2020 YAMAHA YZ450F: FULL TEST

Yamaha is deeper into the digital age than anyone, and the 2020 YZ450F has a mixture of new hardware and software to bring it into the new decade. Externally, the bike looks as it has since the really big makeover of 2018. That was when it got a new frame and motor, as well as Yamaha’s truly innovative smartphone EFI tuning system. The 2020 model has its electronic refinements, but it also got a long list of mechanical changes. For now, the days of old-world mechanical engineering are still very much with us.

Yamaha still lays claim to having the most technologically advanced motocross bike in the 450 class.
Yamaha still lays claim to having the most technologically advanced motocross bike in the 450 class.

HARDWARE STORE
There are about 15 significant changes to the hard parts in the 2020 YZ450F motor. The top end still sits almost vertically with only a slight rearward tilt, but everything from the head gasket up is new. The head is 10mm shorter from bottom to top, even though the valve angle is steeper, allowing more room in the ports. The cams are 14mm closer together and 6mm lower, and the head is 0.67 pounds lighter. The piston is also new, and the compression ratio has been upped to 13.0:1. In the lower end, the most interesting change is the switch to a 1.5mm-longer rod. Remember the old days when there was a long-rod kit for the YZ250 two-stroke? The thinking is much the same here. This changes the angle of the rod but not the stroke and not the displacement. That puts less side load on the crank and makes for a more efficient transfer of energy as the piston is driven downward. The exhaust head-pipe diameter is increased 3.2mm. There are changes in the air filter and a few other mechanical updates. As far as electronic hardware, there’s a new rectifier/capacitor unit, but the main attraction is still a Mikuni-made fuel-injection system with a 44mm throttle body and Yamaha’s Wi-Fi tuner. This feature is still exclusive to Yamaha, but it’s only a matter of time before it spreads industry-wide. The bottom line is that it takes all the extraneous junk out of the tuning process. You pull out your smartphone at the track and have at it—no laptop or dedicated electronic device needed. For 2020, the standard map is new, but all of the previous maps will still work. The 2020 model now allows on-the-fly swapping between any two maps of your choice.

The KYB components get only half of the credit for the Yamaha’s excellent suspension. The chassis is a big factor.
The KYB components get only half of the credit for the Yamaha’s excellent suspension. The chassis is a big factor.

Even though the YZ’s chassis looks the same, Yamaha tweaked some details here and there. The frame rails under the airbox and tank are made of thinner material, but only on the inside wall. The engineers are always fiddling with the flex characteristics by making these extremely subtle changes. Same thing goes for the rails under the engine. And, of course, there are minor changes to the shape and material of the motor mounts, as Yamaha loves to do each year. More obviously, the handlebar mounts have been lowered 5mm, and the standard position is now the second-most forward of the four available options. These are changes that we made to our 2019 YZ anyway. We didn’t get the taller seat that we wished for, but Yamaha did at least make the seat foam 10-percent stiffer. As a side note, there’s only 20mm of foam to start with, so a 10-percent change in stiffness makes little perceptible difference. 

 

For 2020, Yamaha gave the YZ450F motor a new head and a longer rod, among other things.
For 2020, Yamaha gave the YZ450F motor a new head and a longer rod, among other things.

In the outlying component department, there are minor fork and shock valving changes, the top triple clamp is flexier, and the front axle has a larger inside diameter with the same outer diameter. Yamaha also redesigned the Nissin brake calipers at both ends and decreased the size of the rear rotor. The bad news is that your old rear wheel won’t fit until you replace the rotor.

THE TALE OF THE TRACK
With so many changes, has riding the Yamaha become a completely new experience? No. It’s still a YZ450F; it is just a better YZ450F. The motor was already a well-mannered brute. It was fast, smooth and easy to use. Now, it’s just a little sweeter. Unfortunately, there’s no sweetness curve that we can graph out and print. It turns out that most of the characteristics that we like or don’t like about a bike’s power delivery are intangible. It’s not all about torque, horsepower and rpm. When you open the YZ450F throttle, it does exactly what you expect. There are no dead zones, soft spots or glitches—just smooth, evenly metered power. If you rev the YZ, it’s still a beast. On top, it’s no longer the fastest of the 450s, but it’s close enough for 99.9 percent of the dirt bike-riding population in the world. Most riders simply can’t hold on tight enough to keep the YZ screaming all the time, and for them, the bike can be tamed with an upshift. When you run it a gear high, the power hits a little softer, engine braking is a little mellower and the bike still runs like it should. You never get the feeling that it’s on the verge of stalling or coughing. In fact, the stock mapping is excellent this year. In the past, the Yamaha testing department offered up some maps that they developed after the production settings were finalized. In general, we’ve liked those better than the stock map or the options that were preloaded in the Power Tuner. This time, we never found anything we liked better than stock.

Yamaha’s Power Tuner is a smartphone-based app that allows you to alter the fuel-injection system. The numbers displayed here were developed by Yamaha’s testing department after the production values were finalized.
Yamaha’s Power Tuner is a smartphone-based app that allows you to alter the fuel-injection system. The numbers displayed here were developed by Yamaha’s testing department after the production values were finalized.

In case you don’t know how the Power Tuner App works, here’s a little review. Each YZ transmits a Wi-Fi signal as soon as the starter button is tapped. The bike doesn’t have to be running, but it does have to be live and humming. You connect your phone to the bike using a serial number as a passcode; that number is printed on the back box behind the left number plate. When you open the app, it will give you two charts—one is for fuel mixture, the other is for spark advance. Rpm is on the horizontal axis and throttle opening is on the vertical axis of both charts, and there are 16 values that can be altered. All of them start at zero to represent stock settings, and you can insert positive or negative numbers. That part is easy; getting to the point where you know how to get the results you want takes testing—lots of testing.
    The curve that Yamaha’s testing department offered us was all about being smooth. The power delivery was very linear, almost like a traction-control feature. Most of the tracks where we tested had fairly loose soil and good traction. For those, we liked the tanginess of the stock curve.

THE YAMAFACTS
If you performed back-to-back tests comparing the 2020 Yamaha chassis with the 2019 chassis, the various differences created by the reshaped motor mounts, the frame material and the front axle would be somewhat clear improvements for most riders. In the big picture, though, the Yamaha still handles essentially the same. It’s still a big-feeling bike that likes to be steered with the rear wheel. If you get the rear end to step out just a little when you enter the turn, the bike follows through on autopilot. It just takes a little confidence to initiate the turn. The Yamaha feels big because it is big. It still weighs 239 pounds on our scale without fuel. The KTM, Husky and Kawasaki are all lighter—and they feel lighter. A number of the changes for 2020 should have resulted in a slight weight loss, but perhaps the switch to Dunlop MX33 tires added it all back. The biggest improvement is the new handlebar position, which is lower and further forward. Now you can get over the front end a little more easily to make the front wheel stick. 

 

Just like last year, the suspension is outstanding. The fork has an amazing ability to please a very wide range of riders, from 150 pounds to over 200. That’s a little freaky and tells us it goes way beyond the settings in the KYB fork and shock. As we said earlier, Yamaha’s testing department sweats out the most intricate details of chassis flex. The changes for 2020 might not seem like much, but the cumulative effect after years of that kind of attention is obvious—and the suspension components get most of the credit. We like the rear preload on the softer side of the range, generally around 105mm of sag. If we alter the fork at all, it will be to take out a little compression damping.

STICKS AND STONES
It’s hard to break a YZ450F. For years it has earned a reputation as the most reliable motocross bike you can buy. There’s nothing about the new bike that should change that. The brakes are strong. The clutch has a great feel and an easy pull. The shifting is excellent, and the bike has the tight, solid feel of quality. Yamaha already had a huge fan base of riders who love the YZ450F. They appreciate the technology, the quality and the performance. There’s nothing about the 2020 model that will change that.

HITS
• Excellent suspension
• Easy to tune
• Super reliable
• Improved riding position
• Good-natured power
MISSES
• Overweight
• Intake noise
• Overheats quickly at idle
• Thin seat

YAMAHA YZ450F

  • Engine type: Electric-start, four-valve DOHC four-stroke
  • Displacement: 449cc
  • Bore & stroke: 97.0mm x 60.8mm
  • Fuel delivery :44mm Mikuni EFI
  • Fuel tank capacity: 1.6 gal.
  • Transmission: 5-speed
  • Lighting coil: No
  • Spark arrestor: No
  • EPA approved :No
  • Weight, no fuel: 239 lb.
  • Wheelbase: 58.5”
  • Ground clearance: 13.0”
  • Seat height: 38.6”
  •   Front Tire: Dunlop MX33 80/100-21
  •   Rear  Tire: Dunlop MX33 120/80-19
  •   Fork: KYB, adj. rebound, comp/12.2”
  •   Shock: KYB, piggyback, adj. preload,  comp., rebound, 12.5”
  • Country of origin: Japan
  • Price: $9399
  • Importer www.yamahamotorsports.com

 

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