Yamaha unveiled their 2018 line-up of off-road motorcycles with minor updates across the board, but the big news is an all-new YZ450F — a motocrosser you can not only start with the push of a button, but also tune with a tap of a touch screen.
The Blu Cru’s new open-class motocross machine truly is all new, with changes to the engine, frame, and bodywork, in addition to new technology. Two decades ago, Yamaha made history in AMA Supercross with the first race win by a four-stroke, with Doug Henry winning in Las Vegas on a prototype. (If you missed Brett Smith’s excellent story last month, it’s well worth a read.) A year later, that prototype became the YZ400F — the first modern production four-stroke MX bike. Eventually, the other manufacturers caught up, but for a few years, Yamaha was king. So, what are they doing now to continue that legacy?
New technology in the 2018 Yamaha YZ450F
The YZ-F was a pioneer not just in creating the market for four-stroke motocrossers, but also with other innovations, such as the introduction of the reversed cylinder design in 2010. (That had been done before, most notably by the disastrous Cannondale MX400 of the early 2000s, but Yamaha’s was by far the most successful implementation.)
For 2018, Yamaha is debuting another industry first on its flagship motocrosser — but this time you’ll need your smartphone to reap the benefits.
Now available is the “Power Tuner” app for your Apple or Android phone. Previous generations of the big YZ had a $290+ accessory called the GYTR Power Tuner, a plug-in fuel injection and tuning tool. Now, all that functionality is available on your phone for free, so you can make changes to ignition timing and fueling via Wi-Fi.
Fueling is done via a four-by-four grid, and one unit on the grid translates to a two percent change. You can increase or decrease fuel injection up to 14 percent. Ignition timing is also handled through a grid, and you can make changes between a range of -9 to +4 degrees.
In addition, you can keep a race log with notes and save settings for the map that worked best for you, monitor functions like rpm, throttle position, battery voltage, coolant temperature, and more in real time, set reminders for maintenance based on engine hours or calendar dates, and scan for diagnostic codes.
Be warned — the connection is secured with a password that’s displayed on a control box which is accessible once you pop off a number plate. If any of my friends buy a new YZ450F, my new mission will be to find the password and screw with them by adjusting the timing and dropping down the amount of injected fuel by 14 percent. That’s what friends are for, right?
The other big change is the addition of an electric starter. The kick-start lever has been removed but you can order one as an option if you don’t trust magic buttons. The starter is driven off a 2.4Ah, 13.2-volt battery that weighs just 1.5 pounds. The starter motor is center-mounted and features a damper to prevent damage from engine kickback.
Beyond the new tech and electric start, Yamaha introduced a variety of changes in the never-ending pursuit of more and better power and less weight.
2018 Yamaha YZ450F: The engine
The motor continues the rearward-slanted cylinder design introduced in 2010 (intake up front and the exhaust at the rear of the cylinder), though it’s now 6.2 degrees off vertical, compared to 8.2 degrees last year. The piston has been updated with a bridge box design that allows for a 2.3 mm thinner crown and a six gram (2.3 percent) weight reduction. This may seem like a small number, but it’s significant when you’ve got mass rotating up to 12,000 rpm. The compression ratio has been bumped up from 12.5:1 to 12.8:1. Yamaha says that the counterbalancer nullifies 96 percent of the reciprocating mass, meaning less vibration for you to deal with.
Mikuni takes over from Keihin as the throttle body supplier of choice with a unit that’s 12 percent lighter, though the basic specs remain the same: 44 mm diameter with a 12-hole injector. What’s new this year is a push button actuation for the cold start system. Push the button in and the system raises rpm for cold starts. Cleverly, the next time you completely close the throttle, the cold start system shuts itself off and the button pops back out.
The long list of changes for more power even reach the spark plug, which now gets a longer electrode to get deeper into the combustion chamber for a better charge burn.
Launch control carries over from last year’s bike, but several small changes have been implemented to make power delivery more controllable at low and medium rpm while increasing power at the top of the rev band. The intake ports have been straightened and the camshafts have been reshaped to increase the valve openings (+0.5 mm intake, +0.4 mm exhaust). Because of this, the valve timing overlap has increased by eight degrees, which helps intake gases chase out the exhaust. The exhaust gases flow out into a 12 mm longer head pipe which has a smaller junction to the muffler than before (38 mm vs. 41 mm). The muffler is now rubber-mounted and the mounting point has switched from underneath the can to above.
Yamaha also revised the clutch and transmission to help with transferring power to the rear wheel. The shape of the pressure plate has been changed to decrease rigidity in the center and increase rigidity on the outer surface. Last year’s steel clutch plates had surface grinding only on one side, whereas the new bike gets it on both sides. These changes along with new clutch springs have improved the squareness tolerance of the clutch, which translates to better alignment when the clutch is engaged and better feel in the friction zone. To make sure that the transmission can handle the increase in power, Yamaha increased the width of the gears for second, third and fourth by one millimeter each.
The all-new bilateral beam aluminum frame has two significant changes: the old hydroformed S tank rail has been replaced with an extruded straight piece, and the tension pipe has been lowered to increase the size of the triangulated absorption zone. All of the above is a long way of saying that Yamaha has been able to substantially increase the rigidity of the frame. Vertical rigidity has gone up by 25 percent, horizontal rigidity by 9 percent, and torsional rigidity by 15 percent.
The upper mounting points for the engine are now made of aluminum instead of steel and they have been moved to the rear to more equally distribute weight across all four mounts.
While the foot peg position remains the same, several minor position changes add up to a new rider triangle. The steering head pipe has been moved six millimeters forward, and the handlebars are now five millimeters higher. Last year’s YZ had handlebar mounts with four-position adjustability, and that carries through to the new model. The triple clamp offset has been decreased from 25 mm to 22 mm and trail has increased from 118 mm to 121 mm. The seat is lower by eight millimeters in the saddle and 19 mm at the rear fender. Rounding it all up, the wheelbase is five millimeters longer and the big YZ now offers five millimeters more ground clearance.
The rim profile has been tweaked but the more important change is weight savings. The front rim is now 40 grams (2.6 percent) lighter while the rear rim is 70 grams (3.8 percent) lighter. Again, they’re small numbers but it’s unsprung rotational mass. The handlebar also went on a diet, as Yamaha was able to reduce the thickness in the center and on the ends by using higher strength material. This resulted in a weight loss of 111.5 grams (17.4 percent).
KYB supplies their next generation suspension for the new YZ, which consists of larger forks (25 mm vs. 24 mm) and new internals — the mid-speed valve is now a leaf spring design as opposed to last year’s coil spring. The rear shock gets a new spring with fewer turns and thinner material, so it weighs 210 grams (4.8 percent) less. The spring rate is slightly stiffer — 58N/mm vs. 56N/mm from last year. The rear shock oil reservoir is now 30 cc larger. Both ends of the suspension have been redesigned to increase oil flow amount, which is integral to controlled low-speed damping.
From the front to the back, the new bodywork is thinner and lower. As mentioned above, the seat is lower, but it’s also 18 mm narrower. The tank is 16 mm narrower up front, but capacity is down from 1.9 gallons to 1.6 gallons. Yamaha say it’s still “plenty” for a 40-minute moto. The radiator shroud was brought in closer to make the entire bike narrower. This was done by mounting it six degrees more vertical and six mm closer to the frame. The surface area of the radiator core is up by 4.5 percent, thanks to the smaller fuel tank, and the fins on the radiator cover now vary in angle for better air flow. The rear of the front fender is narrower to let more air get through to the radiator, as well.
One of the many advantages of the reverse cylinder design is that the intake is in the front. Because of that, Yamaha places the air filter up where you’d expect to see the gas tank, far away from any roost. The air filter is accessible without any tools. Previously, you had to undo three Dzus fasteners to pop off the air filter cover, but Yamaha has simplified the process so now you just have to deal with one.
The price of progress
MSRP for the new YZ is $9,199, and it’s available in Team Yamaha Blue with blue wheels or White (with cyan accents and black wheels). If you like what you see, you can head straight to your local dealership or wait until August when Yamaha will offer demo rides through their event website. Approximately 40 Yamaha accessories will carry over from last year’s bike, and 20 new accessories specific to this model (including performance modifications like a ported cylinder head and FMF muffler) will be available starting in September.
The rest of the lineup
The WR250F also gets a few significant updates, including new cylinder head ports, higher lift camshafts, piston, piston pin, piston oil sprayer, connecting rod, throttle body joint, valve springs, head pipe, and ECU. All that is said to boost power between 4,000 to 14,000 rpm. The main frame, engine mounts, and fork seal scraper are all new, as are some minor pieces of the clutch and transmission. Like the YZ450F, the WR250F loses the kick start lever but it’s available as an accessory. MSRP will be $8,099.
The bigger brother WR450F gets a new fork with a tube scraper and different pressure piston shape. The kickstart lever has been removed (Are you sensing a pattern here?), a cover to protect electrical wiring has been added, and Yamaha now specs Dunlop MX3S as the OEM rubber. MSRP is $9,099.
|Carry-over Yamaha dirt bikes for 2018|
The YZ250FX and YZ450FX get the same Dunlop MX3S tires and electrical wiring cover. MSRPs are $7,999 and $8,999, respectively.
The YZ250F gets the same liveries as the YZ450F (Team Yamaha Blue and White). MSRP is $7,699.
All other off-road models listed above right carry over with new liveries.