Yamaha’s rebirth as a maker of competition off-road bikes is now complete with the release of the 2016 YZ450FX. This is a race bike of the type that, until last year, we thought we would never see from a Japanese company. It’s designed for cross-country racing and has no compromises to appease government agencies, meaning no emission equipment and sound output levels that are similar to those of the motocross bikes. Yamaha has been reluctant to go down this road in the past because it sends mixed messages. On one hand it’s clearly meant for trails, but on the other Yamaha is importing it under EPA and CARB rules meant for closed-course competition. In the real world, that means the bike is meant for GNCC-type racing. For true trail riding on public land, Yamaha will have a new WR450F that will be released later in the season.
From a mechanical point of view, the bike is very similar to the YZ450F motocross bike. But there are about a dozen very important differences. The biggest is the addition of the electric starter. To do this, Yamaha had to redesign the left engine case, add a battery and beef up the generator. The generator output is now 160 watts, as opposed to the YZ’s 95 watts. Along with that comes an increase in flywheel inertia and a whole new crankshaft. Yamaha redesigned the motor so that 100 percent of the reciprocating weight is now balanced by the counterbalancer; on the motocross bike it’s 88 percent.
The next big difference between the MX and the FX is the gearbox. The new bike still has a five-speed, but it has a 30 percent wider range. First gear on the MX bike is just a little lower than second on the FX. On top, the FX has a taller fifth. You would have to reduce the rear sprocket by four teeth on the MX bike to get the same result.
Yamaha completely redesigned the clutch to take the heat and abuse of off-road riding, and redesigned the radiators and shrouds as well. As far as the parts of the motor that make the power, though, Yamaha left the YZ stuff in place. It uses the same head and piston and has only slight differences in the cams to work with the electric starter. Obviously, the motor uses the YZ concept of a rearward slanting cylinder with the exhaust in the rear and the intake in front. This was originally done to intensely centralize the mass of the motorcycle around the center of gravity, but now it’s become sort of a Yamaha calling card. The only real differences between the tuning of the FX motor and the MX motor are all electronic. The ECU is completely different and the mapping of the fuel injection and spark advance are tailored to make the off-road bike smoother off the bottom.
In the chassis department, the FX has all the items that you would expect from an off-road bike–the same types of things that riders have been doing on their own for years. The suspension is softer, there’s a kickstand and an 18-inch rear wheel. Yamaha made a provision for a radiator fan (the same one that will come on the WR450F as standard equipment). A skidplate comes as standard equipment. Yamaha didn’t provide the bike with handguards or a larger fuel tank, leaving those items to the aftermarket. It’s worth pointing out, though, that the YZ450F has a larger fuel tank than any other 450 MX bike.
We have a little time on the YZ450FX already and are completely surprised by the results. It doesn’t feel like a YZ. If you’ve ever ridden a YZ450F off-road you already know it’s a brute. It has a ton of power, even by the standards of the 450 MX class, but that isn’t the real problem. It’s a very lurchy bike. When you chop the throttle it’s like throwing out and anchor, and when you gas it, the bike is very abrupt. The FX has better manners. You can roll the throttle on more gradually and meter out power as you need it. The bike can be ridden slowly. It has a little less engine braking and that low first gear makes all the difference in the world. If you do the math, you would have to add 14 teeth to the rear sprocket of the YZ to come up with the same overall ratio that the FX has in first.
But you still need to keep in mind that this is a 450cc racebike. It makes a ton of power. You could race motocross on the FX and pull just as many holeshots as you do on a YZ450F. It tapers off earlier on top than the MX version because of the difference in mapping, but it makes so much power by then that most riders would never even notice. As a result, even the FX is a little bit of a handful on tight trails. Quite simply, it has more power than anyone really needs. Even if climbing gigantic, vertical hills is what you love most, the FX is overkill. You’re much more likely to loft the front end and steer into the weeds than actually run out of power.
Aside from being really, really powerful, the Yamaha is massive. With the electric starter, battery, generator and all that, it comes in about 15 pounds heavier than the motocross version. And if you remember, the YZ450F was never accused of being especially nimble. The one thing that makes the FX’s mass manageable is incredibly good suspension. The fork, in particular, is right on target for off-road riding. So despite the weight and despite the power, you have a very forgiving overall package. It’s very easy on your arms, even in rough terrain. The clutch pull is also very light and the brakes are surprisingly powerful, so when you factor in all those things, the Yamaha is a gentle brute that you can ride hard and long without wearing yourself down.
The YZ450FX will sell for $8890, which is about $300 more than the motocross version. The electric starter alone is worth every penny. We’re still riding and testing the FX, it’s going to be fun to try different fuel maps and ignition curves with the help of the Yamaha Power Tuner, which is one of the easiest EFI tuning tools on the market. Stay tuned for updates.
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