2019 Factory Off-Road Bikes—Jacob Argubright’s Kawasaki KX450

Tracking the evolution of the Hare & Hound champ’s bike.

In its latest end-of-season iteration, Jacob Argubright’s Kawasaki KX450 doesn’t look much different than the one he started the season with.
In its latest end-of-season iteration, Jacob Argubright’s Kawasaki KX450 doesn’t look much different than the one he started the season with, but the experience he gained during the campaign led him to incorporate some significant changes that helped him win his first AMA National Hare & Hound Championship.Mark Kariya

The 2019 Kawasaki KX450 that Jacob Argubright used to win the Kenda/SRT AMA National Hare & Hound (H&H) Championship Series, presented by FMF, received a few changes as the season progressed.

After buying it and the initial test/familiarization rides, the off-road support/TBT Racing pilot made a number of changes to better suit off-road racing and those mods (examined in an earlier story) helped get him off to a great start in both the H&H and AMA West Region ISDE Qualifier Series.

Here’s his bike at the beginning of the season.
Here’s his bike at the beginning of the season.Mark Kariya

However, Argubright put most of his focus on the desert-centric H&H series where he won the first two rounds and led in points until Beta USA’s Joe Wasson won rounds three and four, putting them into a tie at the top. After round 5 (where 3 Bros/SRT Husqvarna’s Dalton Shirey won followed by Wasson and Argubright), Wasson carried a slim four-point lead over Argubright, 131-127, going into the summer break.

Returning from the break three months later, Wasson got another win with Argubright having to work extra hard coming from behind to get second and drop another five points.

Obviously, things needed to change and among them was the tendency for the KX450 to fire up slower than the 430 RR, Wasson taking advantage to sprint away in clean air.

To speed up starting on those dead-engine starts, he came up with a dual-battery system incorporating a pair of 12-volt units, each of which is smaller than the stocker.
To speed up starting on those dead-engine starts, he came up with a dual-battery system incorporating a pair of 12-volt units, each of which is smaller than the stocker. Other than fabricating new mounts and notching the airbox a bit, the only other thing he discovered he needed was a cord to charge one battery the night before a race since the standard charging system only provides juice for one.Mark Kariya

Knowing that the Beta team modified the 430s to run a pair of batteries, Argubright and his father devised a way to incorporate a similar setup in his bike—not easy on a bike originally designed solely for motocross tracks.

“I put two, smaller 12-volt [Antigravity XPS SC-1] batteries [into the top of the airbox, one stacked on the other though slightly staggered],” he shares. “I think they were four-cell instead of eight [as in the stock KX450 battery].

“It’s definitely a little above [my understanding], but basically, how the starting system is, I shouldn’t have any issues because there’s no solenoid [in the starting system].

“The only issue I’m going to have is eventually [during a long race], I’ll run out of [juice in] one battery [since the charging system is still stock and meant for one battery].”

To get around that issue somewhat, Argubright added an electric cord that plugs into a battery charger. That way, he can “top off” the battery the night before a race to ensure the pair has a full 24 volts to start with.

While he hasn’t run into symptoms of “over-juicing” the starter motor with double the voltage and it’s not a guarantee—his start at round 7 was fairly abysmal—so far, so good. “I actually put in a new starter motor just to be sure on the last [round], but over the off-season I’m going to put the original starter on and see if I blow up a starter or anything.”

There have been instances of subframes breaking near the muffler mount on KX450s.
There have been instances of subframes breaking near the muffler mount on KX450s; Argubright broke two himself, one of those costing him a race. The solution FMF devised was a rubber grommet in the muffler mount hole plus a steel strap adding extra support between the mount and seat-mount bolt.Mark Kariya

Another issue that cropped up was subframe breakage near the muffler mount. In fact, that happened twice to Argubright before FMF developed a solution that, so far, has worked. In addition to a rubber bushing where the muffler mounts to the Kawasaki’s aluminum subframe, FMF provided a simple light-gauge steel “bracket” that runs from the muffler mount to the seat mount bolt on the right side of the subframe, thus adding support.   “That metal piece that FMF provides saved my whole race [when the mount broke at the Mint 400],” Argubright declares. “Along with that modification, I re-welded the tab and braced it so I wouldn’t have any more issues.”

The 2019 KX450 comes with aluminum footpeg mounting brackets, but Argubright found those began to wear excessively at the pivot bolt holes after 15–20 hours. The solution was replacing those with the steel versions that came on the 2018s.
The 2019 KX450 comes with aluminum footpeg mounting brackets, but Argubright found those began to wear excessively at the pivot bolt holes after 15–20 hours. The solution was replacing those with the steel versions that came on the 2018s.Mark Kariya

He also addressed two more durability concerns as the season went on, one of which centered on the footpegs—or more accurately, their mounting.   “Two things,” he says. “One, I lowered them to put me a little lower on the bike. Shockingly, I have long legs. (He’s about 6-foot-2, after all.) [Lower pegs] give me a little more room and it’s easier for me to keep my feet on the pegs.   “The other thing is the mount. The black mount is actually from a 2018 Kawi and that mount is made of steel where the newer one is made of aluminum. What happens is [the lighter aluminum one] gets really soft and after about 15 or 20 hours I have to replace it because the hole [for the footpeg pivot bolt] would get so egged out.”

After starting the season with wave-type rear rotors, Argubright found he couldn’t get through a race without the brake pads wearing excessively and unevenly so he found some regular-style replacements for $30 on Amazon and no longer has that issue.
After starting the season with wave-type rear rotors, Argubright found he couldn’t get through a race without the brake pads wearing excessively and unevenly so he found some regular-style replacements for $30 on Amazon and no longer has that issue. At the faster (primarily California) races, he runs 13/47 gearing, which puts the axle farther back for a longer wheelbase and more stability. For slower going, he runs 13/49, which moves the axle forward, shortening the wheelbase for easier turning.Mark Kariya

The second durability issue saw Argubright opt to run a non-wave-type rear brake rotor in order to preserve the OEM brake pads he prefers. (Yes, he sometimes drags the brake, something he blames on his size-13 boots. “I try not to—it’s one of my flaws,” he admits.)   “I think what’s happening is I’m getting the brakes so hot,” he opines. “The pads don’t have full contact with the wave [rotor’s surface so they] were becoming uneven, the pads were starting to bend [due to uneven heating]! It was pretty gnarly how sideways they would get. One pad would [wear] all the way down to the metal and the other one would be halfway gone [in a single race]. It was weird.   “The point is, with the non-wave [rotor] it should have equal contact all the way around and should have [the pads] wear better, which it does.”   He confides, “That is not a Galfer rotor. That is an Amazon rotor.   “I couldn’t find one [elsewhere] so they were like $30 on Amazon. I think it’s a cheap rotor, but it’s actually super-large. You can’t tell, but I think because it’s so large, it has more room for the heat to sink into it and I think it stays cooler.”

Lastly, there were suspension and gearing changes made over the course of the season.   “I was running a 13/47 at the beginning of the year. For a couple races like the Utah or slightly slower ones I ran a 13/49 and it was cool. It gave me a little more hit to it,” he remembers. “It also pushed the rear wheel forward which makes the bike turn a little bit better [due to the slightly shorter wheelbase].   “But ever since [round 7, the point-to-point starting in] Lovelock, [Nevada,] I went back [to 13/47].”   As for suspension adjustments, it was primarily location-dependent. “I started with my clickers at one [setting] and at the end of the year at Lucerne [Valley, California], I have them at the same point, but I have two different clicker settings [for other places]. Like at Panaca, [Nevada,] where it’s smoother and it’s a lot of washes, I actually slowed down the rebound two clicks and stiffened it two clicks [on compression]. That way I could push a little harder into the corners.”   He also learned that keeping the suspension fluid fresh can play a huge role in performance: “I felt like it was getting soft so [Travis Flateau of] TBT [Racing] was out there [at the final round in Lucerne] and because I had four races on the suspension oil, he freshened it up for me [with new fluid] and it was way better! I couldn’t believe how much more hold-up the bike had. I’d thought I needed a different suspension setting and I was going to have to update it. I should just keep my oil fresher!”   All of this will undoubtedly be valuable information when it comes time to begin defending his number-one plate in January. Before then, however, he has a few local races plus next month’s ISDE in Portugal where he’ll be campaigning a very similar setup.