03. Chasing Artisan-Quality Welding With Robots

Welding rarely gets the spotlight, but for Otohito Yamazaki—an engineer with deep welding expertise—it’s a core part of YZ450F quality and reliability.
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Yamazaki first became involved with the YZ more than 20 years ago, around the launch of the YZ450F. After time working on supersport models like the YZF-R1 and R6 and handling frames for overseas models, he returned to the YZ—setting and resetting welding on the assembly line, touching up welds, and performing final inspections. He moved into his current department four years ago.

For the 2026 model YZ450F, Yamazaki was responsible for everything from developing new welding techniques to bringing them onto the production line—ensuring the flagship model meets the standard expected of it.

Yamaha uses robots for welding, but consistent quality isn’t automatic. Rapid heating and cooling causes thermal distortion—the metal expands and contracts. The YZ series uses pulse welding, but that can increase heat input and distortion, sometimes requiring workers to rework welds.

So, for the YZ450F, the team adopted wire feed control. Welding with lower heat input reduces thermal distortion, reduces rework, and makes it easier to guarantee quality.

They could pursue new technology because manufacturing and production were aligned on the same goal: improve welding precision and reduce “valueless” re-welding work. Yamazaki’s team dug into welding conditions and jig precision. (A jig holds the frame during welding—if it lacks precision, even tiny thermal strain can allow the frame to move.) The team also developed a jig solution to address that problem.

Yamazaki’s image of “beautiful” aluminium welding is clear: a bead with uniform, scale-like patterns—consistent in height, without waviness. A highly skilled human can adjust speed and wire as heat builds, using experience and feel. A robot, however, runs at the same speed and conditions and can’t naturally respond as the frame heats up—so recreating that artisan-quality bead is difficult. That challenge was the point.

Yamazaki believes the team achieved it. By finding the right conditions across factors like speed and frequency, they moved from weld beads that were thin and flat to beads that are softer and thicker—visually sturdier, and fitting for a competition model.

The improvements didn’t stop at appearance. They reduced weight by 80 grams, reduced rework welding (helping delivery times and costs), and Yamaha notes that the 2026 YZ450F price remains the same as the 2025 model.

At the production site, the mission is to faithfully reproduce parts refined through development—but Yamazaki and his team also share a constant urge to add value: make it lighter, make it stronger, make it better. Even small gains matter if they help deliver a better product to riders.

Racing keeps that energy alive. Yamazaki follows results closely. To him, pro riders are “users” too—and seeing rankings, race photos and the bike in action brings pride to everyone involved. The welders and inspectors on the floor are watching as well, reminding each other: if it’s going to fly high, it has to be welded right.

Yamaha has many “fortresses” protecting quality. Yamazaki sees his team as a fortress in the welding domain—working so riders can enjoy the bike with peace of mind. Weld beads might not draw attention, but he hopes people will see them as part of what makes a YZ a YZ—and value them accordingly.

The Stories

1. People Ride It For Fun

When people think “development”, they often picture styling and design. But there’s another crucial part of the process: evaluation. Inside Yamaha’s First Vehicle Experimentation Department (YZ Gr.), evaluation means riding the bikes—testing engines and chassis in the real world, then judging what works, what doesn’t, and what needs to change.

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2. An Engineer Who Never Stops

If the frame is the bike’s skeleton, the engine is its heart—and Kitahara Naotetsu is the coordinator overseeing the full scope of YZ engine evaluation. Engine testing isn’t just ride feel. It includes measuring engine-only performance, checking functionality (oil circulation and pressure), evaluating reliability through durability tests, measuring noise to meet race regulations, assessing starting, and more. Kitahara describes himself as a “jack-of-all-trades”—someone looking at everything, managing everything.

4. Guardians of Quality

Takayanagi Kenji works in quality control. His role is to establish, maintain and manage quality standards for each new-model assembly process. He plans and implements measures to prevent defects and recurrences, and drives improvement activities by analysing quality data. Two influences led him to Yamaha Motor. One was his older brother, who worked for the company and was involved in motorcycle inspections. The other was personal history: Takayanagi attended Yamaha Motor’s soccer school as a child—back in first grade, over 30 years ago. That familiarity helped shape his desire to join.

5. I Love My Job

The YZ series of motocross competition models is sold globally—strongest in North America, but also spanning South America, Europe, Oceania and Asia. The riders are just as varied as the map: professionals in AMA Supercross, the Motocross World Championship and All Japan, plus weekend riders enjoying family rides or solo sessions. Some stay with YZs for life. Some ride them simply because it makes life better. And the YZ, in turn, is built by people inspired by those riders.

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