Yamaha 250F & 450F bike test

Published: 18th January 2008

Author: Words by Chris Hammal Photos by still-mx.co.uk

Yamaha have ruled the GP scene over the last couple of seasons with their brace of flying thumpers so we couldn’t wait to get to grips with a ’08 limited edition white 250F and a more conventionally-coloured blue four-fiddy…

Yamaha have dominated world motocross in the last couple of years with Stefan Everts, Josh Coppins, Tony Cairoli, Billy MacKenzie, Davide Guarneri and Nico Aubin all taking the striking blue bikes to overall GP wins. In fact during the two seasons since Yamaha introduced the latest ally-framed incarnations of their very successful YZF range, the Yamahaulers have crossed the line first in 63 per cent of MX2 GP motos and 65 per cent of MX1 scraps at world championship level – that’s pretty darn dominant!

It’s 10 years since Yamaha released the first of the new-generation of short-stroke four-poppers to the public, the first being a 400cc model which later became a 426 then 450cc bike in 2003. Two years before Yamaha settled on a 0.45 litre capacity for their Open class weapon the YZ250F was launched and that soon became a must-have weapon for pro-class privateers in what was then known as the 125 class.

When you consider it took until 2002 for Honda to chuck out a rival 450 – and Suzuki and Kawasaki entered the Open class four-stroke wars even later than that – and 2004 before any rival manufacturers’ 250Fs were let loose you wouldn’t be crazy to think that Yamaha would be way ahead of the game in terms of reliability and performance. Unfortunately for Yamaha and despite what the GP results might tell us that’s not actually always been the case.

Catastrophic valve failure haunted more than a few owners of zero-six 250Fs – the first of the ally-framed four-stroke models – but luckily that problem was quickly solved. Since then not much has changed – visibly at least – and the bikes look much the same for 2008 as they did for ’06 except for matt black engine cases which look great probably until you ride it. Other visible changes include sleeker looking fork guards and new graphics but the more important changes can’t be seen by the naked eye.

The 450 might be missing the stamped service-free silencer spotted on the American models – this is probably because of the tighter noise regulations the European market has – but there are plenty of engine, chassis and suspension mods to keep the blue – or white if you wanna spend an extra 50 bones to get something a little different – MX1 missile at the front of the pack.

The motor has reshaped intake ports to enhance the bike’s low to mid-range performance. To compliment the porting work new cam profiles change the valve timing helping create a better balance of both intake and exhaust performance for increased combustion efficiency. Tolerances throughout the engine have also been reduced which must make them tighter than a duck’s ass in water.
          The Yamaha engineers have reduced the backlash between the primary gears and also within the balancer gear making for better meshing which also ensures even lower levels of mechanical noise.

The chassis has a new steering head tube which is 5mm shorter, as is the steering stem inside. The forged aluminum lower triple clamp is all new, featuring a ‘H’ shaped cross section which makes it stronger and lighter than before. Staying at the front end the forks have newly designed outer tubes with a more compact oil seal housing design which helps to reduce overall weight for lighter steering characteristics. Clicker settings are also revised.

The rear suspension has been changed to compliment the front and there’s a new specification titanium spring – the collar and shaft are redesigned and the linkage ratio has been modified.

On the controls the front brake has a new lightweight assembly – the same fitted to the 250F last year – and features a new caliper with smaller pistons and smaller pads. The master cylinder has been reduced in size to save weight and the lever has a new design – so it’s no good keeping that spare in your tool box anymore.

The nerds at Yamaha have shaved more weight by using a lighter axle, collar and wavy discs with elongated slots rather than circular holes. To keep your feet planted there’s also new 55mm stainless steel footrests.

Now if you’re still with me I’ll move onto the 250. Yamaha must be doing something right as we all know how dominant Tony Cairoli is on his Yamahauler. The one we tested was a limited edition white one which looks very nice.

The engine has had a few tweaks for 2008 with a new lightweight high-compression piston raising the compression ratio from 12.5:1 to 13.5:1. To help handle this higher ratio the clutch assembly has been redesigned to increase oil flow to the plates. The transmission backlash between the primary drive and driven gear has been reduced and the 250F has a new quieter silencer – 94db – as well as fine tuning of the carburetor and CDI. The 250F also features a new shape rear brake pedal which is lighter too and the chassis has all the same changes as the 450F – don’t worry I wont bore you with that all again.

I was interested to see how the 2008 YZFs would perform on the Tonymoto track. It’s 11 years since I watched in awe as Doug Henry won the last supercross of the ’97 season by a long, long way on a factory YZF400 – I don’t think anybody back then had even the slightest inkling of the impact the new generation of four-strokes would make on our sport over the next decade. Yamaha were of course the first Japanese manufacturer out of the gate with their 400 (later to become the 426 then 450 model) and so I was keen to see how it would perform on a freezing cold winter morning in Winchester – you can’t get much less Vegas than that!

Until this day DBR had not tested an ally-framed YZF450. Certain staff members have ridden and even raced them but Yamaha have never ponied up a bike for our test team to dissect – fools! Out on the track this bike has plenty of pull and torque but not in a negative way. It’s all useable power and even from a slow speed you can just snap the throttle on and it will grunt away with so much power and traction I even found myself coming out of one corner rodeo style as my left hand slipped from the bars due to the unexpected delivery of power and grip.

For a big four-stroke the 450 handles great – more like a 250F only with loads more power. It’s a very well-balanced bike and you can throw it about and it doesn’t feel heavy or hard work and doesn’t fight back. I like the bigger, higher footrests which allow me to move about on the bike easier but on the other hand I didn’t like the high seat height – in the corners I felt more perched on top of the bike rather than in it.

The steering is good. In the corners it is very responsive and gave good feedback and I didn’t have any unwanted surprises. I couldn’t test the suspension very well as the two tracks at Tonymoto were groomed to perfection and smoother than a Barry White album. I landed hard a few times and it soaked it all up well with a plush feel.

Overall I’d say this is a great bike and would be very competitive in almost anyone's hands. I had a lot of fun on it and I didn’t want to take it back.

The YZ250F is a bike I know quite well – I raced one full time in ’06 – and so I was equally eager to take this for a spin to see how much Yamaha had improved the bike since then. Out on the track it felt like a good all-round bike. The power isn’t massive but the delivery is nice and smooth and revs out well making it very rideable.

The handling felt a lot like the 450F – damn good in the corners and easy to control everywhere else. I think the suspension is set up for those fat burger-eating Americans because it is hard from new but that's a thing that you can of course adjust to suit you.

Specifications YZ250F

Capacity: 250cc

Bore and stroke: 77.0 x 53.6mm

Transmission: Five-speed

Carburetor: Keihin FCR MX-37/1

Front suspension: Kayaba fork (300mm travel)

Rear suspension: Kayaba (307mm travel)

Front brake: 250mm disc

Rear brake: 245mm disc

Wheelbase: 1469mm

Seat height: 997mm

Dry weight: 92.7kg

YZ450F

Capacity: 449cc

Bore and stroke: 95.0 x 63.4mm

Transmission: Five-speed

Carburetor: Keihin FCR MX-39/1

Front suspension: Kayaba fork (300mm travel)

Rear suspension: Kayaba (307mm travel)

Front brake: 250mm disc

Rear brake: 245mm disc

Wheelbase: 1495mm

Seat height: 1001mm

Dry weight: 99.5 kg