It's well known that the popular cycle for Japanese motocross bike manufacturers consists of three production years: an all-new machine is usually followed up by two years of subtle refinements before another major change can be expected. On this schedule, the 2019 Yamaha YZ450F is in its first year of refinement, having been debuted as a completely revamped machine in 2018.
In last year's TransWorld Motocross 450 Shootout, the '18 YZ450F was praised for many things, including its amazing powerplant, class-best suspension package, smartphone connectivity, and improved cornering characteristics. In fact, more than one tester liked the big blue machine best! There were some testers, however, that still felt that the YZ's front end was a bit vague, especially when exiting corners under power, and that the suspension settings were a tad soft for more aggressive riders. This year, the revised '19 YZ450F sounds like—on paper—the perfect bike. Is it? Read on…
There are no changes to the '19 YZ450F's engine package, and that's just fine! The YZ450F powerplant is one of the most powerful, effective, and easy to tune we've ever encountered. The PowerTuner app makes it a breeze to tailor the power characteristics of the motorcycle to your exact needs and preferences. Two optional maps come pre-programmed in the app, but creating your own is as simple as changing numbers in a mapping chart. Doing so is actually educational and a lot of fun for those with the patience and desire to test; and the good news is that Yamaha has limited the parameters so that it is virtually impossible to cause damage to your machine with a wildly radical map setting. That said, the YZ450F comes programmed with a broad powerband as delivered, and there was no need to change it for '19. The engine's electric starter has been updated slightly, however, to reduce engine drag and horsepower loss. And the cylinder head's valve cover has been painted blue…
The biggest changes are revised suspension settings—front and rear—that are firmer for better hold up and traction feel. This was accomplished through revised fork and shock internal valving settings, not springs; the bike still comes equipped with a 80/100-21 Dunlop MX3S front tire and a 120/80-19 Dunlop MX3S rear tire. At the bottom of the fork, new fork lugs with a larger surface contact area and new wheel spacers, give the front end a more-rigid, precise feel. Out back, similarly designed wheel spacers give a greater area of contact with the swingarm, too.
Lastly, the Yamaha YZ450F's seat foam is firmer. The shape and height are the same; only the density has been increased. Of course, bold new inlaid graphics—this year with good-looking chrome accents—round out the package.
On The Track
We'll save the page space by saying from the get-go that we are massive fans of the Yamaha YZ450F engine and that we actually went most of the model year with a standard exhaust system on our machine. It was only towards the very end of our time with the '18 test bike that DR. D gave us a simple slip-on that actually enhanced the low-end throttle response without hurting the powerband anywhere else. That's right…every other complete system we tested last year proved not as desirable as stock for our test riders. The PowerTuner app truly does allow you to customize your powerband…for free!
The firmer suspension settings were apparent from the moment we reached race pace on the new YZ450F. Where the '18 bike in standard condition would dive under heavy braking, and exhibit more front-to-rear weight transfer under acceleration, the new bike stayed much more level and calm. We've said it before and stand by our declaration that the Yamaha's Kayaba suspension package is the best you can get on a production bike: having ridden a couple other '19 offerings it seems that this is still the case. The KYB AOSS fork is amazing in its ability to offer plush action in small bumps, great control throughout its travel, and great bottoming resistance under both slap-down and g-out impacts. The shock is equally adept at keeping the back of the machine tracking straight and tracking forward. As always, the Yamaha enjoys superb forward traction in all track conditions; we suspect it is largely due to the rearward-facing cylinder and the way it puts power to the ground.
But what about the revised fork lugs and wheel spacers? On paper, they don't seem like big changes, but we knew that the minor revisions had the potential to yield big gains. Factory race teams test the smallest, seemingly insignificant chassis changes, to fine-tune their race bikes and in comparison the lug and spacer combo is major. We were very pleased with the feeling of the YZ450F's front end when cornering. The greater rigidity of the front end provides better traction and feeling on lean in, and it tracks through the middle of a corner much better than the '18 did. Exiting corners under power remains the spot in which the Yamaha struggles, but the issue is minimal with these changes. Cornering is also helped tremendously by—believe it or not—the firmer seat foam! The '18 seat was far too soft and even allowed your butt to come into contact with the seat base under compression. The firmer foam keeps your weight where it should be, and lessens the low seat/high bars sensation last year's machine had.
In a nutshell, the 2019 Yamaha YZ450F features two main performance enhancements: the firmer seat foam and the new fork axle lugs that improve front-end performance in corners. The bike already had the best stock suspension and an engine that was tough to improve upon…could a handful of revisions make this the year that the Yamaha YZ450F regains Bike of the Year honors? Could be…
New For 2019
Updated suspension settings for an improved feeling of traction
Redesigned front fork lugs/ axle brackets for improved rigidity and front-end feel
Redesigned front and rear wheel collars for an improved feeling of traction
Updated starter system to reduce drag and horsepower loss
Increased seat foam density
Blue valvetrain cover