WITH a new, alloy, frame and totally new motor, Yamaha’s YZ450F has been built to maintain the bike’s reputation as the machine to beat in the premier four-stroke motocross class. Yamaha has taken the performance of the YZ450F to another level with the 2006 model, leaving most other manufacturers playing catch-up, again – and some of the credit is said to be due to Chad Reed, who has been riding the machine for some years now.
Almost totally redesigned from the ground up, much was expected from the 2006 model, and from our two-day introduction to the machine at the Australian launch, it delivers. For 2006 the bike will be available in the traditional blue, but there’s also going to be a limited number available in Yamaha’s 50th Anniversary colours of yellow, black and white, but if you want one of the retro-styled machines you’ll need to be quick. No pricing has been announced yet, but we do know they should be in dealers at the end of November.
The new motor is very different in the way it delivers the power. It hooks up when previous YZ’s would spin up, which makes the newest 450 easier to ride and a faster machine. The fire breathing machine’s heart is a redesigned titanium-valved DOHC 449cc single. There’s a new piston, crankshaft and connecting rod for increased performance and durability. The cylinder head angle has been changed, the dry sump oil tank moved in the crankcase to improve overall handling and to remove the external oil lines. A new internal oil jet directs engine oil at the piston underside for increased cooling.
Feeding the beast is a 39mm Keihin carburetor with TPS (throttle position sensor) and redesigned titanium header pipe (with a power chamber to smooth out the delivery) and muffler are matched perfectly to deliver lightning-like throttle response and a exhaust note that sounds like deep thunder but not too loud. The radiators have a larger core but are narrower to keep overall width to a minimum. Even the kick starter is new and provides easier starting than ever before.
The gearbox gets a fifth cog back – missing for a couple of years, I reckon it’s a good thing for motocross, but it’s almost essential for other forms of racing that include supermoto, dirt track and desert racing. The changes made to the engine are not so drastic to sacrifice the reliability Yamaha has proven since way back in ’98. Yamaha has built a really strong engine with heaps of torque. It is capable of getting good starts in any race you enter and for a 75kg rider like myself I had to ride a gear higher everywhere using the torque off the bottom and mid range to find traction on hard pack and slippery surfaces, but in the loamy dirt it explodes the soft berms like they are packed with TNT.
The new motor is also very smooth, new internal balancer weights damping the vibration levels right down. Despite the high 12.3:1 compression ratio, premium unleaded fuel worked fine without any major adjustments to the jetting and air screw. Even the dip stick is remounted on the case in front of the cylinder instead of on the side of the frame. The clutch feels lighter than the previous model, and the stock final gearing (13/49) should be good for the average Australian motocross track – but it’s a shame the chain isn’t a decent quality O-ring type, you’ll be replacing the stock item pretty quickly.
Yamaha has taken longer than most to change to an aluminium chassis, claiming to spend the time developing the suspension to suit the stiffer alloy before releasing it to the public. The all new frame itself is made up of cast, forged, pipe and extruded aluminum (which is both lighter and stiffer than steel, the main reasons for the change) to get the strength and flex where they wanted it.
The seven litre fuel tank sits lower in the frame for lower centre of gravity, and another great change (and it’s about time) is the top triple clamp with removable bar mounts and Pro Taper handlebars. What this means is that you don’t have to buy new handlebars and triple clamp like on previous year model bikes that come out with crap steel handle bars (2005 had alloy bars but no adjustable/removable bar mounts) that would bend easily.
The 450 feels very balanced – while testing on a motocross track I could steer the bike anywhere and change direction at any time through the corner. No doubt the low weight of the bike – Yamaha claims 99.8kg (dry) for the machine helps here. The suspension is awesome out of the box, the 48mm Kayaba forks feel really plush across braking and acceleration bumps even on the stock clicker settings. On a track with bigger jumps or G-outs I would have to move the compression in a few clicks. The rear Kayaba shock is fitted with a 5.4 kg titanium spring to further reduce weight by 500g and the shock rod is 2mm larger taking the diameter to 18mm to improve strength. A new hi-tech Kashima coating reduces friction for more response and feel. The new swingarm design helps lateral rigidity with a different linkage ratio. The gripper seat is needed to keep you from sliding back under the hard acceleration.
The 2006 YZ450F is not only more powerful and lighter than earlier models, it’s also a lot easier to ride fast, which means you can ride harder for longer before fatigue or the dreaded arm pump kicks in. The new chassis makes the bike a lot easier to throw around. The adjustable perches on the new top triple clamp are a welcome addition and are the final touch to making the bike race-ready out of the box. If you’ve got the ability to ride one of these things fast, it’ll put a smile on your face a mile wide. We can’t judge value for money yet because pricing hasn’t been announced, but it’s sure to be competitive. The bike itself is an awesome piece of kit which will continue to see lots and lots of blue (and now Yamaha yellow) at races around the world.
2006 YZ250F Yamaha took the top three places in this years world motocross MX2 class with the YZ250F, including one ridden by Aussie Andrew McFarlane into second overall. With a racing pedigree like that it’s no wonder the YZ250F is so good and so popular – and for 2006 it’s even better. Like its big brother the 2006 Yamaha YZ250F gets all the new bits including the new generation alloy frame, new Kashima coated 48mm Kayaba fork and Kayaba shock (with titanium spring and 18mm shaft), adjustable triple clamps and protaper handle bars, and all new plastics.
The 249cc engine only receives minimal changes like the oil sight glass on the side of the case for easy oil checking, a new exhaust system, new CDI ignition unit, larger radiators and remounted dry sump tank to improve handling and balance. To look at it’s very impressive and to ride it is even more impressive. It is sensitive to suspension set-up, for I found it was running wide until I had a chance to tweak the clickers, but after that it was great. The engine feels a little stronger down low than the 2005 model, and the weight – just 93.5kg (dry) – makes it very easy to throw around. The 2006 YZ250F is due in shops soon – no price is available as Cycle Torque goes to press.
Daniel McKenzie is a rider trainer with the Academy of Off-Road riding. He is filling in for Miles Davis, who has an injured knee.