Quick Ride
Quick Ride
YAMAHA YZ400F Still a Thumpin' good time
WHO WOULD HAVE thought Yamaha's up-start YZ400F would win an AMA Supercross race in its first season of competition? And who would have thought the same four-stroke motocrosser could win nearly every magazine shootout? Or carry Doug Henry to the AMA 250cc National Championship? Is this the stuff of dreams? Absolutely, but it's all true nevertheless.
This year, Yamaha made a bunch of little changes to the super-successfiul YZ, most of which elude the eye. Among the obvious are the larger-di ameter rear axle and lightened hub, bigger rear brake disc and updated. graphics. Not so obvi ous are the 2 pounds painstak ingly removed through casting changes and smaller-diameter bolts. Even gas-tank thickness was decreased in the name of the almighty ounce. The rest of the chassis is es sentially identical, save for new suspension valving and stiffer fork springs. The problem with
a relatively heavy four-stroke, of course, is that the suspension has to be stiff enough to resist bottoming while remaining com pliant. When fitted with option al, .46-kilogram fork springs, last year's bike was the ticket. Now, in a back-to-back compari son, it feels dancy and harsh.
And whereas two-strokes skate around, the `99 YZ400F tracks well regardless of whether it's accelerating or decelerating. Compared to the chassis changes, the list of engine up-
dates-a lightened wristpin, re duced exhaust-valve spring tension and a new carburetor with altered fuel passagewaysseems short. Still, anyone accus tomed to the previous model will probably find the engine bouncing off the rev limiter. That's because it revs much more quickly than before, yet hooks up just as well. The car buretion is a bit lean until the engine is fully warm, but the liq. uid-cooled Thumper no longer hiccups in tight turns if it's run a gear too high. Now, best results are achieved by short shifting. That way, the rider can take ad vantage of the engine's consider able bottom-end and midrange grunt; using the ear-piercing, top-end scream is optional. • Is there anything wrong with the YZ400F? For one, it's still a little heavy. At 259 pounds full of fuel, the bike feels light until you don't want it to-like when you're crashing or are trying to load it into the truck! The twinpiston front brake is as good as you'll find on any 250cc MXer, but because it's fitted to a heav ier bike, a fast rider can tax it. What's more, the tank graphics only last about two weeks-or two laps if you wear knee braces, The YZ400F stands out be cause it's a highly competitive four-stroke amid a pack of tradi tional two-strokes. Does that mean it's right for you? If you'rc a Thumper fan, don't hesitate. Otherwise, ride one, preferably while a buddy times you with a stopwatch. That said, we're bet ting Yamaha will have a few more converts this year.
Jimmy Lewis
