Photos By Adam Booth
Yamaha has been incredibly busy over the last year creating two very new motocross bikes, and this week we got our hands on one of them. While the ’14 YZ450F looks similar to last year’s machine, there are very few interchangeable parts. After a day at Zaca Station with the new blue beast, here is our first impression:
The heart of the YZ450F retains its previous year’s rearward tilt, but the significant internal changes are plenty. Working from the top to the bottom, the air box (which is directly above the engine) has grown in capacity by 265 percent increasing power in all RPM but especially the top-end. The sucking noise from the airbox area is much quieter than the 2013. We noticed we could pull a bit longer in second and third gear before having to up-shift. Both intake and exhaust ports have different shapes from last year and the valve sizes have increased from 36 to 37mm on the intake and 30 to 30.5mm on the exhaust. The piston changed to a flattop style and acquired a friction-reducing surface treatment. Yamaha wanted to provide easier to use smooth power and while the ’14 is less jerky off idle it is still pretty jumpy. We changed the mapping, adding some feel and taking out some ignition timing from zero to quarter throttle. We also went up to a 50-tooth rear sprocket, which let us use third gear the entire track. Overall we were able to make the YZ450F a little more user friendly.
In the transmission, the shift forks have changed shape along with new floating shift bars, larger diameter shift shaft and beefier shift lever all aimed at smoother, quicker shifting. When compared to last years model, clicking through the gears is slightly easier and the shift lever doesn’t have to move as far to engage the next gear. Inside the tranny, third is shorter than the ’13 YZ450F’s creating a shorter gap between second and third gears.
The YZ450F’s frame is all-new though similar to last year’s model, though out on the track, the bike feels shorter axle-to-axle. This is because the head tube is moved back 10mm and the rear wheel sits a little further forward in the swingarm due to a 49-tooth rear sprocket instead of last year’s 48. The primary gear ratio is changed to coincide with the 49-tooth sprocket so that the final gear ratio is the same as last year’s. The aluminum spars are hydro-formed allowing for different tube-wall thicknesses depending on where certain sections of the frame are located. With only one day and only one track we felt the suspension changes were an improvement on from the ’13 but when the throttle was chopped the front end seemed to still dive. Overall there is good comfort in the suspension and we will continue to work on dialing in the clickers and sag. We ran between 104mm and 100mm for the day depending on how loamy the track was.
Instead of the corkscrew-like exhaust pipe that graced the previous year’s YZ450F, the ’14 features a wrap-around exhaust that further centralizes mass and brings the relatively heavy muffler closer to the middle of the bike. This shorter in length muffler allows the asymmetric sub frame to be shorter. The pipe side has a very acute angle to the spars while the chain side has a wider angle.
Yet another way that Yamaha found to centralize mass was to move the already low gas tank even lower thanks to its unique two-part seat design to allow access to the gas cap. The new tank carries more gas (1.6 to 2.0 gallons) yet the fuel pump now sticks out the rear of the tank in a seemingly vulnerable position, though Yamaha hasn’t had any problems in that area. A new upper triple clamp features four bar positions and the handlebar mounts are now rubber mounted.
Overall, the 2014 YZ450F is the second generation of Yamaha’s airbox-forward, backward-exhaust design and though its newer design springboards off of the previous models, many of the 2014’s integral systems have changed. Whether those changes lead to victories is yet to be seen, but what we know for sure is that we won’t have any excuse for not sliding up high on the YZ-F’s tank any longer.