2006 Suzuki DR-Z400 Project Bike | Motorcyclist
Zach Bowman

2006 Suzuki DR-Z400 Project Bike

Step one: Blow up the engine

There are some people who can walk through an antique store swinging a sledgehammer over their head like a hickory and steel ribbon dancer and not so much as nick a vase. My buddy Sam is one of them. I am not. Entropy follows me around like a sad-eyed hound. Professionally maintained machines will fall down and die at my feet the second I get near, and it’s so common that I’m no longer shocked by the pieces of metal that come raining into the drain pan or the wheel bearings that go firing off into the weeds while I’m near. I just look around for the closest set of tools and set about making things right again.

So it was a bit of a surprise when Sam threw a leg over my recently acquired 2006 Suzuki DR-Z400SM for a rip around the block and did not immediately return. When I found him, he was winded from pushing the bike the half-mile from where it died. You never really appreciate internal combustion until you’re the one providing the power, lugging an irrationally heavy dirt bike up the same fierce hill you’ve throttled up time and time again.

2006 Suzuki DR-Z400

Aftermarket goodies like a set of dirt wheels, a pipe, and more made the bike a compelling buy.

Zach Bowman

This is not where I thought I’d be when I bought the Suzuki out of West-by-God Virginia for $2,000 in February. At the time, it seemed like the right move. The bikes are notoriously stout, with documented engines enduring well over 40,000 miles with nothing beyond valve checks and oil changes. This one had around 12,000 miles on the odometer, which wasn’t working due to a dead speedometer cable.

In fact, most of the bike’s systems were in need of attention. The fork leaked. The brakes were soft, it needed tires, and the seat, despite being covered in faux alligator skin, did nothing but hold rancid, moldy water. I waved all of this off in part because I knew that I’d be replacing or improving all of those parts regardless of what DR-Z I purchased, and partly because it ran well, pulling like a little thumper should. It also had some excellent equipment already bolted on.

2006 Suzuki DR-Z400

The bike had lived a hard life. Evidence of multiple downs, on pavement, were everywhere.

Zach Bowman

It began life as an SM, which meant it came from the factory with a fancy Showa inverted fork. Someone also ditched the restrictive factory exhaust for a Yoshimura RS-3, complete with a header. Wide pegs, Zeta hand guards, a big Clarke tank, and a Trail Tech headlight were also present and accounted for. There were no SM wheels, but the set of cheap 18/21 wheels were all I wanted anyhow. The bones were there. I paid the guy and brought the bike home.

I began by getting the bike roadworthy, starting with the suspension. A trip down to Christiansburg, Virginia, to visit the guys at Go Race took care of the very hammered fork and tired shock. Both got custom-rate springs, bushings, oil, and seals. I continued bashing my credit card with new brake pads and a fluid flush, neither of which did much to address the soft pedal and lever. I blamed it on tired internals, rebuilt both master cylinders and calipers, and threw on a set of braided-stainless lines, which eventually did the trick. The bike had spent at least a year outside, and that time had been brutal on the cables. Both the throttle and the clutch were stiff and gritty. Rather than try and rehab them, I opted for an inexpensive set of Motion Pro replacements.

2006 Suzuki DR-Z400

Why a DR-Z? Because Virginia offers some of the best dual-sport riding in the country.

Zach Bowman

The bike came with a set of ancient, rock-hard Dunlop D606 tires front and rear, and while they provide excellent grip for a DOT dirt tire, they have a painfully short life on tarmac. I’ve long been a fan of Heidenau’s K60 Scout for good 50/50 rear option, but switched to a Continental TKC 80 up front for a bit more grip. Both are long-lasting, and stand up to miles of pavement. I also threw that terrible seat cover and rotten foam in the dumpster in favor of a Seat Concepts kit. The optional water barrier should keep the thing from turning to a sponge, and recovering the old pan took less than an hour with an air stapler.

Rockbridge County

Virginia is packed with perfect DR-Z roads, including this hidden gem in Rockbridge County.

Zach Bowman

My early rides around town weren’t encouraging. No amount of adjusting could get the clutch close to operating correctly, and there was a terrible amount of clatter from the bottom end under hard acceleration. When I inspected the clutch friction plates and springs, I found them all within a hair of being out of specification. A $100 EBC kit, complete with springs and plates, fixed both the clatter and the adjustment.

But I was still left with what was effectively a bone-stock DR-Z, and all of the maladies that have pushed me away from the bike in the past came to the surface again on the first long ride of the season. The new suspension offered up a bit more confidence as a couple of buddies and I tackled a challenging Jeep trail, but the 400cc engine always felt overmatched by the bike’s 320-pound wet weight. In factory form, the DR-Z produces 32 hp at the crank, and while that’s fine for bopping around, it doesn’t provide the snap and crackle that makes a lightweight machine fun.

dual-sport bars

The wonder of the world viewed from behind a set of dual-sport bars.

Zach Bowman

Suzuki hasn’t significantly updated this model since it debuted in 2001, thanks in part to the fact that it’s grandfathered in under old EPA regulations. The second the company changes anything—gearing, displacement, fuel delivery, etc.—the machine has to be recertified, a process that can take years and cost millions. Fortunately, I’m not hemmed in by any such restrictions.

I was into the bike for a whopping $3,700 when a friend sent me a Facebook Marketplace listing. Someone was parting out an older KTM 400 EXC. They wanted $200 for that machine’s Keihin FCR 39 carburetor. It was in need of a complete teardown and rebuild, but came with a few hot parts already installed, including a remote fuel screw and an adjustable accelerator pump. The DR-Z’s stock Mikuni is the source of much of the engine’s lament, the CV design offering lazy acceleration at best.

FCR 39

The FCR 39 is a common performance modification, replacing the slow CV Mikuni with a legitimate pumper.

Zach Bowman

The internet is full of complete FCR kits for around $500, but I hoped I could be through the KTM piece for much less. I was wrong. A busted choke knob, a pile of jets, a complete rebuild kit, and the adapter for the Suzuki’s airbox cost me nearly exactly what a new kit would have set me back, plus a pile of nights trying to get everything right. For three weeks, all I did was install and remove carburetors on that bike. Repetition is the cornerstone of both mastery and madness, but after the 40th or so try, I realized I had the carb slide plate upside down. After inverting it, the bike ran and idled.

FCR 39

And everything was going so well…

Zach Bowman

It only took a bit more fiddling with jets to get the engine running correctly, and for the first time in my long experience with DR-Zs, the bike was fun to ride. The pumper carb delivered a beautiful hit of acceleration right off idle, making for easy clutch-up wheelies through third, even with the stock 41-tooth SM sprocket. I couldn’t say if it made any more power, but the FCR brightened the delivery considerably. It felt like a 400 should.

Two days later, it quit running entirely, leaving Sam on the side of the road. The postmortem wasn’t pretty. It turns out that a very small number of DR-Zs have valve failures at the 12,000–15,000-mile range. It usually happens on engines that have spent plenty of time at the deep end of the rev range. When I pulled the head, I found the remains of an intake valve gone rogue. The carnage was thorough. The head and cylinder wall were trash. Worse, the valve had managed to punch a hole through the piston, launching bits into the case and preventing the crank from making its full sweep.

FCR 39

The aftermath of a separated valve head.

Zach Bowman

It took a few days to plummet through the stages of grief, and to research my options. Complete, running DR-Zs can be had for as little as $2,000 all day long. A used replacement engine is, illogically, $1,500, plus shipping. A rebuild, complete with a new crank, bearings, cylinder, piston, and head, would be around $2,000 with me providing labor. At my lowest point, I considered simply parting the bike. In the end, I did what I always do: Looked around for the closest set of tools, and set about making it right. All of the parts for a 469cc big-bore/stroker build should arrive over the next few weeks. How good can a DR-Z be? We’re going to find out. Stay tuned.

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