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/128219
YZ450F What Yamaha Says... What Was Done and Wh YZ125 YPVS (Yamaha Power-Valve System) power-valve system tuned to open slower and stay open longer from 8000 to 9000 rpm to broaden the powerband All ports raised .2mm Carburetor piston valve had singular .8mm bypass port before; it now features three .7mm ports for improved throttle response Smaller ignition coil with increased voltage Pipe body length increased 5mm to enhance low-end power Silencer diameter increased 1.6mm to improve low~end power 9mm smaller shift-pedal to better accommodate bigger feet and to reduce weight Chassis: (For all·chassis changes. see "Shared Changes") YZ250 Thinner frame gusset at the steering head with new shape; WR-shared frame boss eliminated to reduce weight VZ450F Clutch-wire routing changed to provide a lighter feel Newly designed clutch push-lever arm to accommodate new routing New clutch basket kick-pinion gear driven for smoother clutch engagement Thinner throttle wire for improved feel and lighter weight Oil hose changed from steel to aluminum to reduce weight Shared Changes [YZ125 AND VZ25J: Clutch-cable diameter lessened to reduce weight Aluminum steering and ring nuts now used to reduce weight Weight-saving aluminum radiator fitting collar now used VZ250 [ALL YZSJ: Steel cap added to end of YPVS for improved reliability Aluminum muffler-stay is now lighter Rubber cover added to COl unit to protect it better during washing Overall engine remains almost completely unchanged Newly designed front-brake master cylinder with internal fioat cap and new diaphragm to maintain braking consistency New triple clamps (for bigger fork) with "factory" surface treatment Bottom triple clamp tightening point changed to rear side to increase rigidity New front-brake cable guide "Kashima Coat" for gold "factory" look on outer fork tube Inner fork tubes increased from 46mm to 48mm Hydraulic fork bottoming system and heavier fork springs New-compound front and rear Dunlops Footpegs now made of lighter titanium and have added spikes for improved boot grip New self-locking shock bolt; only one tool now needed to remove/replace shock bolt Seat now has a no-slip cover on the sides Aluminum fork-guard collars used to reduce weight VZ250F Thinner throttle wire to reduce weight and improve action Grommet added to hold fuel breather hose in steering stem Cylinder body and crankcase feature larger cutaways to reduce pumping loss (down·stroke compression) for improved midrange and to reduce weight Oil hose changed from steel to lighter aluminum Ughter and stronger titanium header pipe and boot guard used now cue I e n e uv s JUNE 18, 2003 61