2006 YAMAHA YZ250F TEST

 

As much as a giant, monolithic, multinational corporation can be, Yamaha is a rebel. As a rule of thumb, Yamaha always takes the road less traveled. Need proof? How about the first single-shock motocross bike (Monoshock)? First Brake Activated Suspension System (BASS)? First power valve-equipped exhaust port (YPVS)? First aluminum-framed works bike (YZM500)? Or, the granddaddy of all firsts, the first modern-era four-stroke motocross bikes?

 

While the rest of the manufacturers were busy perfecting their two-strokes, Yamaha shocked the world by releasing purpose-built four-stroke race bikes. Then, while everyone else was cloning Honda’s Delta box, twin-spar, aluminum frame, Yamaha created their totally unique plug-and-play alloy chassis. Yamaha, behind a corporate image of automobile engines, pianos, tennis rackets, amplifiers and generators, is really the anti-hero of motocross manufacturers. They don’t follow. They don’t even lead. Instead, they head off in a totally new direction.

 

Where are they headed in 2006? Who knows? But they will be doing it from the saddle of a new aluminum-framed YZ250F.

 

Q:IS THE 2006 YZ250F ALL-NEW?

 

A:No. The obvious pieces of newness are the aluminum frame and Kayaba SSS suspension components, but the heart-of-the-matter, the engine, is the same-old same-old.

 

Q:DID YAMAHA MAKE ANY CHANGES TO THE 2006 YZ250F ENGINE?

 

A:We asked this same question last year when we tested the steel-framed 2005 YZ250Fand came up with the same answer: no. The Yamaha YZ250F is living off its laurelswhich date back to 2001. We’re not saying that Yamaha hasn’t changed anything on the mill since 2001, but the list is minor. Last year, it was the air boot. This year, it is the CDI magneto.

 

Q:IS THE 2006 YZ250F FASTER THAN THE 2005 YZ250F?

 

A:Yes, but we’ll bet that you thought we were going to say no. Even though Yamaha didn’t change the engine components, they did design a new exhaust system. The 2006 unit incorporates the now-popular “Step System” to feed back pressure at prescribed stages. The YZ250F has four internal diameter changes. The pipe starts out relatively small, then jumps up in diameter midway down the head pipe. It gets bigger again at the S-bend and steps up one more time right before the muffler.

 

The step exhaust helps the 2006 YZ250F hit stronger down low, pull harder in the middle and rev out further on the top.

 

Q:HAS THE COMPETITION CAUGHT UP TO THE YZ250F POWERBAND?

 

A:Since its 2001 introduction, the YZ250F has been the best 250cc four-stroke on the track. Although there are better-selling 250Fs, none have been able to match Yamaha’s quick rev, metered power and rapid acceleration. But for 2006, Yamaha’s reign as the undisputed leader in the power department is under attack. Both the KTM 250SXF and Kawasaki KX250F have powerbands that are equal to, if not better than, what the YZ250F is putting out.

 

Q:HOW GOOD IS THE YZ250F ENGINE?

 

A:It’s great. Yes, we know that we said that the competition had caught up to the YZ250F, but that

doesn’t make the YZ250F a loser. It has a fight on its hands, but no other 250 four-stroke engine on the track can match the YZ250F’s willingness to rev through its powerband. It exercises its gears quicker than the red, green, yellow and orange bikes, which means that you can shift sooner and transfer energy into forward motion more rapidly.

 

In the past, the YZ250F engine was so much better than anything the competition offered that it seemed untouchable. Now it is touchablebut it’s still a great powerplant.

 

Q:DID WE HAVE TO CHANGE THE GEARING ON THE YZ250F?

 

A:Yes. With one more tooth on the rear sprocket, the YZ250F literally explodes out of corners and allows you to short-shift into third gear without fear of bogging.

 

Q:IS THE ALL-NEW ALUMINUM FRAME THE CAT’S MEOW?

 

A:It depends on how much you like to hear cats cry. Maybe it was just us, but we expected more. If we sound disappointed, that’s because we are. Don’t get us wrong, we didn’t love the top-heavy feel of the old-school steel frame, but our expectations were so high that the alloy version could never have lived up to them.

 

The 2006 aluminum frame is lighter, the mass is better centralized, the top-heaviness is gone and, if we were just comparing old to new, the new frame is better than the old one. But it had a narrower window of opportunity to get the balance right. We had to fiddle with the sag, high-speed compression, fork tube height and handlebar setup to get the balance to where both ends worked in unison. It wasn’t as

difficult to get the steel frame in the sweet spot.

 

Q:ARE THERE SHORT CUTS TO TUNING IN THE YZ250F CHASSIS?

 

A:You bet. Here is the MXA tuning chart:

(1) Handlebars. The stock handlebars are too low. By our calculations they are 10mm lower than they should be. We hate to say this, but before you even ride the bike, switch out the stock bars for a taller bar bend or 10mm-taller bar mounts. We can’t stress how important this change is. We spent several test sessions trying to get rid of the low front end feel with fork and shock changes before we realized the bars were the culprit.

(2) Race sag. Set the race sag at 97mm. We know that the recent trend has been to run about 105mm of sag, but with the YZ250F’s new aluminum frame and swingarm, the more the rear end hung down, the less stable the bike was at speed. With the sag at 97mm, the YZ250F was stable at speed (although it still had a quirk or two).

 

Q:HOW GOOD IS THE 2006 YZ250F SUSPENSION?

 

A: Really good. For 2006, Yamaha tossed last year’s Kayaba AOSS (Air Oil Separate Suspension) in favor of the SSS (Speed Sensitive System) system. The rear shock was also the beneficiary of some serious Yamaha love.

 

Forks: Before we changed the handlebars, we tried turning in the Kayaba’s compression to get the forks to ride higher in the stroke. When that didn’t work, we sped up the rebound. That was a failure also, so we dropped the forks down till they were flush with the top of the triple clamps. It didn’t take us long to get the YZ250F all discombobulated. Amazingly, through all of our gyrations, the SSS forks worked like champs. After getting the handlebars we needed, we returned to the box stock settings and just added or subtracted compression damping for track conditions. Good stuff.

 

Shock: This is a works shock. It might as well have been stolen from Chad Reed’s bike. It has three works parts that few other showroom-stock shocks offer:    

(1) The 2006 shock has an 18mm shock shaft. It is 2mm larger than last year’s shock shaft. The larger shock shaft displaces more oil, which means that more oil is pushed through the valving sooner, which results in a more sensitive feel on small chop.

(2) All the internal parts of the YZ250F’s Kayaba shock are Kashima-coated to reduce friction. In addition, the shock reservoir has been increased in volume with a 30 percent larger reservoir to help control the heat and to compensate for the shock shaft’s increased displacement.

(3) The shock spring is made from titanium, but not just any titanium. This isn’t porous Russian Ti or low-dollar Chinese metal; it is high-quality, aircraft-grade, American-made titanium wire that is shipped to Japan for coiling.

 

All of these changes produce a shock that is more responsive to low-speed oscillations and ready, willing and able to take on big hits. It is very important to run your sag at 97mm. The bike is more stable at that setting. If you want to have the rear end hang down a little lower, you can achieve that by turning the high-speed compression dial out a quarter of a turn. As for the compression and rebound, we left them alone.

 

Q:WHAT DID WE HATE?

 

A: The hate list:

(1) The bars: We actually loved the oversized Pro Taper Contour aluminum bars, but hated how low they were.

(2) Handling: Yamahas have always been middle-of-the-road handlers. They have rarely taken chances, preferring to be stable and consistent rather than agile and quick. We wish they would kick out the jamsbecause this old-school handling is dull. This is the first Yamaha we have tested since 1996 that caused test riders to grumble about the way it felt in a straight line.

(3) Grips: Unless you have gorilla-sized hands, the stock Yamaha grips feel big. Plus, they gave us a nasty case of Yamathumb.

(4) Titanium footpegs: We’d be willing to trade the titanium footpegs in for 57mm steel pegs. Until then, Lightspeed will sell you a set for $99 at (714) 990-5767.

 

Q:WHAT DID WE LIKE?

 

A:The like list:

(1) Plastic. Finally, after eight years, a Yamaha that doesn’t look identical to the year before. To maximize the difference, we opted for the ultra-hip retro yellow and black.

(2) Shock: It’s more trick than most works kit shocks.

(3) Power: The YZ250F is still the only 250 four-stroke with equal amounts of bottom, mid and top.

(4) Tires: For years Yamaha delivered the YZ250F with hard-pack Dunlop 739 tires. The solid-performing 739 stays on the front, but the rear is replaced with a 756 that’s much more multipurpose.

(5) Suspension: SSS is better than AOSS.

(6) Handlebars: In a world that is totally dominated by Renthal, it’s nice to see ProTaper get an OEM gig.

(7) On-the-fly clutch adjuster: The big-boy adjuster is much easier to use.

 

Q:WHAT DO WE REALLY THINK?

 

A:We prayed for an aluminum-framed YZ250F for 2006. It’s here. Always ready to look a gift horse in the mouth, now the MXA wrecking crew is praying for taller handlebars, cultivated handling and a completely new engine for 2007.

 

For more 2006 Bike Tests, go to Top Ten Stories

2006four-strokeyamahayz250f