The revolutionary Yamaha YZ450F has been the most advanced machine in its class since 2010 thanks to a rearward-slanted, reversed engine design. This year, engineers made slight modifications in order to improve its jumping ability and handling over bumps. They also revised the ECU for greater control and throttle response under acceleration, while meeting CO2 and noise standards.

The 2012 Yamaha YZ450F comes out of the factory more race-ready than ever. New engine maps make for increased responsiveness, a fatter midrange powerband, and the same spirited performance at higher revs.


Mechanical revolution
The unique powerplant features a rearward-slanting cylinder that is reversed compared to traditional designs. This allows a straight intake system which maximizes power output, as well as optimized mass centralization for excellent handling and a light feel.

The front-positioned intake means that engine heat will have less "heating effect" on the incoming fuel charge (cooler fuel helps increase power). It also reduces the length of the exhaust system, which brings the rear shock closer to the bike's centre of gravity. Finally, this new setup allows more effective weight transfers and, in turn, more explosive acceleration. On the track, you can easily lift the front wheel to glide over bumps and increase rear tire grip.

You have to be in good shape and weigh at least 75 kg to start the engine of the 2012 Yamaha YZ450F. At 68 kg, I couldn't do it. A manual or automatic decompressor would be a welcome addition to this high-compression, large-displacement engine. After all, a kick-starter/EFI combo always requires a number of kicks to come alive.

On the track, you can easily lift the front wheel to glide over bumps and increase rear tire grip. (Photo: France Ouellet)

Rigidity and agility
The 2012 Yamaha YZ450F is built on a compact "bilateral beam" aluminum frame that's stiffer, lighter and more balanced for exceptional handling. The only problem with most aluminum frames is a certain lack of lateral flexibility, which is so important when powering out of corners. This one, though, provides great feedback at all times and lets you know if you can push a little harder.

The heavy feel of the previous generation has completely vanished. The 2012 model proves lively and nimble, perfectly steerable and a lot more athletic up in the air. The centralized mass plays a huge part in that renewed spirit.

In terms of ergonomics, the extra-wide footpegs provide excellent grip and help you shift your weight around. The firm, nicely sculpted seat makes it easy to slide fore and aft while providing decent comfort for a competition dirt bike.

The 2012 Yamaha YZ450F is built on a compact "bilateral beam" aluminum frame that's stiffer, lighter and more balanced for exceptional handling. (Photo: France Ouellet)

Flying over bumps
When attacking a track, the 2012 Yamaha YZ450F flies over bumps, tire ruts and mud holes without complaint. It maintains a straight line both under acceleration and while braking. The powerful, progressive brakes are beyond reproach.

The ultra-stiff Kayaba front fork and rear shock are designed for the worst terrain, yet they fare pretty well over small obstacles and irregularities. I definitely wouldn't call them comfortable, but they strike a nice balance between ride and handling.

Having said that, when I tested the machine on an excessively hot summer day (36 degrees Celsius), I noticed a relative deterioration in the rear shock's ability to soak up bumps due to the close proximity of the exhaust manifold. One quick fix is to install a sheet of asbestos wrapped in reflective aluminum paper.

Bottom line
The 2012 Yamaha YZ450F is a formidable weapon for skilled riders as it's fully committed to delivering superior performance on the track. Forget about picking up dead leaves around the cottage; with a demanding, yet highly capable, dirt bike such as this one you may just become the next great motocross star!

Pros
Revised ECU ensures greater control and throttle response
Unique engine design allows superb mass centralization
Powerful, progressive brakes

Cons
Rear shock feels the heat of the exhaust manifold
Engine is hard to start (especially when hot)