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/127556
; RIDING IMPRESSION 1993 Yamaha YZ125 &YZ250 ~ By Chris Jonnum Photos by Kinney Jones he 1992 season was without a doubt the most successful year that Yamaha has enjoyed in the world of motocross in quite some time; Jeff Emig captured the 125cc National Championship, bringing the factory its first U.S. National MX title in eight years, while Damon Bradshaw racked up a record nine supercross victories en route to an ever-so-close runner-up series finish on the Camel Supercross circuit. Meanwhile, Yankee Donny Schmit wrapped up the 250cc World Championship on a works Chesterfield Yamaha YZ250. To a company like Yamaha, wins on the race track translate into sales in the dealerships, and local tracks across America ha ve seen an increase in the amount of white and purple machines that carry the YZ logo. But has the knowledge Yamaha acquired during their succesful '92 season "trickled down" to the 1993 YZ125 and YZ250? T 6 What's new and improved? Both the YZ125 and the YZ250 have undergone considerable mechanical and cosmetic changes, so it is not surprising that both bikes have received price increases. Fortunately, however, the boosts are not out of line with the rise in cost of living. The YZ125 went up only $100 and costs $3699, while the YZ250's price tag grew $250 to a retail price of $4449. Last year, the YZ125 had a rightful reputation of being underpowered, though Emig prove<:! tha t the bike could be made to go fast. For 1993 it was Yamaha's intent to make the tiddler competitive in stock form. 1n an effort to accomplish this, they made several changes to the engine. Both the intake and the exhaust ports were modified, as was the combustion chamber, and the YPVS power valve's shape was changed as well. Crankcase pressure was increased, the intake tract was reduced slightly, and the angle of the reed cage, which features thicker reeds, has been altered as well. A low-boy expansion chamber replaces the traditional style of last year's unit, and allows more room for the larger airbox and air filter element. The new pipe uses a larger silencer, and a 15% larger radiator handles the cooling chores of the redesigned powerplant, which is secured with stronger motor mounts. Transmission and final gear ratios have also been altered, and the COl box was repositioned from the airbox to the head stay. In an attempt to provide a lighter clutch feel, Yamahaengineers decreased the clutch spring pressure by a claimed 7% and added one clutch plate and one friction plate, for a total of eight each. The push rod diameter was decreased from 15mm to 10mm, the oil capacity was increased and the shift forks' guide bar received an anti-friction surface (Right) The YZ250's motor features shong bottom-end and midrange power. (Below) Both YZS received all-new, narrower bodywork for 1993. treatment, all in an effort to ease shifting. Yamaha didn't limit their modifications to the engine, however. The rear shock cylinder's diameter was increased from 44 to 46mm, and the linkage is now tucked further up to allow greater ground clearance. The compression damping valve has been redesigned, as has the seal. Rear wheel travel has been increased to 12.8 inches, partly through