DMX Test: 2010 YZ250F

I read somewhere that Yamaha has sold something like 60,000 YZ250F motocross bikes since 2001. Yes, a “HOLY CRAP!” is in order. 60,000 units, in motocross terms, is freakin’ gigantic. The five-valve thumper redefined the small-bore class, made 125’s obsolete overnight and its torquey, easy to ride nature made amateurs feel like Pros.

As you know, the 2010 YZ450F has been getting all the media hype this fall due to its fuel injection system and reversed cylinder. And don’t worry; we’ve been flogging a 450 for you as well as its little bro. The sweeping changes on the big bike may have forced the carbureted 250 into the shadows, but it shouldn’t have. The YZ250F saw big changes of it’s own for 2010, without jeopardizing Yamaha’s successful recipe.

The 250F has a new bilateral aluminum frame, which is made from a whole pile 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 have all been massaged to enhance steering and stability, the damping and rigidity characteristics of the KYB forks have been updated and the rear shock spring now sits lower to accommodate a new airbox.

This new chassis has slimmer, trimmer ergonomics than ever before and can be ordered in white if you prefer the virgin look. Just be warned, a white YZ250F, like any new bride, starts looking old real fast.

Don’t be fooled into thinking the five-valve engine is unchanged. The cylinder head now has a new ‘D’ shaped exhaust port, lighter weight valve retainers and softer 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.

The new YZ-F breathes through a new airbox, with a funnel shaped intake designed to improve low and mid-range power. The Keihin FCR-MX37 carb has been updated with a new accelerator pump cam and a reshaped throat. The radiators are bigger and stronger than last year’s model, and exhaust gases burble from a new exhaust system with a 50mm longer muffler to reduce flatulence without constipating performance.

So, how’s it go? The new engine barks hard off the bottom, with enough torque to make one of our testers wonder if our test bike had a cheater motor. From mid-range up the power builds strongly and controllably 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 too much or abuse the clutch like on some other 250Fs. That great powerband should work wonderfully in the woods too, and it does…to a point. It’s here where the old-school carburetor-blues haunt the bike. In low-rpm technical off-road situations the YZ250F still does the four-stroke ‘cough and die’ spasm that drives woods racers mental. When it pukes it takes several healthy kicks, loud swear words and use of the hot-start button and to get it going again. On a motocross track you’ll probably never notice this tendency, but off-road you never get over the fear that the bike will gag when the going gets tight. That’s a real shame, because that snappy low-end biased powerband makes hopping over logs and trail junk a breeze.

Cornering with the new chassis and suspension is great, though the Bridgestone tires weren’t well suited to our wet test conditions. Stability at speed is very impressive, without a surprise wiggle or squirm at high speeds over nasty whoops. 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 handle in the woods too. We backed off the compression on the forks seven clicks in the forest and were happy leaving the shock alone. 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 going hare scramble racing. The new, bigger radiators are awesome; our YZ-F never steamed, no matter how much we abused the clutch on hilly singletrack trails or on a very muddy motocross track.

So what do we think? Compared to the 2010 Honda CRF250R, the CRF had a more refined feel to it than the YZ-F, started easier 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. 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. Since it’s been around forever, the Yamaha engine also has huge aftermarket support. 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 mix 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 do everything pretty damn well to be a runaway sales success. The 2010 Yamaha YZ250F can be forced to race anywhere, but where it shines is on the motocross track.

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