Speedy Siegl’s 100,000-Mile DRZ!

Suzuki DRZ400 Supermoto

The Little Thumper That Could…

Suzuki’s DR-Z400S (dual-sport) and DR-Z400SM (supermoto) may not be the lightest, most powerful thumpers on the market, but these 400cc machines have earned a cult following with riders all over the globe. The DR-Z hold its value amazingly well, and words like charisma, character, and fun are often used to describe the bike — traits that trounce horsepower and power-to-weight ratios in the final estimation. MCN‘s consensus says it all:

“Brilliantly competent dual-purpose motorcycle…The Suzuki DR-Z400S is bit heavy for true off-roading, but greenlaners love it for its indefatigable charm.”

Suzuki DRZ400 Supermoto

Enter Isaac Siegl, the designer and machinist behind Speedy Siegl Racing, a Seattle-based company that manufactures lightweight, race-inspired parts out of 6061 aircraft-grade aluminum and sponsors three of the area’s top vintage class road racers. Last year, we featured Isaac’s retr0-styled Husky 610 supermoto. Now Isaac is back with something you don’t see too often:  his 2003 DR-Z400S, which has more than 100,000 miles on the clock!

Suzuki DRZ400 Supermoto

While the bike may look fairly stock on the exterior, it has an array of modifications intended to increase performance, handling, and durability. When it comes to performance, Isaac is an adherent to the Lotus philosophy of the legendary Colin Chapman:

“Add lightness.”

Suzuki DRZ400 Supermoto

So he did, managing to shave some 37 pounds from the DRZ’s curb weight. The bike has been dyno-tuned and now makes 35 rear-wheel horsepower — slightly more than the factory machine makes at the crank. More importantly, this supermoto has been ridden — and ridden hard — all over the Pacific Northwest:

“I have crashed it twice and gotten right back up, ridden it through a snow-induced gridlocked city on sidewalks, hydroplaned across flooded roads, explored hidden trails and secret tracks and the bike just keeps going!”

Below, we get the full story on this little thumper that could.

Suzuki DR-Z400 Supermoto: In the Builder’s Words

Suzuki DRZ400 Supermoto

DRZ history:

This bike has had quite the life! My friend who owned it before me racked up 35,000 miles of highways, trails, and race courses all over northern Washington and Canada. He used to ride it to races all over the northwest, compete (and place well!), and ride it home.

I purchased the bike in 2010 as a “ran when torn apart” bike for $1800. I had just bought a house, and all of my other bikes were having major failures, so I had to do the most I could with the least amount of money I could. After I put it back together, it’s first ride was as a backup bike when I went camping in the dunes that summer. After I blew up my RM500 I put some miles on it and was immediately impressed! I had recently fallen in love with supermoto bikes, so that was my direction. However, I just can’t leave anything stock…

Suzuki DRZ400 Supermoto

Everyone knows that the DRZ isn’t the most powerful supermoto bike, and also pretty heavy. As reliability was my goal with this build, I did something I almost never do: left the engine alone! I focused all my performance modifications on reducing weight and improving traction. Happily the bike came with an FMF titanium exhaust! I removed as many unnecessary parts as possible, ran a smaller battery and installed a kickstarter. A friend offered up a set of supermoto race wheels, brakes and front caliper from a Yamaha YZ250 track bike and I happily snatched them up. The forks are the same type as DRZ400SM, but they were sourced from an earlier RM125 at half the price. After many headaches getting the bearings set up for the axles and the wheels spaced appropriately, I had a supermoto bike! After a little dyno tuning it was ready for duty.

Suzuki DRZ400 Supermoto

This bike has been ridden all around the northwest by myself and others, and I’m pretty certain that NOBODY has been easy on it! Even with the highway gearing it will wheelie regularly, and sees 7000-8000rpm for long periods of time. Seattle’s roads are notoriously terrible, so having excellent long-travel suspension is awesome. I have crashed it twice and gotten right back up, ridden it through a snow-induced gridlocked city on sidewalks, hydroplaned across flooded roads, explored hidden trails and secret tracks and the bike just keeps going!

The longevity of this bike is part luck, and part meticulous maintenance. Regular fluid level checks and changes are a major part of that. Regular valve checks every 6 months. I go through a rear tire, chain and sprockets annually. Front tires every other year.

Suzuki DRZ400 Supermoto

On a bike like this, the world becomes your playground.

Build specs:
  • 2003 DRZ400S
  • Excel rims with Talon hubs
  • Braking front and rear wave rotors
  • Braking 34mm front caliper
  • Nissin 11mm front master cylinder
  • 2001 RM125 forks, re-valves with racetech springs
  • Re-valved rear shock
  • Modified airbox
  • Removed battery box, relocated battery to airbox (now a speedcell battery)
  • Removed coolant overflow tank, added smaller custom unit behind radiator.
  • Removed cooling fan
  • Lightened motor mounts and fabricated new rear motor mount from aluminum
  • FMF Ti4 exhaust
  • Renthal aluminum bars
  • Zeta hand guards
  • Rigid Industries led spotlights for headlight
  • Upgraded regulator/rectifier
  • Acewell gauge
  • Specs:
  • 35rwhp
  • 34 ft-lbs torque
  • 285lbs wet

Follow the Builder

Web: www.speedysieglracing.com
Instagram: @speedysieglracing
Facebook: @speedysieglracing



  1. Could have just bought a 701. DRZs are the most boring motorcycle ever made!

  2. I have a street legal 2005 “e” model, that I absolutely love.

  3. Could have bought a Hayabusa …….

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