MXA TECH SPEC: 5 THINGS YOU NEED TO KNOW ABOUT
THE 2020-2021 YAMAHA YZ450F

(1) Ergos. The 2020 Yamaha YZ450F has the worst ergonomics of all the 2020 450 motocross bikes. It is wide, tall, bulky and heavy. And, that doesn’t take into account that it weighs 15 pounds more than the lightest bike in its class. The MXA wrecking crew focused on two areas to make the YZ450F more comfortable:

Handlebar position. For some reason, probably because Yamaha’s in-house test rider Travis Preston has long arms, Yamaha moved the handlebars 16.5mm farther forward. Yamaha wanted to get the rider farther forward on the bike, but the width of the gas tank nullifies this. The majority of MXA test riders thought the bar setup was awkward when sitting and lessened their ability to get added leverage on the bars when there were pitch issues. The easy solution? We put the bar mounts back to where they were in 2019 (in the back hole with the bar mounts rotated forward).

The 2020 Yamaha YZ450F.

The 2021 Yamaha YZ450f only differs from the 2020 model  is that the fork guards are black, tank decals are different and, behind the white number plate backgrounds, the number plate plastic is blue.

The seat. With the stock seat, you feel like you are sitting in a hole—an unpadded hole. How unpadded? In 2019, Yamaha YZ450F increased the foam density by 16 percent. Guess what? They increased it by 10 percent more in 2020. They didn’t change in in 2021.  For our taller test riders, we ran a 20mm-taller GYTR seat (and we put the handlebars back to the stock 16.5-inches farther-forward position). This setup helped lessen the cramped footpeg-to-saddle height for tall riders; however, short riders hated this mod because the bars lifted their arms up. And with the tall seat, they couldn’t touch the ground.

(2) Maps. Yamaha has a dedicated button on the clutch side of the handlebars that allows the rider to switch between the stock map and a performance map (the performance map will be indicated by the button lighting up). As a bonus, you can change maps on the fly. If you do nothing, then both maps will have the identical stock map, regardless of the light. Yamaha is the only brand that allows you to change maps with your smartphone. The fuel and ignition maps have 16 programmable boxes, and you can change the fuel in 2-percent increments and advance/retard the ignition in 1-degree increments. Most MXA test riders preferred the TP-3 (Travis Preston) map over the stocker or the other pre-programmed maps (TP-5 and GC-1) on the Yamaha app. The Preston map (above) took away the jerkiness at low throttle settings and produced a much smoother overall powerband.

(3) Air filter. We hate the 2019–’21 Yamaha YZ450F airbox and air filter design. Yamaha uses a flat piece of foam that lies on top of the backfire screen like a piece of toast. Every time the engine pulses, which can be 10,000 times a minute, the air filter vibrates against the wire screen. The constant pulsing and suction dries up the air filter oil and eventually sucks dirt through the dry spot in the foam. There are two fixes.

The simple choice is to run a Twin Air YZ450F air filter (part number 152221). It features a much thicker foam filter plus a plug-in, top-hat style spacer that lifts the Twin Air filter off the backfire screen to lessen the repetitive pounding against the screen.

The second choice is better, but more expensive. Twin Air offers the best fix in the form of its Power Flow kit. It includes a new airbox sealing ring (that eliminates the backfire screen), aluminum cage (that goes inside the air filter instead of on top of it) and dome-shaped air filter (that replaces the piece of toast). If you don’t replace the stock air filter with the Twin Air design, be sure to check it constantly. If you see a white circle in the center of the air filter, re-oil the filter immediately.

It may be ugly, but without any other mods to our 2020 YZ450F this combination of a Twin Air PowerFlow kit, Travis Preston map and  jerry-rigged airbox cover, our YZ450F went from 58.04 horsepower to 60.83.

As a side note, we used a leftover, Twin Air, rivet-on, humpback, airbox cover from the 2018 YZ450F Power Flow kit to double the air volume of our 2020 YZ450F airbox—and gained several horsepower. 

(4) Gearing. In 2018 the YZ450F gear revved out too quickly, only to be met by a sluggish third gear. So, MXA switched the stock 13/48-tooth gearing for a lower 13/49 combination. We liked the gear ratios a lot better because they made third gear more accessible. When the 2019 model was released, lo and behold, Yamaha had adopted MXA’s “add one tooth on the rear” solution. The 2020 -2021 YZ450F still has the 13/49, and it is about perfect.

(5) Weight. At 238 pounds, the 2020-2021 Yamaha YZ450F is 3 pounds lighter than the very heavy Suzuki RM-Z450 but 15 pounds heavier than the 450 class’ lightweight champion, the 223-pound KTM 450SXF. You can’t do much about the majority of the bulk, but you would be well-served to focus on the unsprung weight. The first thing to look for is lighter wheels, tires, tubes, bars, seat foam and make a conscious effort not to add aftermarket parts that add weight.