Dr441

DR441

PERSONAL PROJECT

The making of a mini-Thumper

Suzuki's DR350 WAS INSTANTly popular with buyers, but after a couple of trail rides, many riders wanted more

horsepower. Companies like White Bros. quickly responded to this need. Herb Kane, White Bros. R&D Manager at the time of the DR’s debut, was directly involved with developing most of the company’s DR350 performance parts. Shortly after most of the DR parts were developed, Kane left White Bros. to join the R&D team at Mikuni. But his interest in the DRs remained high, so he decided to build a big-bore DR441 for his personal use.

Turning the 350 into a 441 required the use of a White Bros, replacement cylinder liner with a lOmm-larger bore and a WB piston with a 10.5:1 compression ratio. To insure against head-gasket leakage, the cylinder and head were machined to accept an Oring in addition to the copper head gasket. Kane then ported the head and installed 3mm-larger valves and bronze valve guides. A White Bros, high-lift camshaft, heavier valve springs and titanium retainers completed this part of the project.

A 36mm Mikuni flat-slide carburetor, taper-bored to 39.5/38/39.5mm, and a K&N air filter supply the engine with air and fuel. Large-diameter, stainless-steel headpipes and a WB Megalloy silencer are lighter than the stock exhaust system and provide another power boost. Heavy-duty clutch springs were installed so the DR’s pumped-up power wouldn’t be wasted in clutch slip.

With the DR441 engine now making 45 bhp, the chassis and suspension needed upgrading. A White Power shock replaced the stocker, while a 1989 Suzuki RMX fork with AMP Research springs added rigidity, increased wheel travel and provided more consistent damping. Kane also strengthened the lower shock mount and welded a steel glide plate to the frame’s lower tubes. An anti-chassisjacking AMP Link was added, which according to Kane, “greatly improves rear-tire hook-up.” EBC brake pads, a non-slip Ceet seat cover and a Tsubaki O-ring chain capped off the project.

When asked how much it would cost to duplicate his 441, Kane laughs and answers, “A lot.” Pressed for some figures, he says the engine work and parts would set someone back approximately $1600. Then there’s the suspension changes. A White Power shock goes for $450. Kane acquired a used RMX fork and triple clamp-new, these pieces cost $2245.

Does the heavily modified DR work? Is such a project worth the cost? Kane thinks so. As proof, he entered his 441 (with long-time Pro Jim Holley doing the riding) in the USGP Four-Stroke support class, where it finished seventh overall, first under-600cc bike. Kane is even talking about building another DR, this one with a more radical engine. And he wonders just how light he can make the chassis.

People who build project bikes always have one thing in common: They’re never satisfied.

Ron Griewe