve overall power and overre v, which Ya maha cla ims it d id . In th e c hassis d ep artm ent, Ya maha lig h tened and stre ngthened t h e YZ s ' fra m es, and also revam ped their suspension setti ngs and bottom ing sys tems. CN What fo llows is a li st o f ch anges to the 200 1 YZS: S c h ed uled Relea se Dates f or the 200 1 YZs and W R s : YZ80 •• •• . •• L a t e J uly YZ 12 5 • • . .. • L a te August YZ250 • . • • • . M i d -September YZ426F . • • • . La t e September WR426F • . • . M id -October YZ250F• . .•• Mid -Novemb er WR250F • •• . Mid -December (A b ove l Th e WR400F i s n ow the WR426F. (A bov e right) Titanium valves highlight the changes to the VZ 426F as well as the other of the VZ thumpers. (Right) The VZ250 and VZ125 (n ot shown) feature many refinements for 2001. List of Changes for 2001 PART WHAT THEY DID CLAIMED BENEFIT/ S Redesig ned End Cap To Match YZ 125 and 250 Shape and Cooling Rout e Changed Exh aust and Scavenging Ports Shape Changed Im proved Low -Speed Response and Increase Ov er-Rev YZ80 Exha ust Si lencer YZ 125 Cylinder Head Cylinder YPV S Po wer -Valve Valve Shape Chang ed/ Port Edge A ir -Tightness Im pro ved Crankshaft Assembly Diam eter 20m m Th inner Crankshaft O il Seals Diam eter 2mm Thinner/ Doubl e U p to Singl e U p Overall Diameter Reduced Six (formerly four j -Peta l/C arbon (forme rly resin)-Ty pe Connecting Rod/Small-End Bearing Reed Valve Carburetor (Mikuni TMX) Frame Increased Bore (38m m) Criti cal Ar eas Reinforc ed or Ligh t ened Improved Engine Coo ling Improved Low -End Pow er Reduced Friction/Power Loss Reduced Fri cti on /Pow er Loss Reduced Reciprocation Weight Imp ro ved Air Intake Effi ciency Improved Hiqh -Speed Power Imp roved Durabili ty and Reduced Weight YZ250 Crankshaft Oil Seal (ri ght) 34m m to 28 m m (single lip) Reduced Friction/Improve Low-Revoluti on Response/Red uce Hiqh -Revoluti on Horsepower Loss Crankshaft Assembly Crank shaft Shap e Chan ged/C onnec ting Rod Changed Reduced Fricti on Loss/Improved Low-Revoluti onResponse/ Reduced High-Revoluti on Horsepo wer Loss/Improved Relia bili ty Cylinder Head Volum e Chan ged from 22 .0cc to 21.5cc/Compression Ratio Up 8.8:1 to 9.1:1 Improved Pow er Character Cylinder Pis ton Wid er Auxili ary Scavenging Ports Cir -Clip Groove Positi on Chan ged Length Changed From 56mm to 53.5mm Im proved Throttl e Response All ow s for Short er Piston Pin to Ad ap t to New Cy lind er Reduced Recip rocating Weight Water Chann el Diam eter Increased Improved Coolin g Efficiency Reduced Weight Reduced Weight Improve Pow er Characteristic Imp roved Durabi lity and Reduced Weig ht Pist on Pin Wat er Pump Housi ng Cover Clutch Cover Transmission Shift-Cam Exhau st Pipe Frame Material Changed Fro m Alu minum to Magnesium Th ickness Reduced Ta per Sect ion Changed Certa in Areas Reinforced or Lightened YZ426F Intake/Exhau st Valves Valve Springs Crankshaft (ri ght) Material Changed From Iron to Titanium (40 % weight saving) Sm aller and Lighter Tr ansmission Sh ift-Cam Carburetor Thickness Reduced Hou sing/Absorber Spring/ Side Plate Redesigned New Setti ngs Exhau st Pipe COl Changed Header Pipe Bending An gle Changed Idling Ignition Ti mi ng Clutch Shape Changed/ Use of Keyways is discarded for Serato in Type/ Drive Gear Changed Improved Response Improved Response Reduced Fricti on Reduced Weight Improved Strength Improv ed Accelerati ng Pump Characteristics (more linea r) No Longer Needs to be Removed for Oil Filter Replacement Easier Start ing SHARED CHANGES YZ125/250 and 426F Sw ingarm For k s Stronger and Thi nner Material at Rear Arms New Setti ngs/New Bum p Rubber/New Ny lon Spacer Reduced Weight/Improved Suspension Performa nce Improved Ov erall Performance and Bottom Feeli ng Shoc k Fuel Tank/Fill er Cap Front Di sc Brake Clut ch Lever Lower Mou nting Sect ion Changed/Larger Bump Rubber) Fue ling Port Has Additional Filler Tube /New Inner Cap Seal Reduced Weig ht/Improved Anti -Bottoming Improved Reli ability Improved Brak ing Force More Knuckle Clearance Drive Chain Larger Di am eter (245mm to 250mm) Less Bend D.I.D (formerly Regina) /Height Shortened I m m Airbo x Join Material (ring) Changed Fro m Steel to T itanium Reduced Weight Reduced Weight SHARED CHANGES YZ80/125/250/426F Front Bra ke Seat Graphics Master Cylinder / Lever Adjustment Redesigned T wo-Tone New Reduced Weight and Improved Brake Ability Visual Visual , cue. e n e .... S • JUNE 21 , 2 0 0 0 17