We spent a day shredding Piru Motocross Park on Yamaha's new quarter-liter offering. The track is suited to 250Fs and we weren't disappointed in the least.
The changes are few and far between for the 2008 YZ250F, but what changes have been done are smooth moves in refining an already stellar package. Every year we test the little YZ-F in our 250F MX Shootout, and every year our testers form a love/hate relationship with the Yammie. The highest praise and loudest complaint is always that the YZ-F does everything exceptionally well, but nothing about the bike stands out as a signature feature. The new model is in exactly the same position and with solid performance on all fronts; it's a good problem to have.
The only real news in the motor department is a boosted compression ratio. Thanks to a redesigned piston, the YZ-F now boasts a 13.5:1 ratio compared to the 2007's 12.5:1. Walking into Piru Motocross Park for our first introduction, we were expecting gains in the bottom and mid-range of the 5-valve, DOHC motor. Sure enough, both of our testers felt some extra grunt as we blasted berm to berm, uphill and down. Admittedly, the Piru course is well-suited to the output and handling of a 250F. But the Yamaha's added performance will help riders on any track. Our faster rider also happens to be lighter. Weighing in at a buck-fifty, Alvin Zalamea closer resembles the targeted riders than our 5'11"-tall, 185-pound secondary rider.
"The bumped-up compression made a huge difference and you can feel the deep, throaty bark that the motor offers," Zalamea says. "It has a lot of low-end torque."
Short shifting the motor is more effective on the 2008 model which suited our larger rider's personal tastes. But, the YZ-F is still capable of being ridden like a 125cc 2-stroke. Revving the piss out of it is equally as effective, and particularly suited our smaller tester.
"I'm so glad these bikes have more over rev because I tend to stay up in the higher rpm, even when I'm not supposed to," admits Zalamea. "At the end of the day I was using the motor all over the track in second, third and fourth gears. For a first impression the '08 motor felt really good. It really amazes me how far these bikes have improved."
One of the things we were concerned with was that the extra compression might give the YZ-F a bad attitude towards starting. We were happy to find that the 250F is no harder to start than before and usually lit within a few kicks, even when hot.
The Kayaba fork is great at handling the lighter, smaller rider. Once the rider's size and speed start to increase, the KYB front could stand to be a little stiffer even though it has revised internals this year.
Last year saw the engineers focus much of their attention on lightening the front end for improved handling. The bike certainly turned well then and is still as sharp, if not sharper. Deciding how to get the bike to turn was the largest discrepancy between our testers' notepads. However, the way it was sorted out had more to do with the suspension than the chassis. As far as the aluminum frame is concerned, the Yamaha is very well balanced. If anything it's a bit harsh at times when faced with multiple sharp impacts or large jump landings, but aside from some extreme ends of the spectrum, the cast, forged and extruded chassis is forgiving.
"The bike tracked straight through Piru's uphill rhythm section, one of the most jarring sections of the track. I went in sideways one time and the bike seemed to pull itself into shape. The frame didn't feel too rigid or twitchy; in fact it felt just right. The best thing is that there was nothing unexpected from the chassis and the response was very predictable. I did, however, have a bit of problem finding places to grip the bike as I am used to the perimeter style frames on the other Japanese bikes."
The only complaints lodged about the 48mm Kayaba fork emerged in situations where there wasn't a lot of weight on the front wheel. One particular uphill sweeper was filled with nasty acceleration bumps and the front suspension would sort of wash over the top of them. A little sketchiness there and an avulsion to square-edged holes on a similar grade were the extent of our concerns. For the other 99% of the track, the fork was excellent. It would bottom once or twice per lap on some of the larger flat landings so faster/larger guys may need stiffer springs.
"It felt supple over the small chop and handles the hard hits really well," sums Zalamea. "I purposely cased some double jumps and flat-landed a few singles just to see how well the suspension would respond. Needless to say, I was very impressed at how well the bike handled the abuse considering it is completely stock."
Maneuverability is at a premium on the 250F. Our tester's short stature fit right into the cockpit without any problems.
The statements were mirrored for the KYB shock, which gets a revised linkage ratio. The combo settles well into turns but doesn't pack down on acceleration bumps. We also had excellent results in controlled rebound damping where a chopped throttle, mistimed jump or tricky kickers could have sent us into a flying W, but instead the YZ-F absorbed it all in with relative grace.
"I adjusted the sag from 100mm to 105mm and that seemed to suit my riding style a little better," explains Zalamea. "There was one particular section of track with two big braking bumps, and I hit them square every lap in either fourth or third gear. The bike soaked the bumps right up without bucking me over the bars. I'm really impressed with how balanced the suspension package is in '08."
Getting on the Yammie and moving around is one area where a rider might find something to nit pick. We know some tall, skinny 250F riders who might find themselves hunched over on the YZ-F, but smaller guys like Zalamea will have no problems at all. Alvin raved about the ergonomic fit, but our larger rider felt that a taller handlebar would benefit the blue Thumper.
"The ergonomics felt perfect for my body build and riding style," gushes the 5'8" Zalamea. "The new peg position makes the bike feel roomier than last year, and the new width is a huge ankle saver on those flat landings and cased jumps. I can always feel exactly where my feet are and re-position my feet as I'm going into corners or getting ready to soak up a big landing. Stock bar position and levers are perfect and it's so slim and slender that it feels like a 250cc 2-stroke under my legs."
Good suspension and brakes make it possible for hard acceleration at the start of downhill sections. Both components live up to Yamaha's reputation of high marks across the board.
Those levers Alvin was mentioning are connected to exceptional components. The clutch is a breeze to operate and the transmission is forgettable in the best sense of the word. You don't have to think about shifting any more than the bare minimum. There were a few missed shifts, but both testers attributed it to rider error more than mechanical flaw.
"The gear ratios felt really good," notes our pro tester. "A short shift from second to third and the motor just pulls. I did find the transmission a bit notchy to downshift in some areas of the track."
And the brakes, oh yes, the brakes. Both front and rear provide great feedback to the rider. If we had to pick which was better, the dual-piston, 250mm wave rotor front would get the nod. The single-piston, 245mm rotor combo out back is great as well, but the forward pinchers really grabbed our attention. Apparently Yamaha is satisfied with them as well since it installed the 250F unit on every full-size motocross bike they manufacture.
"It got to where I seemed to only use the front brake at Piru, but I know I was using both brakes," says Zalamea. "The front just worked really well. It wasn't too much but just right in the corners and I could use it to drop the front end and grab in rough, rutted corners."
Typically, as the day wears on and the track develops hard-packed grooves in the main lines, testers often find themselves easing the pressure on the front brake and relying more on engine braking and the rear binder. A self-preserving fear of losing the front end under hard braking is the culprit, but we were surprised to find ourselves consciously applying more bite to the front at Piru. The track certainly had its hard-packed lines, especially on the downhill and through the sweepers, but the front brake is so easy to modulate that we were able to overcome the natural tendency to compensate with the rear.
New Bridgestones are equally as good at providing traction while accelerating or braking. The new meats are just the icing on the cake for Yamaha's lightly revised YZ250F.
Part of why the brakes are so impressive is the fact that Yamaha switched to a new set of Bridgestone tires for 2008. The 403/404 front/rear combo is a much better set-up than the Dunlops of years past. It was the first time we've ridden these meats and both of our testers came back to the truck with nothing but positive feedback. The track was heavily watered in the morning, dried out to a perfect loam by noon and then baked to a hard crust in the afternoon. The spread of terrain conditions was perfect for testing an intermediate tire, and the Bridgestones performed admirably. The best results were churned up in the loam and hard-pack, but we don't think we'd have to buy a new set of tires right away. In fact, we'd consider purchasing the same model when it comes time because they mate so perfectly with the Yammie.
With small changes sprinkled across the bike, from the hand controls right down to the tires, Yamaha has definitely improved the YZ250F. As popular as the quarter-liter machines are, there's no doubt that Yamaha needs to stay on top of the game in order to remain competitive. Like we've mentioned, the YZ-F does everything so well that it almost hides how great of a ride it is with an incredibly smooth vanilla flavor. But that's just it, everybody likes vanilla, and since that's the case, enjoying the 2008 YZ250F is easier than ever.
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