Atk 604 Electrical Start
ATK 604 Electrical Start
CYCLE WORLD TEST
A Gentleman's Dirt Bike
WE HEAR IT ALL THE TIME: “I'D LOVE A BIG FOURstroke Single, but the damn things can be pure hell to start. Why doesn’t someone build a serious thumper dirt bike with an electric starter?”
Good question. And it’s also one that has recently been answered. Horst Leitner, founder and owner of ATK, a company that's been building custom four-stroke Singles since 1983, has added an electric-start, four-stroke to his line of twoand four-stroke models for 1989.
Lest people think of the electric-start 604 as only a “playbike,” Leitner quickly describes the Electric Start’s race record to date: “Greg Zitterkopf has won the Open class at several California motocross tracks, racing against well-known riders on the latest 500cc, two-stroke Singles; and he was leading the 1988 Barstow-to-Vegas race until a carburetor needle clip came adrift.”
Zitterkopf was just as excited concerning the new model, “It’s great for dead-engine desert starts. When the starting banner drops, I just touch the starter button, drop the clutch and peg the throttle.”
Zitterkopf made it sound so simple. But we’ve known Greg for many years; he is big, young, strong and fearless. Does a regular person need his size and strength to handle the extra weight of an electric-start 604?
No, but it would help if the buyer is going to race motocross. For desert racing or serious trail riding, the ATK 604 shouldn’t be considered too large and heavy.
Actually, the electric-start components only add an additional 1 5 pounds to the weight of the 604. And the necessary parts are spread around the bike to help mask the additional weight. The starter motor is a rather small unit that’s tucked into the lower front of the engine’s cases; the starter solenoid and tiny sealed battery live in the airbox; and the only hint of the machine being different is the rectifier that’s mounted in plain sight on the frame’s front downtube—the starter button is a modified kill button.
So how much does it weigh? ATK claims the dry weight as 262 pounds. On our scales, it weighed 264 without gasoline, and 292 with the 4.6-gallon fuel tank brimming. Comparing dry weights, the ATK Electric Start is 5 pounds lighter than an ’88 Honda XR600R. Still, 264 pounds is nearing the point where a serious rider might question the ATK’s ability to handle well. But assuming a bike that weighs this much must handle poorly would be a mistake.
Few motorcycles will match the 604’s straight-line stability across chopped ground. The single White Power shock, mounted on the left side of the bike without any linkage, performs great. But a good deal of the rear suspension's performance is the direct result of Leitner’s patented A-Trak Chain Torque Eliminator that’s mounted around the front part of the swingarm.
This device eliminates the engine's torque effect on the rear suspension. On a conventional chain-drive motorcycle, the suspension has a tendency to extend when power is applied. A similar effect is noticeable on shaft-drive streetbikes. But the A-Trak system neutralizes this effect.
The result is instantly noticed when accelerating up a grade strewn with square-edged holes; the normal reaction of a non-A-Trak-equipped motorcycle, even the latest and trickest one, is rear-wheel kick and harshness. With the ATrak, the rear suspension is nearly magical; the rear tire follows the nastiest terrain, the tire grabbing traction instead of kicking into the air. Comfort and control under these conditions are unmatched.
A White Power 4054 inverted fork is standard equipment up front. This is the older, non-cartridge design that ATK modifies before installation. The fork works well but it doesn’t match the smoothness and control of the externally adjustable cartridge model. The cartridge model will probably become standard ware after Leitner gets a chance to test it and determines internal valving specs, but for now, the proven version is standard.
ATK has redesigned its plastic side number panels and fuel tank for 1989. The new, larger fuel tank has dropped sides to place the weight of the fuel lower on the bike.
Track racers, concerned about being hindered by the large fuel tank, need not worry; this tank is nice and slim in the area where the rider grips with his knees. And for track racing, there’s no need to fill the tank to its limit: just pour in a gallon or so, all of which rides low on the chassis.
ATK 604
Like the nicely finished plastic parts, every component of the ATK Electric Start boasts of quality. A chromemoly steel frame is made to ATK’s specifications; the big Rotax engine bolts into the frame without the need for mounting plates; the wheels are standard KTM items that feature no loose spacers; and disc brakes are stock, a conventional single disc at the front, a countershaft-mounted rear unit.
Like the unique A-Trak system, the ATK-designed countershaft brake is special. A small, steel rotor is bolted to the countershaft sprocket and a single-piston hydraulic caliper is mounted to the engine by aluminum brackets. A steel-braided hose, only a few inches long, connects the caliper to a master cylinder that’s mounted to the rightfront frame downtube. A small, plastic reservoir is mounted higher on the same tube.
This unique brake-reservoir placement lets Leitner add another bit of trickery to his machines: an aluminum brake pedal that pivots at its front. Forget about snagging the brake pedal and twisting it under the footpeg on the 604. It can’t happen.
It’s also doubtful that many people will ride the ATK and complain about a lack of power. In its stock condition, with a Supertrapp silencer, the engine produces a claimed 43 bhp at the rear wheel. An accessory cam is also available for $145 that boosts the power to 48 bhp. Our test bike had the optional cam already installed, and this engine makes power—a lot of power. Lofting the front wheel at most speeds is easy, yet the bike isn’t wheelie-prone. The balance front to rear is perfect. We couldn’t find a hill> large enough or a sandwash deep enough to to bog or slow this engine.
ATK
604
And, of course, starting is sweat-free. A quick push of the starter button has the ATK making beautiful sounds almost instantly, hot or cold. Clutch pull is a little on the heavy side, but most riders didn’t find it objectionable. Getting a feel for the bike while the engine warms, the rider is aware of being way up there on the firm seat, despite a fairly low seat-height measurement. The answer comes in the amount of rear-suspension sack: only 2.5 inches, instead of the normal 4.0 inches on other bikes. This difference is the result of ATK’s unique shock placement that eliminates linkage arms but requires a very heavy spring rate.
This tall seating and the rather tall and heavy Rotax engine give the bike a decidedly top-heavy feel while stopped and at lower speeds, but it is less noticed at higher speeds. And despite its short 58-inch wheelbase and steep 27-degree head angle, the ATK 604 doesn’t corner with the quickness or agility of a 500cc two-stroke motocross bike. The ATK will corner quickly, but it requires a different technique. Directional changes are best effected when riding the bike in a more-normal, four-stroke style—heavy use of the throttle, with much of the steering dependent on sliding the rear wheel. Simply diving into a berm and turning the handlebar doesn’t work well.
The tall seating position is a little clumsy when trail riding, too. Riders over 6 feet tall can plant both feet firmly on the ground at rest, but anyone shorter has to depend on tippy toes or one foot.
These small complaints are quickly forgotten, though. This bike is pure fun to ride. And the electric starter just adds to that fun factor. But we wondered how the bike would start after a tip over; you know, one where the bike stops with the fuel tank heading downhill, and it stays in that position until the rider regains his breath. We simulated this situation by laying the bike on its side, tank downhill, petcock on, for about one minute. After standing the bike up, the engine turned over a couple of times and was then running.
We also questioned the tiny sealed battery’s durability when trying to start an engine that decided it really didn’t
want to run. And we were curious about the starter’s ability to start the engine in a cold climate. Leitner was quick with his replies: “I've sold a couple of these to guys who live in Colorado and they say the bike will fire right up, no matter how cold it is. As for the durability when trying to start a cranky engine, I don’t know. Let’s find out.” He pulled the sparkplug wire and grounded it against the head, then pushed the starter button. Afer one minute of cranking, he let the battery rest for a few seconds and then held the button in for another full minute. At the end of this “test,” the starter motor was still spinning the engine quickly. Leitner then connected the plug wire to the sparkplug, grinned and pushed the button again. The exhaust let out a muffled pop and the engine was running. If there is any weakness to the electric starting system on the ATK 604, we couldn’t find it.
The electric-start ATK is certainly an amazing off-road motorcycle, although with a retail price of $6980 plus options, it isn't going to be attractive to everyone. Still, for the true four-stroke lover who has been jilted by the hardstarting antics of past thumpers, this is a bike that could go straight to the heart. ®
ATK
604
SPECIFICATIONS
$6980
