MXA RACE TEST: The New 2009 YZ250F Four-stroke; Suspension Settings, Jetting Specs, Likes & Dislikes, Plus Much More

INSIDE THE MXA TEST OF THE 2009 YZ250F

In last year’s test of the 2008 Yamaha YZ250F, the MXA wrecking crew stated that we thought the YZ250F was getting outdated in comparison to its newer and more modern competition. We hoped, and half expected, that for 2009 Yamaha would come out with guns blazing and have an all-new YZ250F engine. Instead, Yamaha has made remedial changes to a bike that ruled the roost from its inception in 2001 through 2005.

Today, the YZ250F engine is getting long in the tooth, although the rest of the bike is still contemporary. While we yearn for something new from the blue crew, considering the tumultuous world economy, we understand that 2009 isn’t necessarily the most opportune time to invest millions into R&D. But we are also wise enough to know that the decision not to develop a new engine was most likely made three years ago?when times were golden. Yamaha is gambling that the up-to-date chassis and awesome SSS suspension are enough to sway buyers to a bike with a nine-year-old engine design. Did Yamaha make enough changes to the 2009 YZ250F to bring it back up to the head of the class? That is what the MXA wrecking crew set out to discover.

Q: HOW MANY CHANGES CAN BE FOUND ON THE 2009 YZ250F?

 A: Seventeen to be exact (13 in the chassis and four in the engine). The vast majority of Yamaha’s R&D money was spent on the rear of the 2009 YZ250F (swingarm, shock linkage and hub).

Q: WHAT ARE THE KEY CHANGES THAT YAMAHA MADE TO THE 2009 YZ250F?

ÿÿ A: Let us count the top nine changes.

ÿÿ (1) Top triple clamp. Yamaha held out forever in triple clamp research, but we must tip our caps to them for creating a top triple clamp that offers two different bar clamp positions and four riding positions (10mm back, standard, 10mm forward and 20mm forward). Off the showroom floor the 2009 YZ250F’s handlebars will be mounted in the rear holes in the standard position. Interestingly enough, in the rear-mounted position the handlebars are 5mm further back than they were in 2008. The ProTaper 5XC-LO handlebar comes stock (this exact bend is only available through Yamaha dealers). Taller riders should opt for higher bars, moved foward.

(2) Swingarm. The new YZ250F and YZ450F share the same hydroformed swingarm, which changes the rigidity balance and flex. It is 12 ounces lighter than last year’s swingarm.

(3) Rear hub. Another shared technology with the YZ450F is the new rear hub. It’s more compact, weighs nine ounces less than the 2008 hub, uses a 25mm diameter axle (compared to 22mm), and has three smaller wheel bearings (compared to two).

(4) Linkage. The shock linkage has been redesigned to conform to the new swingarm. The new low-rider link is 0.8mm longer than the previous center-mount version, while maintaining the same rising rate. The biggest change is in the rocker arm, which is 8mm longer.

(5) Exhaust system. The exhaust system has the same tuned length as last year, but the head pipe is 60mm longer and the muffler is 50mm shorter.

(6) Clutch. The new clutch uses eight rubber shock dampers instead of last year’s six coil spring dampers. The judder spring has also been eliminated, which means that all of the plates are identical (in years past a separate hardened clutch plate was needed).

(7) Clutch lever. For the first time since dinosaurs roamed the earth, Yamaha changed their clutch lever. It is now shorter, stronger and adjustable.

(8) Chain. Yamaha equipped the 2009 YZ250F with a D.I.D. gold anti-rust coated chain.

(9) Seat cover. Yamaha dropped the gripper seat cover in favor of a textured weave seat top. It not only improves grip, but is more stain-resistant.

Q: IS THE 2009 YZ250F FASTER THAN THE 2008 YZ250F?

A: Yes, but not resoundingly so. Since Yamaha started with the same basic engine layout that they have used for the better part of a decade, it’s reasonable to state that the 2009 engine isn’t much different from the 2008 engine, which isn’t a whole lot different from the 2007 engine and so on through time. Just like trying to teach an old dog new tricks, the YZ250F’s personality can’t change overnight with a handful of mods. Still, Yamaha tried to strengthen the YZ250F’s signature low-to-mid powerband with some changes.

Exhaust system: The new exhaust system is 60mm longer at the head pipe and 50mm shorter at the muffler. The most important change to the exhaust system is that it only has three steps in its two main sections. Previously the YZ250F had a four-step exhaust system with three main sections. It is easy to see that the overall volume has been increased for 2009. Larger volume equals improved bottom-end power and snappier throttle response. For those who have an aftermarket exhaust system from a 2008 YZ250F, you can sleep easier knowing that it will fit on the 2009 model.

Ignition mapping: Yamaha made the timing less advanced from 7000 to 9000 rpm (at the small throttle opening). This modification offers more acceleration and more hit directly off the bottom of the powerband. Yamaha’s two major mods did perk up the power from low-to-mid. Compared to the 2008 model it’s substantially better off the bottom-end and pulls harder into the middle. It still falls off once the power curve goes over the top. Power is maximized by shifting before the engine starts to hang on top.

Q: HOW IS THE GEARING ON THE 2009 YZ250F?

A: Last year Yamaha was the only manufacturer to hit the nail on the head in the gearing department. Every other 250F needed an extra tooth on the rear (some even needed two). For 2009 Yamaha stuck with their 13/49 gearing combination. Add an extra tooth to the rear only on arenacross-style tracks.

Q: WAS YAMAHA ABLE TO DROP THE OVERALL WEIGHT OF THE 2009 YZ250F?

A: Yes, but not in the way that you’re probably thinking. As it sat, the 2008 YZ250F was a relatively light machine. The 2009 YZ250F is even lighter, but it could have been even more feathery. The new swingarm, linkage and rear hub account for the majority of the 2-1/4 pound total weight loss, but those weight savings were subverted when Yamaha switched from last year’s titanium shock spring to a steel spring for 2009. The steel shock spring added back 1-1/2 pounds of what would have been a hard-fought 3-3/4 pound weight savings.

Q: IS WHERE YOU LOSE WEIGHT MORE IMPORTANT THAN HOW MUCH WEIGHT YOU LOSE?

A: Yamaha engineers deserve applause for focusing on reducing unsprung weight. Backyard engineering calculates that unsprung weight is roughly seven times more important than sprung weight. Since unsprung weight (weight below the suspension) has to be stopped, started and damped every time the suspension moves, the weight of the tires, wheels, swingarm, linkage, brake rotors, calipers and chain is critically important. The 2009 YZ250F is lighter in terms of unsprung weight as opposed to simply tipping the scales at a lower number. Kudos to Yamaha.

Q: WHY IS THE UPDATED SWINGARM SO IMPORTANT TO THE CHASSIS OF THE YZ250F?

A: Yamaha’s focus of the hydroformed swingarm wasn’t just centered around unsprung weight; they also tried to alter its “rigidity balance.” Flex is shorthand for “rigidity balance.” Yamaha engineers felt that they could improve the cornering characteristics and traction capabilities of the YZ250F by increasing vertical and twist flex (while reducing horizontal flex). As a result, the 2009 YZ250F is improved in the areas of traction and cornering. The swingarm change is most noticeable in rutted corners and berms, as steering is very precise.

Q: HOW IS THE JETTING?

A: It is a little off, but doesn’t require much more than a careful fuel screw adjustment. Here are MXA’s recommended jetting specs (stock specs are in parentheses):

Main: 178
Pilot: 42
Needle: NHKR
Clip position: Fourth from top
Fuel screw: 2-1/2 turns out (two out)
Leak jet: 70
Notes: For 2009 the jetting is richer at half throttle and leaner at quarter throttle. Yamaha switched to the NHKR needle from last year’s OBEPQ. The new needle is the equivalent to the 2008 model needle in the sixth position. Yamaha has a whole new series of needles to allow for greater adjustability.

Q: HOW GOOD ARE THE 2009 KAYABA SSS FORKS?

A: Beginning with the 2006 YZ250F, Yamaha pioneered the Kayaba SSS (Speed Sensitive System) components. The MXA wrecking crew fell in love with them. Even in the 2008 250F shootout, we proclaimed that “The YZ250F’s Kayaba SSS forks work extremely well?so well that they are the best of the class.”ÿÿÿÿÿÿ

Yamaha has stuck with Kayaba’s SSS forks for 2009, which was a very wise decision. The firm spring rates, coupled with softer damping specs, actually allow the forks to use their full stroke.

Q: WHAT WERE OUR BEST FORK SETTINGS?

A: For 2009 Yamaha added more mid-to-high speed compression damping in both the forks and shock, which improves performance by keeping the suspension higher in the stroke. The fork’s valve setting and shim stack were also changed. We tested with a wide range of skill levels and always found a clicker setting that worked for everyone. For hardcore racing, these are MXA’s recommended 2009 Yamaha YZ250F fork settings:

Spring rate: 0.45 kg/mm
Oil level: 521cc or 145mm oil height
Compression: Eight clicks out
Rebound: Nine clicks out
Fork leg height: 5mm up
Notes: Determining oil height is very difficult because the fork internals are upside down. Regardless, the stock oil quantity is a good starting point for any skill level. Also, the handling on the YZ250F is very sensitive to fork leg height. Moving the fork legs up further than 7mm will cause instability at high speed and oversteering.

Q: WHAT’S NEW WITH THE YZ250F’S REAR SUSPENSION?

A: The shock linkage on the 2009 YZ250F is completely different, yet it’s still the same. Yes, you read that right. The old linkage bolted through the center of the swingarm, which required more mass inside the swingarm to properly support it. Due to the new hydroformed swingarm, which now has two underslung tabs, the linkage had to be redesigned. However, the rising rate is still the same as last year.

Q: WHY DID YAMAHA REVERT BACK TO USING A STEEL SHOCK SPRING?

A: Price. At a $650 retail price, the stock titanium shock spring was not cheap to use as an OEM part. Yamaha switched back from a titanium shock spring after three seasons for several reasons, but price was the major factor. A steel spring was last used on the 2005 YZ250F, but the cost of a titanium spring has nearly doubled since then. The main difference between steel and titanium is that steel is heavier. The spring rate between the 2008 and 2009 YZ250F is exactly the same, although the coil length and wire size of the spring is different.

ÿÿ We strongly suggest that you swap out the steel spring for a titanium one if you have an older 2006 through 2008 YZ250F and are in the market for a 2009 model. Just remember to install the plastic clips on the end of the titanium coil to stop the spring from binding. You can buy a titanium spring for the 2009 YZ250F (part number 1C322212-A0), but at $650 we don’t think that it’s worth it. Still, not only is the titanium spring 1-1/2 pounds lighter than its steel counterpart, but more importantly it further reduces unsprung weight.

Q: WHAT WAS OUR BEST SHOCK SETTING?

A: Yamaha made only slight clicker adjustments for 2009, because the 2008 YZ250F shock was very good. Like last year, we decided to run the high speed compression 1/4 turn out. Here is what the MXA wrecking crew ran in its 2009 YZ250F (stock settings are in parentheses):

Spring rate: 5.3 kg/mm
Race sag: 100mm
Hi-compression: 1-3/4 turns out (1-1/2 stock)
Low-compression: Nine clicks out
Rebound: Eight clicks out
Notes: It takes an hour for the shock to break in. Also, we used the high-speed compression to fine-tune the bike’s handling. Turn it out to lower the rear of the bike for fast tracks and in to raise the rear for tight tracks.

Q: WHAT DID WE HATE?

A: The hate list:

(1) Graphics. Did Yamaha change the graphics on the 2009 YZ250F? We think so, but we’re not quite sure.

(2) Shock spring. Yamaha could have truly gone for the gusto and kept the titanium shock spring on the 2009 YZ250F, which would have yielded a greater reduction in weight (both sprung and unsprung). Instead they resorted back to steel in order to cut costs.

Q: WHAT DID WE LIKE?

A: The like list:
(1) Triple clamp. Not every rider has the same preference when it comes to handlebar position. Yamaha created a new top triple clamp to offer two mounting options and four riding positions. Very cool.

(2) Suspension. We absolutely love Kayaba’s SSS system, and for good reason. It’s plush, handles chop with ease, and the forks and shock work well together. If only this suspension came on every other 250F, the world would be a better place.

(3) Swingarm. In an effort to reduce unsprung weight, the new hydroformed swingarm not only achieves its goal, but it does so in a technologically advanced way.

(4) Clutch lever. Yamaha’s clutch lever was the least favorite of the big five manufacturers. No more! The new clutch lever has adjustable reach, is shorter and stronger, uses fewer parts, and the dreaded up and down wiggle of the lever is gone.

(5) Unsprung weight. Yamaha’s engineers understand the benefits of cutting down on unsprung weight. Dropping unsprung weight is more important to the performance of the machine that overall weight.

(6) Rear hub. We like the fact that it’s light, but it also spins more freely thanks to three small bearings instead of two large bearings.

(7) Brake hose clamp. Gone is the archaic steel hose clamp, which has been replaced with an aluminum clamp that’s also 32 grams lighter. That’s good for you, but bad for DR.D, which sold aftermarket aluminum hose clamps in droves last year.

(8) Clutch. Yamaha has improved reliability with their clutch by creating a new clutch basket assembly. In 2008 the YZ250F’s fiber clutch plates were changed so that they were all the same. For 2009 all of the steel plates have jumped on the bandwagon.

9) Tire combination. Yamaha worked with Bridgestone to spec a different version of the 403 front tire, called the 403A. It has a flatter knob shape and sharper edges, which adds up to a wider footprint. The 403A/404 combination is much better than the previous 403/404 combo. The 403A is only sold through Yamaha dealers.

Q: WHAT DO WE REALLY THINK?

A: By now we sound like a broken record, but if only Yamaha had updated their engine and improved top-end power, the 2009 YZ250F would be the complete package. As it sits now, it’s a good race bike with great suspension and chassis. Perhaps 2010 will be the year when Yamaha kicks out the jams and introduces a new powerplant. Until then we are content with everything but the overall power of the 2009 YZ250F.

Check out the 2009 250F Shootout

You might also like

Comments are closed.