This check concerning the 2006 Yamaha YZ250 was within the 2005 October challenge of Motocross Motion Journal. Get your MXA subscription as we speak.
The YZ250 is the poster boy of the two-stroke world. Yamaha deserves props for the technical effort they put into designing, constructing and selling the aluminum-framed YZ250. The powers-that-be at Yamaha have a rep for going towards the grain–and being richly rewarded for his or her contrarian considering. Yamaha was the primary main producer to construct a hardcore four-stroke motocross bike. On the time, the 1998 YZ400 was deemed folly by the opposite members of the Massive 5. However, it modified the face of the game. Then, in 2005, Yamaha completely redesigned their two-strokes with a artistic plug-and-play aluminum body. Provided that two-strokes have been dying on the vine, Yamaha’s funding in two-stroke know-how was thought-about suicidal by their rivals, who have been slicing again, not gearing up. Shock! Yamaha bought 50 % extra YZ250’s in ’05 than they did in ’04. In the long run, Yamaha’s daring transfer elevated their market share within the two-stroke world–market share they stole from each different model.
Yamaha rolled the cube in 2005 with the YZ250, and the 2006 Yamaha YZ250 is the results of Yamaha’s gamble.
Q: IS THE 2006 YZ250 ENGINE FASTER THAN THE ’05?
A: No, it isn’t quicker than the 2005 YZ250 engine. It’s not even quicker than the 2004 YZ250 engine. Heck, it’s not even quicker than the 2003 YZ250 engine.
Q: DID YAMAHA MAKE ANY CHANGES TO THE 2006 YZ250 ENGINE?
A: In terms of elements, items and porting, the 2006 engine is a repeat of the ’05 engine, which was similar to the ’04 engine, which was a carbon copy of the ’03 engine. Don’t fret, it’s totally different from the 2002 Yamaha YZ250 powerplant.
Q: DOES THE YZ250 HAVE THE BEST ENGINE IN THE SPORT?
A: The right reply is sure, however you would make the case that the 2004 Suzuki RM250 powerband provides it a run for its cash.
Q: WHICH ENGINE IS BETTER? THE YZ OR RM?
A: The MXA wrecking crew is cut up on this matter. Half of the check riders favor the broad, responsive and tractable YZ250 powerband. It makes superior energy at each level on the curve. It cracks 30 horsepower at an ultra-low 5700 rpm (the RM250 doesn’t break 30 horsepower till 6400 rpm), peaks out at 46.four horsepower at 8600 rpm (our 2006 RM250 made 46.2 at 8500 rpm) and doesn’t surrender the ghost till 9700 rpm (the RM backs down at 9800 rpm).
The distinction between the 2 engines isn’t mechanical. Why not? That’s easy. The Suzuki RM250 is as shut a replica of the YZ250 engine as Suzuki might make with out getting legal professionals concerned. Apart from energy valve actuators, the RM250 cylinder is a clone of the YZ250 jug.
The place they differ is in philosophy. The YZ250 is the King of Breadth. Its energy builds proper off the underside and churns by means of an extended meaty pull. The RM250 is the King of Quickness. Its energy comes on faster and turns over quick. It’s snappier, however not as broad.
Which is best? It will depend on the check rider’s private style. Ginger or Maryanne?
Q: WHAT ABOUT THE JETTING?
A: Yamaha performs their jetting recreation playing cards very near the vest. On a heat day the jetting is ideal, however in chilly climate or underneath a load, it tends to be on the lean aspect. For many conditions, elevating the needle will work, however in the event you add an aftermarket pipe, journey in sand, or experience at elevation, you’ll want a much bigger fundamental.
Q: HOW GOOD IS THE YZ250 GEARING?
A: We added one tooth to the rear sprocket. It punched up the acceleration in second gear and introduced third into play sooner. Quicker riders, featherweight riders and quick tracks work greatest with the inventory gearing.
Q: ARE THERE ANY CHANGES TO THE YZ250’S ALUMINUM FRAME?
Q: ARE THERE ANY CHANGES TO YAMAHA’S ROLLING CHASSIS?
A: Yamaha made ten modifications to the 2006 YZ250.
(1) Suspension. The fork and shock are completely new for ‘06.
(2) Shock spring. All 2006 YZ’s may have titanium shock springs. They save over a pound.
(three) Entrance brake lever. Yamaha redesigned the entrance brake lever to take away the skinny portion by the rider’s index finger.
(four) Fast-adjust. The on-the-fly clutch adjuster will get a a lot bigger quick-adjust knob to make it simpler to control.
(5) Triple clamps. The handlebar mounts are adjustable (throughout a 10mm vary by rotating the bar mounts), and the fork tubes are 2mm farther aside for elevated stability.
(6) Rear brake caliper. The rear brake caliper has been lowered for extra clearance towards the silencer. The pad materials and bleed screw are up to date.
(7) Saddle. Yamaha used softer seat foam for 2006, however they added 10mm extra of it to the middle of the seat.
(Eight) Plastic. There’s a new entrance quantity plate and entrance fender. You’ll be able to inform a 2006 entrance plate from the previous model by the crease down its centerline.
Q: ARE KAYABA SSS FORKS BETTER THAN SHOWABA AOSS FORKS?
A: How good are you at deciphering Yamaha’s acronyms? Have you learnt what BASS, YPVS or AOSS imply? BASS stands for Brake Assisted Suspension System. YPVS is Yamaha Energy Valve System. AOSS was Air/Oil Separate System. BASS and AOSS are historic historical past–although AOSS was brand-new in 2005. What replaces AOSS? The acronym SSS.
Kayaba’s 2006 damping system is labeled SSS (Velocity Delicate System). We’re completely happy to say that speed-sensitive damping is an enormous plus for Kayaba’s forks.
Q: WHAT’S SO HOT ABOUT THE SSS VERSUS the AOSS?
A: There are two forms of damping: position-sensitive and speed-sensitive. Final yr’s AOSS forks have been 70 % position-sensitive. What does that imply? The damping charges have been dictated by the place of the fork’s piston contained in the cartridge rod. In easy phrases, the farther the piston moved down within the cartridge rod, the stiffer the damping.
The 2006 Kayaba SSS forks are 90 % speed-sensitive. Switching from 30 % speed-sensitive damping to 90 % for 2006 means the forks will keep larger of their stroke, have a extra linear damping fee and resist bottoming. Velocity-sensitive damping will get its identify as a result of the damping fee is decided by the velocity at which the piston strikes by way of the cartridge rod.
Q: WHAT IS LINEAR DAMPING?
A: With each mannequin yr, Yamaha has tried to reduce the YZ fork’s tendency to backside. The SSS’s speed-sensitive damping is an all-out assault on the longtime YZ bugaboo.
Yamaha’s speed-sensitive damping has a extra linear damping curve. A linear curve will get steadily firmer because it goes. It will get stiffer on the similar fee within the first half of the journey as within the second half. That is night-and-day totally different from the 2005 AOSS fork’s progressive damping curve. Final yr’s progressive curve began out very mild, remained mild via the midstroke, after which all of the sudden obtained a lot stiffer in a brief time period.
Q: WHAT IS WRONG WITH PROGRESSIVE DAMPING?
A: The issue with a progressive damping curve is that the fork tends to hold down within the first half of its journey (courtesy of the sunshine damping). When a fork hangs down in its stroke, it makes use of up potential bump absorbing journey. Yamaha’s aim with the SSS forks is to have firmer damping at the start of the stroke in order that the fork doesn’t react like a runaway practice on the finish of the stroke. The 2006 YZ250 fork rides larger within the stroke over small bumps, in order that it will probably re-cock to its most journey extra absolutely in preparation for giant hits. This balances out the chassis underneath acceleration and eliminates diving beneath braking.
In our opinion, the SSS forks are higher on each measurement bump and work with the chassis as an alternative of towards it. The damping is regulated in such a approach that the spring price had been decreased from zero.44 kg/mm to zero.43 kg. They resist bottoming, take up little bumps and don’t get harsh over the medium-sized stuff. The typical rider ought to begin with the compression on 12 out and the the rebound on 10 out.
Q: WHAT ABOUT THE SHOCK?
A: Yamaha is providing one thing particular for 2006–works know-how. YZ250 house owners will get three manufacturing unit tidbits instantly off of Chad Reed’s YZ250 shock.
(1) The 2006 shock has an 18mm shock shaft. It’s 2mm bigger than final yr’s shock shaft. The bigger shock shaft diaplces extra oil, which signifies that extra oil is pushed by means of the valving sooner, which leads to a extra delicate really feel on small chop.
(2) All of the internals elements of the YZ250’s Kayaba shock are Kashima-coated to scale back friction. As well as, the shock reservoir has been elevated in quantity by 30 % bigger reservoir to assist management the warmth
(three) The shock spring is comprised of titanium, however not simply any titanium. This isn’t porous Russian Ti or low-dollar Chinese language metallic, it’s high-quality, aircraft-grade, American-made, titanium wire that’s shipped to Japan for coiling. It’s rated as a four.9 kg/mm spring.
It’s a excellent shock. We ran the race sag at 100mm, high-speed compression on one end up, low-speed compression on 11 clicks out and rebound on 9 clicks out.
Q: HOW DOES THE YZ250 HANDLE?
A: In the event you favored final yr’s YZ dealing with, you’ll like this yr’s chassis as a result of the top angle, path, entrance middle, wheelbase and rake are equivalent.
YZ dealing with it’s thought-about the benchmark as a result of it doesn’t do something incorrect. It doesn’t commerce straight-line stability for turning prowess (just like the RM250). It doesn’t commerce turning prowess for straight-line stability (just like the KTM 250SX). It doesn’t search quickness at the price of accuracy (just like the KX). It doesn’t favor rigidity over suppleness (just like the CR250).
The YZ250 is a secure platform that’s amazingly correct at turn-in. It requires virtually no mid-turn correction from center-out to exit. It isn’t the most effective dealing with body in each class. It isn’t the quickest turning. It isn’t probably the most secure at velocity. As an alternative, the YZ250 has simply sufficient of the whole lot to make it a terrific all-around package deal.
Q: WHAT DID WE HATE?
A: The hate record:
(1) Graphics: You possibly can’t get a 50th Anniversary yellow-and-black YZ125 or YZ250. The anniversary editions are fo the four-strokes solely. Too dangerous.
(2) Rear brake pedal: For some purpose it was tucked in an excessive amount of. We bent it out to make it extra accessible.
(three) Titanium footpegs: We’d be prepared to commerce the titanium footpegs in for 57mm metal pegs. Till then, Lightspeed will promote you a set for $99.
(four) Shock spring: In the event you weigh over 180 kilos you will have a stiffer shock spring.
Q: WHAT DID WE LIKE?
A: The like record:
(1) Suspension: SSS is best than AOSS. Though we’d like to provide BASS one other shot.
(2) Bar mounts: Lastly the bar mounts are detachable. That signifies that you don’t have to purchase a brand new prime triple clamp to modify to 1-1/Eight-inch bars. Moreover, the inventory mounts may be rotated ahead 10mm.
(three) Handlebars: Renthal, sufficient stated.
(four) Rear tire: The D739 exhausting monitor tire has been changed by a intermediate terrain D756.
(5) On-the-fly clutch adjuster: The large boy adjuster is far simpler to make use of.
Q: WHAT DO WE REALLY THINK?
A: This can be a treatment for the four-stroke doldrums. You understand the signs. You possibly can’t get the droning of four-strokes out of your head. You crave kick-in-the-pants acceleration. You need a bike that’s 13 kilos lighter and doesn’t stall within the corners. Our prescription? Pop one Yamaha YZ250 beneath your fanny and kiss the doldrums goodbye.