– Motorcycle News, Editorials, Product Reviews and Bike Reviews

Motorcycle News, Editorials, Product Reviews and Bike Reviews

Ty Davis Proves YZ450F Gearing Can Work Well Off-Road

We don’t normally write about the AMA National Hare and Hound series, but our familiarity with Yamaha’s 2003 YZ450F made the seventh round of the 2002 championship series interesting for one reason.

Riding 2003 YZ450Fs (yes, the four-speed motocross model, not the five-speed WR expected in a month or so), Ty Davis and Russ Pearson finished first and second at Lucerne Valley, with Davis clinching the championship with one round remaining.

Last year’s YZ426F was well respected as an off-road machine, not just as a motocrosser. This had a lot to do with the engine and the handling of the 426, but also its versatile five-speed gearbox that permitted respectable top speeds without sacrificing a low-enough first gear.

Although Lucerne Valley has many high-speed sections, there are some technical sections, and Davis concluded the new 450, even geared fourteen percent higher than stock (permitting approximately ninety miles per hour top speed) left first gear low enough to be acceptable for the conditions.

After reading this in the Cycle News report on the race, we pulled out our handbook on the new YZ450F, and looked at the internal gear ratios versus last year’s 426. Indeed, the internal gearing shows that the four-speed transmission of the new 450 is nearly as wide as the five-speed transmission of last year’s bike. For example, fourth gear on the 2003 model is approximately fifteen percent higher than fourth gear on last year’s bike, with first gear equalized on both models. Again, with first gear equalized on both models, the new 450 would have a top speed only six percent lower than the 426 (assuming a similar rev ceiling).

Another example drives home the point. With first gear equalized on each of the bikes, and the 2002 426 geared for a 70 mile per hour top speed, the 2003 450 would top out at approximately 66 miles per hour. In effect, the 2003 YZ450F has a wide-ratio four-speed, when compared with last year’s five-speed transmission in the 426.

Combine this with the fact that the 2003 450 pulls much stronger off the bottom (see our first riding impression at the Lake Whitney motocross track here – where third gear could be lugged through slower corners), and you have a bike with gearing that works perhaps as well, or better, than last year’s 426 off-road. Interesting.

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