The YZ450F was our 2017 Motocross Shootout winner, so when Yamaha came out with an all-new bike for 2018 we were excited to see if it raised the bar for the class even higher.

This article was originally published in the October 2017 issue of Dirt Rider.

A powerhouse since 2010 when the Yamaha engineers reversed the engine and created a straighter, downdraft intake, the new YZ450F gets a slightly straighter (more vertical) intake tract and higher-lift cams. The intake valves now open earlier, open farther, and stay open longer, with the aim of increasing midrange and giving a torquier character. Overlap, when both valves are open, has been increased in an effort to improve top-end and over-rev. The throttle body is now a Mikuni unit (a switch from Keihin), with a push-on cold-start knob that releases with a twist of the throttle. The piston is now a bridge box style, lighter by 2.3 percent and with a compression bump (12.8:1 versus 12.5:1), and the new exhaust header is 12mm longer and narrower at the junction (38mm diameter versus 41mm). There’s even a new spark plug with a longer electrode for improved burn efficiency and a cap holder on the valve cover. According to Yamaha, the changes mean an overall horsepower boost and claimed 3 more ponies at both 6,000 and 9,000 rpm.

The clutch pressure plate is redesigned with more rigidity in its outer area and less at its center, the clutch’s steel plates are precision ground on both sides, and the springs are designed to stay straighter during compression for smoother engagement at high rpm (such as launching off the starting gate. Yes, the bike still has the Launch Control System). Also second, third, and fourth gear cogs are 1mm wider (the ratios are unchanged) for durability with the stronger engine output.

2018 Yamaha YZ450F
The overall character of the 2018 YZ450F's power still retains some traditional four-stroke personality.Jeff Allen

Oh, and there’s that magic button on the handlebar. The engine is electric-start only (it will start in gear with the clutch out), with a starter that is more compact than the one on the FX line, with a claimed 70 percent more cranking power and drawing 20 percent less electricity. As a bonus you might not normally think about, because the bike now has a battery, Yamaha was able to decrease the ignition’s electrical output and therefore decrease the drag the system puts on the engine, which Yamaha reps claim improves low-rpm power and response.

An all-new frame has main spars that are now straight, and the frame is narrower at the rider’s ankles. The engine is held 2 degrees more vertical, and the engine hangers now attach at the rear of the head and are aluminum rather than steel. The steering stem is 6mm forward, the triple clamp offset changes from 25mm to 22mm, and the handlebar mounts put the handlebar 5mm higher.

Yamaha moved the radiators, shrunk the gas tank, and redesigned the shrouds in an effort to slim down the bike to the tune of 16mm narrow at the shrouds and at the "pocket" of the seat. The new airbox and filter are still tool-less, now with one Dzus fastener for the cover and clips to hold on the filter. The seat is 8mm lower at the front and 19mm lower at the rear. Combined with the taller bar mounting, one test rider felt the bike was a little "choppered out" until he rolled the handlebar back a little. The bar bend is the same but the bar is lighter, and the rims (they are blue on the blue bike) are lighter too.

Yamaha put Wi-Fi on the bike and its power tuner on your smartphone (just download the free app). The adjustment grid is now 4 x 4 instead of 3 x 3, and the tuning values can be adjusted to focus the tuning to a narrower rpm range. Fuel is adjust­able richer or leaner up to 14 percent, and ignition can be retarded 9 degrees or advanced 4 degrees from stock. Riders can quickly pick from three stock maps, create their own maps, share maps, and try maps that the Yamaha test team shares. For paranoiacs worried about their bike getting hacked or a transmission inter­ception, the app is password protected, only two phones at a time can be tied to any given bike, and the bike’s system must be powered up but with the motor off. The tuner also has a race log to organize your best settings.

Even the suspension got some updates. The fork’s cylinders and pistons are up 1mm to 25mm, and the mid-speed valves and pistons are updated. The shock’s subtank capacity is increased 30cc, and its spring is lighter in weight and one rate stiffer (from 56 to 58 N/mm). The fork rate remains at 5.0 N/mm.

2018 Yamaha YZ450F
The new, slimmer bodywork of the 2018 YZ450F is a great improvement.Pete Peterson

Engine

With 450cc of displacement, a bike in this class can have too much power, and that was a criticism of the previous-generation YZ-Fs for some riders—maybe not too much but “too much too soon.” The 2018 machine does a better job of making that horsepower more usable without making it less potent. Yamaha has smoothed not just the off-idle hit but also the full power delivery up through the rpm.

Nearly every rider commented the power down low was strong, but more importantly it was accessible and no longer abrupt or overly snappy. The smooth and tractable feeling continues through the revs, making the bike easy and fun to turn with the throttle in the flat corners and also meaning riders could rely only on throttle input and leave the clutch alone in corner ruts.

The overall character of the power still retains some traditional four-stroke personality with a tractor-y feeling compared to some of the other bikes in the class. It’s one of those deceivingly strong engines where you might find yourself launching farther than the rpm suggested you would. The most usable portion of the powerband was the low to mid, yet some testers com­mented the bike needed to be shifted a lot for a 450, with first gear being especially short.

MSRP: $9199
Weight (tank full): 248 lb.
Seat height: 37.25 in.
Fuel capacity: 1.6 gal.
2018 Yamaha YZ450F
The engine is held 2 degrees more vertical, and the engine hangers now attach at the rear of the head and are aluminum rather than steel.Pete Peterson

Suspension

Yamaha has held the top spot in suspension action and feel for about a decade, and blue shows no signs of making a misstep. Yes, the 2018 YZ450F has outstanding suspension.

Probably the best word used to describe the suspension feel is “buttery.” The Yamaha makes the small track imperfections disappear and gives almost a magic-carpet ride over the chattery stuff. More great news, many testers felt the bike needed no adjustments to make the suspension feel just right for them; the stock settings suit a wide range of riders.

There were, however, two pro-level testers who complained of a harshness transferred to their palms, with one saying he also felt a mid-stroke step in the fork. These same pros felt a sort of “bounciness” in the fork at corner entries. These two criticisms were almost lost, however, in the list of praises for the suspension feel, as most riders, heavy and light, novice to expert, felt the bike was plush and also handled the big hits amazingly well.

The YZ-F has a sit-in (rather than sit-on) feeling that allows the rider to feel a part of the bike; it’s more of a machine the rider charges around the track rather than finesses, manipulates, or manhandles. The previous YZ450F had a very big and sometimes uncooperative attitude; this new bike is much more eager to listen to the rider. It’s lighter feeling on the track, and some riders even said it had a 250-ish feel, though it still has some of that “significant” feel of the previous bike.

But the big YZ-F did draw some handling criticisms of headshake at corner entrances from a few testers, while others felt no trace of it. It was mostly limited to a twitchy front end under braking when entering high-speed corners. One pro tester had a big problem with this, but a sag change down to 107mm then going two stiffer on fork compression and four slower on fork rebound remedied the problem. Another lighter, fast tester cured the corner-entry twitchiness by going just three clicks slower on fork rebound. There was also a few mentions of a front end that wanted to climb out of ruts or just give a vague feel in corners.

2018 Yamaha YZ450F
"It’s more of a machine the rider charges around the track rather than finesses, manipulates, or manhandles."Jeff Allen

Most riders felt they could put the bike right where they wanted on the track, with comments that it rolled well through the corners, that it had a calm, predictable nature, and that it had great stability on straights and jump launches. One pro rider even said the bike almost seemed to adapt to him and the track conditions, necessitating no suspension tuning.

All our testers felt Yamaha’s new slimmer bodywork was a great improvement, though some wanted it to be even thinner, and many felt the bike was slim and great while standing but once sitting to corner the shrouds pushed their legs out too far. One rider found the left header interrupted his grip on the bike, while another felt the bike’s sides had an overall slick feeling and would use grip tape if it were his personal bike.

The clutch was praised and the Yamaha is a clean-shifting machine, and the brakes were loved for being strong and easy to modulate.

2018 Yamaha YZ450F
2018 Yamaha YZ450FPete Peterson

Conclusion

Yamaha built a better 450. The power is more manageable without losing any thrust. The suspension action has been the class benchmark for about a decade, and that has not changed. If you are looking for a bike that can be plush and handle the big stuff, this is your ride. But the same backward engine that helps the power can throw off the handling for some riders. We had three trackdays on the bike with nine test riders when this story went to print, but we’ll happily keep spinning more laps to learn more between now and this year’s shootout. It will be exciting to see if Yamaha can stay on top with its new machine.

What's Hot

  • Plush suspension that still handles bigger impacts
  • Strong power is more manageable in the low-end
  • Electric start and Wi-Fi tuning

What’s not

  • A few riders had headshake on corner entry
  • Still a wide and significant-feeling bike
  • Bike gained weight
2018 yamaha yz450f
The 2018 Yamaha YZ450F continues to set the bar in regards to suspension.Jeff Allen

Opinions

Michael Wicker
Age 20, 5'9", 140 lb., National B Class Motocrosser
The handling and stability through bumps was amazing on this bike, which I felt gave me more comfort. The power is more balanced and not so harsh on the bottom-end, something that I felt with the 2016 and 2017 models. In the corners I felt a vague feel, something I couldn't really fix by adjusting the suspension. The [performance] style of this bike is really more for a structured rider, not so much the more loose and aggressive type of rider. The overall feel of the bike was amazing, and I am definitely seeing huge improvements from Yamaha.

Allan Brown
Age 47, 5'10", 175 lb., Vet Intermediate
The motor on the Yamaha is just a tractor; you just put it in third gear and go. The suspension has a plush, "gooshy" feel. I'm disappointed in the gas tank, in that they didn't slim that down more. That would help the bike feel a lot narrower. I don't think the radiators are as big of an issue as people think. You definitely sit in the bike and you're driving it; it feels like you're a part of it more than most bikes. It's a little lazier, a little slower in the responsiveness compared to some of the razor-sharp bikes, but that makes the Yamaha easier to ride. The YZ-F feels planted everywhere, it gets good traction, it's predictable, and it's fun to ride.