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/128160
What with all the attention given to the big YZF, Yamaha probably could have gotten away with leaving the 250F pretty much as is, especially since it appears that there will be no other quarter-liter thumpers ready for the '03 model year. Instead, the company has opted to shower the bike with significant updates, the most visible of which are the slick new bodywork (the new, lower tank holds about a quarter of a gallon less fuel) and airbox. In addition, the little YZF gets the cylinder cutaway that its big brother receives, as well as a redesigned crankshaft and a camshaft with an automatic decompression system (the decompression lever is replaced with a handlebar-mounted hot-start lever). The cam-chain tensioner is smaller to reduce friction, while the lower-rod bearing is larger. Moving on to the oil system, the oil-filter material is changed from steel to paper, the oil-filler plug has been relocated from the frame to the crankcase cover (there's still an oil-level plug on the frame, though it's lower), and the oil-circulation system is now lighter and more compact, like the 450's. The CDI magnet rotor and boss are now unified, the ignition coil is now integrated into the spark-plug cap, and the carb's throttle assembly is now sealed from dirt. The 250F's subframe now has square tubing, and the main-frame tubing is stronger. Yamaha completely reworked its two-stroke lineup last year, so '03 finds the ring-dings getting focused refinement rather than extensive overhaul. The 250 receives new cylinder porting (the exhaust port's radius is changed, and it's moved 0.4mm higher) and to match it, the head has slightly less combustion-chamber volume. The crankshaft taper is changed, and the transmission gets lmm-wider second and fourth gears (second is also slightly taller). The frame is also more rigid, thanks to a larger main pipe (though the cross-pipe diameter is slightly smaller). Like the two-stroke 250, the tiddler YZ gets increased cylinder-head volume (though the compression ratio remains the same) and reworked exhaust and transfer ports. It also receives the 250-type better-sealing exhaust valve, and its carburetor has a revised air screw. The intake manifold is straightened, the reed valves are thicker, and first and second gears are lower. The same changes made to the 250 frame are made to the 125, and VZ\25 owners will be able to get a heavier flywheel as an after-purchase option. mOD ~~ There are a number of changes that were made to the entire motocross line-up, so we'll enumerate them all here in one spot. The swingarms are all different, with a smaller axle end and an anodized treatment, the rear-caliper protectors are smaller, and the chain sliders are redesigned. On the binders, the front-brake calipers have aluminum pistons (instead of plastic); the front master cylinders are altered slightly; the rear calipers have a new design (with a different brake-pad area and a smaller piston diameter); and the rear master cylinder now has its reserve tank integrated (it also has a smaller piston diameter). VZ85 cue. e n e _ S • JUNE 26, 2002