This fall, the 2010 YZ450F received the lion’s share of updates and media hype due to its fuel injection system and reversed cylinder. Those sweeping changes on the big bike forced the carbureted 250 back into the shadows, but they shouldn¹t have. The YZ250F saw big changes of it’s own for 2010, without taking away from the vital ingredients that have made it such a success for Yamaha.
Lets start with the new bilateral aluminum frame, constructed from a combination of forged, extruded and sheet aluminum welded to form a single unit. This makes the new bike more compact than previous models, more rigid and much easier to access the top-end of the engine for service with the engine in the frame. The wheelbase, rake and trail were massaged to enhance steering and stability; the damping and rigidity characteristics of the KYB fork were also updated and the rear shock spring now sits lower to accommodate a new airbox.
This new frame is dressed with slimmer, more aggressively European style plastic that ages better than years past and is also available in white. This new chassis has slimmer, trimmer ergonomics than ever before. There are adjustable handlebar perches on the new triple clamps, and the new fuel tank carries gas lower and further back than in 2009. Yamaha claims a wet weight of just 224.4 pounds for the new machine.
You might think the five-valve engine is unchanged, but you’d be wrong. The cylinder head features a new ‘D’ shaped exhaust port to increase exhaust gas velocity, plus lighter weight aluminum valve retainers and new softer-rate valve springs. The transmission ratios in third and fourth have also been changed to better suit the new engine’s powerband. The clutch is now actuated by a revised push lever cam, which reduces clutch pull effort.
Feeding the new mill is a revised airbox, with a funnel shaped intake designed to improve low and mid-range power. That air gets a straight shot into the Keihin FCR-MX37 carb, which has been updated with a new accelerator pump cam and a reshaped carb throat. Keeping the engine cool are bigger and stronger radiators than last year’s model. Spent gases get shot from a new exhaust system that uses a 50mm longer muffler to reduce noise without hurting performance.
Enough already, what’s it like to ride this sucker? The new engine barks hard off the bottom, with enough torque to make one of our intermediate-level testers remark, “Are you sure this is a 250F?” From mid-range and up the power builds strongly and controllably, right up until it hits the rev-limiter. Clutch and shifting action are flawless as well, but with so much bottom end you don’t need to shift as often or resort to clutch abuse as you do on other 250Fs.
That great powerband should work wonderfully off the track as well, and it does…to a point. It’s here where the carburetor-blues haunt the bike. In low-rpm technical off-road situations the YZ250F still exhibits the old four-stroke "cough and die" syndrome that drives woods racers mental. When it happens it takes several healthy kicks and use of the hot-start button to relight. On a motocross track you’ll never notice this tendency, but off-road you never get over the feeling that the carb could flame out when the going gets tight. That’s a shame, because that snappy low-end biased powerband makes hopping over logs and rocks a breeze.
Cornering with the new chassis and suspension is great, though the Bridgestone tires weren’t well suited to our wet track conditions. Stability at speed is very impressive, without a surprise wiggle or squirm at high speeds over nasty whoops. No doubt the great suspension and ergonomics contribute to the bike’s prowess in that department.
The bike feels light, slim and aggressive to ride. Coupled with its aggressive powerband, the YZ250F inspires riders to go faster. That light feel helps it work in the woods as well, and backing off the compression on the fork seven or eight clicks lets it work acceptably off-road for all of you one-bike-does-it-all riders. There’s even a sturdy plastic skid plate to protect the oil tank and lower frame rails! The final drive gearing is too tall for tight woods work, so we’d recommend adding a couple of teeth to the rear sprocket if you are racing off-road. The new, bigger radiators help cooling as well. Our test YZ-F never steamed no matter how much we abused the clutch on hilly singletrack trails or on the muddy motocross track.
So what do we think? The most recent bike we can compare the YZ250F to is the 2010 Honda CRF250R. The CRF had a more refined feel to it, started easily and never misbehaved even when we chugged around on it like a trials bike. The YZ250F has more power everywhere than the Honda, better clutch feel and more aggressive suspension settings. As such, we’d say the YZ250F is a superior motocross-only weapon than the Honda, but it never lets you forget you’re on a race bike if you take it off the track. The Honda is a great motocross bike that is equally happy pretending to be a docile playbike when you aren’t racing.
Other stuff? The Yamaha looked fresher and sounded tighter at the end of the test than the Honda did after a similar amount of riding time, so kudos to Yamaha for their build quality and improved plastic. The Yamaha also looks more modern and by virtue of its long history has huge aftermarket support for the engine. Support for the new Honda will catch up, but at this point the reliability of the all new CRF250R engine and EFI system is unproven.
So, how does the new YZ-F really stack up? You have to decide if you want to race motocross only or will be mixing it up with some off-road racing. These days, with such huge growth in GNCC, WORCS, Enduro and Endurocross racing, a motocross bike has to be able do everything to be a runaway sales success. The Yamaha YZ250F will do whatever you ask of it, but where it really shines is on the motocross track.