Using the most advanced race-bred technology developed from
Grand Prix winning MX1 and MX2 race programmes, Yamaha's engineers
have further refined the winning YZ250F for the new season.
The newly released 2007 model is available in two guises -
Yamaha Blue/White and Special Edition White/Silver - and features a
number of significant improvements aimed at further boosting engine
performance and delivering even lighter handling qualities.
Nothing comes close to matching the YZF's track record, and the
new features and advanced technology introduced for 2007 are aimed
at reinforcing and extending Yamaha's position as the leading
manufacturer of race-winning motocross machinery.
The YZ250F made an indelible mark on the competition when it
totally dominated the 2005 MX2 World Championship, taking the first
three places overall (and five out of the top seven), earning
Yamaha the 2005 MX2 Manufacturers' Championship.
With its combination of a rider-friendly power delivery,
class-leading handling and lightweight steering, it is easy to see
why the YZ250F has become one of the dominant bikes in the MX2
category. And development continues for the 2007 model.
YZ250F ENGINE
Although the basic architecture of this MXGP-winning 5-valve
DOHC engine remains the same, a wide range of improvements to the
intake, exhaust and ignition systems ensures even greater
performance at high rpm and also in the over-rev range. These
changes include a redesigned diffuser pipe, modified carburettor
air vent passage, and new carburettor settings.
The YZ250F is already renowned for its lightweight handling
qualities, and to further enhance this reputation the 2007 model
benefits from a revised engine mounting angle. In effect the engine
has been rotated around the drive axis so that the cylinder is more
upright.
This change, together with the use of a range of new components
including a lightweight engine guard ensures even lighter feeling
handling. Further weight savings are achieved with the use of a new
magnesium crankcase cover which is 168g lighter than the previous
design.
The dry sump engine features a separate oil tank positioned in
front of the engine, and for 2007 a newly designed tank is fitted,
featuring an additional internal partition which improves the
oil/air separation. This has allowed our engineers to reduce the
engine oil volume by 100cc, thereby saving weight.
2007 YZ250F Engine Technical Highlights
· Liquid cooled 250cc 4-stroke
· DOHC, 5-valve
· Bore x stroke 77.0mm x 53.6mm
· Revised carburettor settings
· Optimised intake, exhaust and ignition settings
· Revised engine mounting angle
· Magnesium crankcase cover
· New oil tank with reduced volume
YZ250F CHASSIS
In order to accommodate the more upright engine angle, the
YZ250F's frame has been modified, and the head pipe is now slightly
closer to the rider. The frame's rigidity balance has also been
modified by the use of a smaller diameter engine mounting bolt,
while the engine mounting plates are also redesigned to allow for
the new engine mounting angle.
The effect of these changes is to give a slightly more compact
riding position, which makes for improved handling qualities,
particularly when entering turns.
Any weight reduction is significant, but weight saved at an
extremity of the machine - or from any part of the unsprung chassis
- reaps the greatest rewards in terms of enhanced handling
performance.
Featuring irregular shaped holes, the wave type discs not only
reduce weight, they also enhance braking performance, and can also
offer improved pad cleaning properties in muddy conditions. Further
weight savings are made with the use of a newly designed brake
hose.
Further weight reductions have been achieved by the use of a new
compact front brake caliper. By reducing the piston size and
redesigning the master cylinder and brake lever, we have been able
to reduce overall weight by 228g, while at the same time increasing
braking performance.
The 48mm Kayaba front forks have also shed some weight for 2007,
and now feature new outer tubes which are lighter, and offer a
revised rigidity balance for improved handling qualities. In
addition, the YZ250F also benefits from new front axle brackets.
The new axle brackets offer a better balance, and complement the
new front brake caliper to give progressive and controllable
braking performance.
Both the upper and lower triple clamps are new for 2007, and are
now manufactured from forged aluminium, compared to the cast design
used in 2006. Further weight savings are made by the fitment of
shorter fork clamp bolts in the upper and lower triple clamps, and
the handlebar mounts feature a smaller diameter M10 fastening bolt.
Not only do the
forged clamps and associated parts reduce overall weight, but their
revised rigidity also helps contribute to the feeling of lighter
steering that enhances overall ride quality.
New Pro Taper handlebars are used to achieve an improved riding
position and give an enhanced appearance. The bulged section also
features useful reference marks allowing the rider to experiment
with different bar positions.
The innovative rear shock with its titanium spring has been
lengthened by 1.5mm for 2007 to give a slightly higher ride height
to achieve an even lighter handling feeling, and the use of new
aluminium components in its construction reduces overall
weight.
Yet more weight has been shaved by lightening more than fifty
bolts, and the surface coating of many nuts and bolts is now
stainless for improved appearance.
2007 YZ450F Chassis Technical Highlights
· New lightweight forged aluminium triple clamps
· New wave type discs
· New lightweight rear shock
· Range of stainless and lightweight parts
· New Pro Taper handlebars
RRP for 2007 remains the same at $10,299 and the SE White Silver
model costs a fraction more at $10,399.
Sean Hawker, advertising and PR co-ordinator
Yamaha Motor Australia,
489-493 Victoria Street, Wetherill Park, NSW 2164
Office: (02) 9757 0068 Mob: 0438 423844 Fax: (02) 9757 1384
Website: www.yamaha-motor.com.au