2015 Yamaha YZ450F Review
ECU and suspension tweaks help the Yamaha YZ450F deliver on the promise it showed last year
Yamaha attempted to defy conventional wisdom in the 450cc class when it introduced an entirely different YZ450F in 2010. The all-new YZ’s rearward-slanted cylinder and reversed cylinder head engine architecture, while not completely original, was a radical departure from the contemporary crop of 450cc contenders.
2015 Yamaha YZ450F
Too bad you wouldn’t know it on the track, as the new-gen YZ450F failed to dominate the class in comparison tests, and has yet to win an AMA national motocross or supercross title. Ironically, the same can’t be said of its little sister, the YZ250F. Yamaha rolled out the 250 last year as an all-new machine with the same engineering design features that the 450 has had for the past four years, and wham-o! The 250F is currently the top dog in its class and has the Lucas Oil Pro Motocross Championship number-one plate to prove it. It also took our MOBO award for Best Off-Road/Dirtbike of 2014.
Doesn’t seem fair. How is it that the YZ250F succeeded where the YZ450F hasn’t? Yamaha officials say that it has simply taken the buying public time to embrace the company’s radical dirt design, but we say it’s more a case of Yamaha needing time to sort out the chassis and suspension in order to harness the YZ450F’s awesome power.
Alas, Yamaha may finally have a handle on things with the 2015 YZ450. After spending time with Yamaha to sample the bike at Cahuilla Creek Motocross Park near San Diego, we can definitely report that it is the best-handling YZ450F in the rearward-slanted-cylinder era, and it is worlds better than last year’s model. Yamaha clearly intends to capitalize on that by making a big push in 2015, having reportedly signed Muscle Milk Honda rider Justin Barcia and RCH Suzuki rider Weston Peick to factory contracts in the Monster Energy AMA Supercross Series and the Lucas Oil Pro Motocross Championship. The YZ450F should be a great platform to let them strut their stuff.
After completely redesigning the 2014 YZ450F, Yamaha engineers made only minor tweaks to carry it over to 2015. During our 2014 Yamaha YZ450F test, we noted that its liquid-cooled fuel-injected, 449.7cc DOHC Single was strong from bottom to top, but that its low-end throttle response was not up to par until we tweaked its ECU with Yamaha’s aftermarket GYTR tuner to richen the fuel curve. We also complained that the YZ450F’s chassis was nervous at high speeds because its fork would dive over bumps. Yamaha has addressed these issues, and more, with the 2015 model. At $8590 it costs $100 more than the 2014, but the changes make it a better value than last year’s bike.
Not much has been done to the YZ450F’s powerhouse engine, and not much needed to be. Its 97.0 x 60.8mm bore and stroke is the same as last year’s model, and it retains all of the changes made to improve its power delivery over the 2013 model. They include a larger airbox, 1mm-larger (37mm) titanium intake valves and 0.5mm-larger (30.5mm) exhaust valves, along with reshaped intake and exhaust ports and a slightly increased combustion chamber volume. However, Yamaha engineers have incorporated new ECU and ignition settings to improve the 450’s throttle response as well as give it more low-end torque and better top-end overrev than the 2014.
The changes made to the YZ450F’s chassis and suspension also seem to be relatively minor. For starters, Yamaha changed the thickness, shape and material of the lower motor mounts to retune the flex characteristics of the 450’s Bilateral Beam aluminum chassis. The new mounts are made out of steel rather than aluminum, but they are also 2mm thinner and feature a U-shape rather than a triangulated shape. Corresponding changes were made to improve the 450’s 12.2-inch travel, 48mm KYB Speed Sensitive System (SSS) front fork: Its outer fork tubes are less rigid than before, and the fork spring stiffness has been increased to 5.0 kg, up from 4.9 kg. Out back, the 450F’s fully adjustable KYB monoshock also received minor setting changes to keep its 12.4 inches of rear wheel travel working in harmony with the fork.
Cahuilla Creek has a blazing-fast track layout, with sandy terrain that features deep berms and big jumps, just the right kind of place to reveal whether the changes Yamaha made were the right ones. Our ace test pilot, Ryan Abbatoye, was the same man who delivered our impressions of the 2014 model, so we knew that he would be able to discern whether these differences were just differences or actual improvements.
Right off the bat, Abbatoye said the YZ450F’s revised fuel and ignition curves yield a much cleaner power output. The big motor’s trademark torque is as broad as ever. Right from the hit of the throttle, it lunges like a Top Fuel dragster, and it can keep pulling while holding the same gear a lot longer than other bikes in its class. The power builds smoothly yet forcefully all the way to the rev limiter, and thanks to the ECU tweaks, it does so without any hesitation in throttle response through its Keihin 44mm throttle body.
We put our test bike on the dyno to see what kind of power it was making, and came away impressed. The YZ450F topped 52 rear-wheel horsepower, settling in at 52.3 hp at 9000 rpm, with 31.7 lb-ft of peak torque at 8250 rpm. Even more impressive is that the 450 motor maintains 30 lb-ft of torque from 6250 rpm all the way past 9250 rpm before it begins to tail off, and the engine maintains 50 hp from 8500 rpm all the way to its 11,000 rpm rev limit. That’s big power!
Abbatoye clearly had a lot of fun blowing up Cahuilla Creek’s sandy berms and rocketing over its big jumps on the YZ450F. We could see the grin through his helmet, and we weren’t sure if he was ever going to come back off the track.
“This bike is definitely a lot snappier than before, and it makes so much power that it is easy to ride in a higher gear now,” Abbatoye said. “Remember last year I said I felt like I wanted to be in between gears in the transmission a lot? Not this year. I really like it! It makes pro-level power, but the average rider can just ride it a gear high, and it still makes plenty of torque to launch off the corners and over jumps.”
Part of the motor’s smoother feel is also the result of a slight gearing change. Yamaha dropped one tooth off the rear sprocket, going from 49 teeth back to 48 teeth, same as was used on the 2013 model. Not only is the 450F’s motor so brawny that it can easily pull the taller gearing, but the revision actually matches the ratios in its five-speed transmission to the power curve better. When you do need to bang a shift, the 2015 will feel smoother than last year’s, as well, because Yamaha changed the bearing on the gear stop lever from a ball-bearing-style to a positive roller bearing. If you want to stay in a taller gear, there’s no need to worry about brutalizing the YZ450F’s clutch out of corners. It can take the abuse. Yamaha improved it in 2014 by adding 10%-stiffer clutch springs and new clutch plate friction material. So, hammer away.
Speaking of hammering, Abbatoye also noticed a big difference in the way the 2015 YZ450F tracks through corners and handles bumps at high speed – even though its basic chassis numbers are the same as 2014. Yamaha claims a wet weight of 245 lbs., but our test unit actually tipped the scales at 248.5 lbs., placing 119.4 lbs. on the front wheel and 129.1 lbs. on the rear wheel. Its numbers may be unchanged, but the tweaks made to its chassis and suspension have definitely yielded much better feedback than last year’s bike. Whereas the 2014 model exhibited slightly heavy steering and high-speed jitters even after we made changes to dial-in its suspension, the 2015 version can rocket into corners easier, the excess front-end dive has been eliminated, and the suspension responds much better to clicker adjustments.
“Once we set the sag, it felt pretty balanced, maybe just a little stiff overall for someone my weight (170 lbs. in full riding gear),” Abbatoye said. “We softened up the compression in the front and went out a little bit on the high-speed (compression adjuster) at the rear, and that worked pretty well over any of the bumps I hit at Cahuilla. It turns really well, but coming out of a corner, you have to be careful with how you feed the throttle because it wants to wheelie, so you want to make sure that you don’t get lazy. You need to stay over the front and control the bike.”
The same 250mm front and 245mm rear rotors used on the 2014 YZ450F are found on the 2015, and that’s fine. While Yamaha has yet to step up the diameter size on its front rotor, the Nissin twin-piston front brake does a fine job of hauling the bike down from speed. The same can be said for its single-piston rear brake. They’re linear and strong without being snatchy. For 2015, Yamaha has fitted the black-anodized Excel rims from the YZ250F shod with Dunlop’s excellent new-gen MX52 tires. The MX52s are designed to excel in medium to hard terrain, yet they worked well in the Cahuilla sand, delivering excellent traction and very good feel. Call us spoiled, but we just happen to know that the MX32s work even better.
Yamaha has worked overtime to centralize the YZ450F’s mass, and its efforts have yielded an extremely slim and compact cockpit. Hiding the fuel filler neck for the mid-mounted 2.0-gallon fuel tank allows the rider to climb farther forward on the slim seat, more so than on other brands, making the bike easier to crank into turns.
Of course, the YZ450F’s styling is worth noting as well. Its slim bodywork is adorned with “bold new” graphics, but what is cool about the Yamaha is the graphics are actually embedded in the radiator shrouds, which makes them much harder to peel, and thus more durable. Other detail changes include new Dzus-fasteners with pull tabs that allow the air box lid (or the top of the faux fuel tank) to be removed without requiring a tool.
Once again, the YZ450F is available in two color schemes: Team Yamaha Blue/White or the White/Red that recalls Yamaha’s old international racing colors. Both machines also get a snazzy new D.I.D. chain with gold-anodized plates and a new corrosion-resistant coating.
The 2015 YZ450F isn’t mechanically much different than the 2014, but the minor improvements Yamaha made are so substantial that it almost feels like it is a generation removed from the ‘14. The changes Yamaha made really help the 450 live up to its true potential, and they might just be what the YZ450F needed to put it over the top.
2015 Yamaha YZ450F Specifications
|Engine Type||449.7cc liquid-cooled DOHC 4-stroke; 4 titanium valves|
|Bore x Stroke||97.0 x 60.8mm|
|Fuel System||Yamaha Fuel Injection (YFI), Keihin 44mm throttle body|
|Ignition||Transistor Controlled Ignition|
|Horsepower||52.32 rwhp @ 9000 rpm|
|Torque||31.74 lb.-ft. @ 8250 rpm|
|Transmission||Constant-mesh 5-speed; multiplate wet clutch|
|Front Suspension||48mm Show SFF-Air inverted telescopic fork, fully adjustable, 12.2 inches of travel|
|Rear Suspension||Link type w/Showa piggyback reservoir shock, fully adjustable, 12.2 inches of travel|
|Front Brakes||KYB Speed-Sensitive System, inverted fork; fully adjustable, 12.2-in. travel|
|Rear Brakes||Monoshock, adjustable preload and rebound damping, 12.4-in. travel|
|Front Tire||250mm rotor disc brake w/two-piston caliper|
|Rear Tire||245mm rotor disc brake w/single-piston caliper|
|Claimed Wet Weight||245 lbs|
|Measured Wet Weight||248.5 lbs (48% front/52% rear bias)|
|Fuel Capacity||2.0 gal|
|Colors||Team Yamaha Blue/White; White/Red|