Spanner | Hideki Hiratsuka

Up Close With Yohei Kojima's 2018 Works RM-Z450WS

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Photos and Words By Mike Emery | @emeryphoto

Team Suzuki Japan's Hideki Hiratsuka

Hometown: Mito City, Ibaraki Prefecture

Years Wrenching: 10

Rider: Yohei Kojima

Past Riders: Akira Narita, Cloud Toda

Believe it or not, motocross is not as popular in Japan as it is in the United States—even though the majority of the world's motocross bikes are produced on the tiny island country. That said, those who are involved in the sport—be they racers, mechanics, or support personnel—are a highly dedicated group of individuals. Such is the case with Team Suzuki Japan's Hideki Hiratsuka, who currently spins wrenches on the works Suzuki RM-Z450WS piloted by former All Japan National Champion Yohei Kojima. Hiratsuka's younger brother raced motocross, and Hideki learned the ropes by helping him all the way through his professional career. "I never tried riding or racing myself, because motocross is dangerous!" Hiratsuka said jokingly. "My job is on the other side, working on the bikes."

Through the years, Hiratsuka has worked for many different Japanese racers. "All of them are famous in Japan," he said. We first met him, though, when he worked for the late Cloud Toda during his stint as a Suzuki factory racer. Next, he worked for 11-time All Japan National Champion Akira Narita on the N.R.T. Yamaha team, before returning to the factory Suzuki squad as head mechanic, where he was paired with Kojima and earned the championship in 2015.

We asked Hiratsuka how being a factory mechanic on the Japanese series differed from the AMA circuit. "American mechanics must attend a lot of races and do so much traveling every year, and I think that is tough," he says. "But I think that the overall amount of work is not too different, even though Japanese mechanics have fewer races to attend. This is because of all the development testing we must do for future model development."

Hiratsuka's racer Kojima was sidelined with an injury when we visited the Sugo Sportsland round of the All Japan Nationals, so it seemed like the perfect time to snap some photos of the dyed-in-the-wool works bike and quiz Hiratsuka about as many specifics as he was allowed to share.

Works, Not Pre-Production: The RM-Z450WS that Yohei Kojima races is a true works bike. Though the bike is a good representation of what the 2018 production bike will be, it is not a pre-production machine, as it has many special parts that will never go into production. We were testing this race machine for five months in a very busy schedule, before the series opener. The bike is built specifically for Yohei and he has been involved in all of the tests, even when the bike was very rough.

Factory Power: The exact details about the RM-Z450WS engine are secret, but I can say that there is little difference between the power of this bike and a production machine. The tracks in Japan are smaller than America, so big power is not the most important—ease of riding is. Of course, depending on the race track, fuel injection adjustments, ignition timing, and other corrections can be made to make the bike perform ideally for the rider, but these specifications are all made to emphasize ease of riding, not the biggest power.

Old-School Cable: Though the team's second rider Kouichi Fukaya has a hydraulic clutch on his race bike, Yohei is very abusive on the clutch, so he prefers a traditional cable-actuated clutch. He has used it for many years and he knows the feel of a cable clutch for the starts and on the track.

Suspension: The riders are given their choice of suspension vendors, and Yohei prefers Kayaba components. His fork is factory KYB PSF2 air, and the shock is a works unit as well. His suspension is relatively normal in setting, as he does not prefer super stiff settings. The bike is set up with an emphasis on balance and rideability.

Working on Works: Because the level of production bikes is also high, there is no big difference in maintenance between a standard bike and a works bike. However, works bikes use a lot of special parts and lightweight parts, so we must keep exact track of the time on every part and replace them with regularity. In reality, there are many things that can still be used for a long time, so I will use them on Yohei's practice bikes.

Teamwork: I first worked for Yohei in 2005 at the San Diego Supercross. It was a last-decision for him to come to America and race, and we were both very excited. That first race ended with a big crash because he rode too aggressively, but since then he has become a smarter, more clever rider and racer. He is mentally strong, and that showed when he won the championship in 2015.

We rode their works Suzuki RM-Z450WS, CLICK HERE to watch a video!

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