( 5) Chain guide/buffer. The chain buffer on top of the swingarm is now made from a higher-density urethane, while the brackets holding the rear chain guide in place are stronger. ( 6) Throttle cable. We noticed that the return throttle cable does not have an inline slack adjuster. Q: WHAT IS THE BIGGEST UPGRADE OF 2013? A: All the buzz revolves around the Kayaba Pneumatic Spring Forks (PSF). Replacing the steel coil springs with air means the PSF forks offer less friction, improved bottoming resistance, easier tuning and a 1.7-pound weight savings. The Kayaba air forks won’t set the world on fire, but they are better than the Kayaba AOSS forks from last year. Q: WHAT ARE 10 THINGS EVERYONE SHOULD KNOW ABOUT AIR FORKS? A: Unless you raced motocross from 1974 to 1979, you will have little or no experience with air forks. There are 10 things you need to know. (1) Newness. Air forks are not new to motocross. As far back as 37 years ago, Yamaha was offering YZ125, YZ250 and YZ400 models with air forks, the so-called “speedo and tach” forks. The idea had merit, but was hampered by incredibly bad damping and the tendency of the air to expand with heat, which made the forks get stiffer as the race wore on. ( 2) Nitrogen. Although virtually every local racer will use air in the PSF forks, the factory teams will run nitrogen. ( 3) Base setting. The base air-pressure setting is 35 psi, but that is only the pressure at the start of the moto. Depending on the length of the moto and the roughness of the track, the PSF forks can gain as much as 5 psi due to heat expansion. ( 4) Never-exceed number. The suggested pressure range on the KX450F is 32 psi to 41 psi. Never pressurize a PSF fork leg to more than 73 psi. ( 5) Balloon. Air works as a spring when it is compressed (think of what happens when you squeeze a balloon). An air spring ramps up as it travels through its stroke. It can be easily adjusted to stop bottoming. Changing a steel coil spring is a labor-intensive job; adjusting air pressure only takes a few minutes. ( 6) Extra cash. Budget an additional $49.95 into the price of the KX450F, because you must buy a KMC or DRC suspension pump to put air in or bleed it out. The bike comes with the special Schrader adapter valve required to access the PSF air valves (which are not Schrader).
Less is more: Last year the KX450F was a
fire-breathing dragon. Fast riders loved its
instantaneous response. But, there was a
more vocal group who felt that the power was
too pro-oriented. The result? The 2013 KX450F
engine is a kinder, gentler giant.